# Suspension fork shortening



## GrayJay (May 16, 2011)

I have now built four different kids bike forks from 26" forks. First was an early manitou that I shortened for my daughters 20" bike, http://forums.mtbr.com/families-riding-kids/novara-pixie-20-project-853041.html 
I then tried modifying a rockshox Mag21 into a 24" fork. I did eventually get the mag21 working but it was a fairly difficult conversion that I would not necessarily recommend repeating, details in the pixie thread above. Next up, I shortened a late 90's manitou spyder 26" fork into a 24" fork. Details of this one are at 
http://forums.mtbr.com/families-riding-kids/trek-mt220-24-mod-build-894279.html and http://forums.mtbr.com/families-riding-kids/24-air-fork-884666.html#post10782625 
The spyder came out as the best working fork I have made yet and it is really lightweight at below 1300gr compared to currently available 24" forks that start around 1600gr. THe spyder fork however was never sold in great numbers so finding one to do a conversion might be tough.

Another candidate conversion fork that was produced in large numbers starting back in 1997 and onward for several years was the Rockshox Indy series. I recently picked up an Indy S fork from local bike co-op for $8 to test out as a kid 24" conversion. The salient feature of the Indy forks that make them a good 24" candidate is that the dropouts are inline with the fork leg (not offset on tabs in front like on the Judy), and the lower portion of the slider casting is solid and has plenty of thickness to re-work into new shortened dropouts. The Indy forks came in various flavors from the lowly Indy S that used steel stanchions, 45mm travel and weight 1510gr, the intermediate Indy C, the Indy XC and SL that both utilized aluminum stanchions, more sophisticated spring/elastomer stack, 60mm travel, friction dampening and weighed as little as 1220gr (for the threadless steer tube SL). More info of the Indy forks can be found in the 1997 & 1998 RS product catalogs at Rock Shox Museum The slider casting on all the indy fork flavors is nearly identical, so even though I started with an Indy S, I may later try to upgrade it with lighter stanchions and innards from one of the better forks. Looking at the specifications for similar era RS forks, the quadra 21R fork looks very similar however it was reported that these are hollow (like the mag 21) and cannot be shortened. 
The bike this fork is going onto belongs to a neighborhood friend of my daughters. He recently got a used Hotrock 24 that was about 8-10 years old. 








I was fairly impressed with the overall quality of this bike in comparison to some of the junky parts I have seen on other similar kid bikes. This era hotrock featured butted aluminum frame tubing, decent aluminum crankset with an aluminum outer ring, quick release aluminum hubs, a nice kids saddle, decent looking specialized tires, sun CR18 rims and aluminum seatpost, stem & handlebars. Original weight on the bike was just under 25 pounds, not too bad as a starting point for a modification project. Downside for this bike were an ugly kickstand plate welded onto the chainstay and it came with twist shifters that are hard for kids to operate. The single biggest downside to this bike however was the craptacular RST suspension fork;








When I got the RST free of the bike, the bare fork weighed a full 1930gr on its own. It actually had an aluminum steer tube but RST must have packed the innards of the fork with lead or depleted uranium as weight ballast.

Here is the original rockshox Indy 26" fork before I got after it 








First step in the conversion is drilling a pilot hole at center of the new axle location, 25mm upward from the center of the original axle location. 








The outer side of the fork leg casting is scalloped inward and entire leg gets thicker as you move away from the fork tip, slightly complicates fabrication of a new forkend at correct distance from the brake post to suite 24" rim. If you lack access to a machine shop mill, easy solution is to use a 3/4" carpentry spade bit to cut in and level out the casting in order to form a new fork end. When you make the pilot hole, dont drill out to full size of the 9mm axle or the hole will be too big for the spade bit to stay centered. Use the spade bit to drill until you form a 3/4" circle into the tapered outer side of the fork that is parallel to the original dropout. There is a "tooth" on outside diameter of the spade bit that causes it to drill the outer ring a bit deeper than the main part of the bit. 








Once you have the new circle formed using the spade bit, you can hacksaw off the excess fork length. Drill the center axle hole out to 9mm and hacksaw slots to end of fork. Use sharp hand files to shape the dropout, get it all leveled out. End result should form a hood recessed into the casting that will provide enough clearance for the quick release when the axle is seated in the drop-out. I also used a dremmel tool cutter bit to help square off and clean-up the the hood area. 








The inside of the fork casting is tapered but not scalloped like the outside. It is easy enough to just use a large 1/2 round hand file to level out the casting above the new axle hole so that the hub axle nuts have a flat dropout surface to bite into. The new fork end needs to be parallel, you don't want the quick release to tighten down onto a tapered fork end or the wheel can easily fall out if the skewer loosens and slips. Also make sure to file the inside-to-inside dimension of the fork ends to exactly 100.0mm. If the inside dimension is different from the hub locklut-to-locknut dimension, it will cause binding of the forks movement. 








End result, a decent quality and lightweight 24" rim brake fork;








The Indy forks are fairly easy to tune for stiffness with different springs and MCU bumpers. For kid use, just running a spring stack in one side is plenty. Final weigh on this fork was 1490gr, over a 400gr weight savings from the original RST fork at very minimal cost and it was a fun project. With no other modifications, this hotrock is now weighs 24.0 pounds. This was done just using a lower-end OEM grade Indy fork, but there were definitely nicer and lighter Indy forks available that could be converted in same manner. The conversion would be even easier if you had access to a drill press and mill but it can be done with just hand tools and some patience! End results are that it would be hard to tell that this fork was not originally factory made as a 24" without looking at it up-close.

I would encourage others to give a try at shortening 26" forks rather than spending $$ on a new 24" fork that is still significantly heavier than what you can easily fabricate yourself. Post your projects here, keep this thread going to share fork-mod ideas.


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## Fargo1 (Oct 19, 2012)

GrayJay said:


> Original weight on the bike was just under 25 pounds, not too bad as a starting point for a modification project.
> View attachment 926718


Wow 25lbs. That is light for a kids 24" with susp. Everything I've seen, including the new Hot Rocks are closer to 30lbs. I'd love to find 2 old Hot Rocks like that.


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## mussy01 (May 23, 2007)

Subscribed. I hope to add content to this thread in the next couple months. I am getting ready to begin rebuilds on a 24" Giant XTC Jr. and a 24" Marin Bayview Trail for my two daughters. Thanks for the great write-up on these options as the 26" air fork route seems like a great solution for weight and performance!


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## GrayJay (May 16, 2011)

Searching around a bit, the specialized bike the neighbor kid got appears to be a 2006, only year that it used the same Sun CR18 rims. (the hotrock A1 FS model for other years appear fairly similarly well equipped). 
2006 Specialized Hotrock A1 FS - BikePedia 
I would be curious to find out the bare frame weight if anyone ever strips one down. I dont think many other kid 24" bikes actually use butted tubing, would be interesting to see if this frame is significantly lighter than other similar size non-butted frames.

The boy that owns the bike did several kid cyclocross races on it this fall, the shortened fork worked great.


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## Birdman (Dec 31, 2003)

GrayJay,

How far does the solid aluminum portion extend on those Indy forks? I'm looking to fabricate a light weight 20" fork, but I'd be surprised if the fork legs had an extra 3" of solid aluminum at the bottom.

Thanks,

JMJ


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## GrayJay (May 16, 2011)

Solid portion of the Indy slider casting ends at the green line I drew above, about 2" above the original 26" dropout location so not enough material present to shorten the fork by 3" for a 20" wheel. There is also a threaded bolt hole tapped further down into the casting. I did not hit the hole when I shortened 1" for a 24" wheel but it was likely close.



Birdman said:


> GrayJay,
> 
> How far does the solid aluminum portion extend on those Indy forks? I'm looking to fabricate a light weight 20" fork, but I'd be surprised if the fork legs had an extra 3" of solid aluminum at the bottom.
> 
> ...


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## GrayJay (May 16, 2011)

Birdman said:


> GrayJay,
> I'm looking to fabricate a light weight 20" fork, but I'd be surprised if the fork legs had an extra 3" of solid aluminum at the bottom.
> Thanks,
> JMJ


For a 20" fork, an early 90's manitou is a good conversion that is more strait forward to implement than carving up the Indy fork ends and they can be even lighter weight. My daughters 20" manitou came out at 1130gr with steel springs, probably could be even lighter if you were to instead use elastomer bumpers and replace the heavy-duty steel steer tube with a lighter tube (aluminum or thinner steel). Manitou conversion previously detailed in thread http://forums.mtbr.com/families-riding-kids/novara-pixie-20-project-853041.html but I will paste it here too in order to consolidate fork mod info in one thread.

As far as the manitou fork, Credit and inspiration for the idea goes to forum user TigWorld as in thread; http://forums.mtbr.com/families-riding-kids/why-kids-bikes-so-heavy-701515.html#post7974542 and the great write-up he did at FAQLoad - 20" front fork build
I was just initially a bit intimidated by TigWorld writeup tutorial because of the heavy use of lathe, milling machine tools to accomplish the needed modification. I decided to go ahead and give it a try and accomplished the same conversion using little other than a hacksaw and hand file, the 20" manitou came out great.

My commentary/process corresponding to the steps listed in the TigWorld tutorial are;

Step 2-
Probably hardest part of the entire conversion is just getting the pressed-on cast fork end (dropouts) seperated from the forks lower tubes. Without access to machine tools, I just hacksaw cut the lower tubes about 2cm above the dropout casting (Higher than TigWorld so I would have more of the outer tube to grab), then used a handheld hacksaw blade and to make a couple of slits along the axis of the remaining stub of the outer tube that remained pressed into the dropout (dremmel grinder might also be helpfull here). THe slits helped to weaken and de-tension the super-tight press fit between the tube OD and the dropout casting ID enough that I could eventually partially collapse the tubing stub by proding with a dull chisle and pliers. To help pull last of the tubing stub out, I next I drilled a couple of holes in the tubing, just above the dropout so that I could pass a large nail through the tubing and (loosely) hung the assembly on the through-nail, over the open jaws of a vice and then used a punch to to hammer the dropout down and off of the weakened tubing stub.

For Tig's step 4, I just used a hacksaw to cut the remaining tubing to length (not a lathe) and then used a machinst square and hand file to get the ends nicely square. Note that there is no need to reduce the OD of the tubing any, it is perfect OD for a tight press-fit into the dropouts.

Step 5- I used a spare hub to help align and start the lower tube into the dropout but finished it off by just hammering the lower tube into the dropout as I didnt have a press big enough for length of the tube, worked fine. Along with loctite, I drilled a 1/8" hole in the assembled dropout + tubing and added a pop-rivet to ensure it would never loosen and separate. (The press fit is extremely tight, rivet probably unnecessary, I didnt see evidence that manitou even used loctite for original assembly).

THere a a lot of variations of how the early manitou 1,2,3,4 fork design changed. I think Tig's manitou sport fork was actually based on a manitou 2 or 3, not a 1 as the original manitou 1 (1990-1991) fork (pre-answer design) had a much different looking arch between the lowers. The manitou 1&2 and perhaps some of the later years lower end manitou models put the elastomer stack below the stanchion tube while the improved model 3&4 forks moved the elastomers up to the top, inside the stanchion. For a short fork conversion, stay away from any of the manitou (1 or 2?) forks that used externally butted steel stanchion tubes, the butted section of the stanchion would be too loose when the stanchion is shortened and the butted section re-located up near the forks upper seal/bushing. ( I did manage to use a butted steel stanchion by sectioning a piece from the middle and brazing a reinforcement sleeve inside but it was a lot of work and hassle). The very earliest Manitou 1 fork used non-butted steel and some later models utilized unbutted aluminum stanchions that make a 20" conversion much easier and are approx 200gr lighter.
For any kids manitou conversion, just run a spring on one side of the fork, no need for 2 springs or urethane kabobs with a small kid. You can either stick with elastomers which also provide reasonable dampening but I opted to convert to using a steel coil spring and stretched it to around 60mm travel. There is enough inherent friction in the operation of the fork that it dampens OK with the light spring pressure. On those manitou forks with the spring below the stanchion, if you do go to just using a spring on one side, note that the plastic bushing at bottom of the stanchion is normally held in place by spring pressure so you will need to use a short bolt and large washer to keep the bushing in place without spring pressure. This would not be needed on a manitou 3 or 4 where the spring is located upward, inside the stanchion. THe later forks have bushing holder that keeps them retained without spring pressure from below.

Overall, the manitou was a huge improvement on the too-stiff 4+ lbd junker RST fork that the bike started with and the vintage CNC fork components also have high bling factor!

As an aside, my other previous experience with modifying early manitou forks was exact opposite direction of fitting them to kid bikes, I have modified and setup a couple of manitou forks as fatbike forks for use with 4" snow tires. The versatility of the basic manitou design is great for offbeat DIY adaptation.
http://forums.mtbr.com/fat-bikes/fatbike-front-suspension-718335.html#post8180121

Update- I recently swapped out the steel stanchion tubes on the fork for some aluminum manitou 3 stanchions, saved 200gr of weight on the fork (around 1130gr now). Together with addition of mow-joe tires, 12/18 spoke wheels, slightly lighter crank and bottom bracket; the complete bike is now just under 20 pounds. The thick steel steer tube on the manitou fork is fairly heavy. I have a spare early manitou crown where the 1" steer tube can be unbolted from the crown, I am thinking that for kid use replacing the heavy steer tube with either an aluminum tube or thinner steel would likely drop another chunk of easy weight and still be safe. At the same time I could also swap to setting it up as a threadless steer tube and change out the quill stem for a lighter aheadset stem.

Here are a couple of recent actions shots of the 20" manitou. My 6-year old did her first cyclocross races this fall on the bike. Thanks in part to the light fork, she is actually able to lift an carry her bike over the barriers, most other kids on heavy bikes take 2X as long to get past the barricades because they are unable to even lift their bikes, resort to lifting just one end at a time or throwing the bike over the barrier.








Here she is on the way to a 2nd place finish, just beaten out by her older sister.


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## GrayJay (May 16, 2011)

One more fork conversion project for another neighbor kid.
Started with this Gary Fisher;







This bike was unfortunately heavy at around 28 pounds. Super heavy adjustable angle stem, heavy steel handlebars, nutted hubs and another craptacular RST fork that weighted 1970gr and was full of rust (completely non-functional).








I upgraded to a RS Mag21 fork that I shortened. It was a difficult conversion that I wouldn't recommend (the magnesium sliders are hollow just above the regular 26" fork end). Benefit is that can get you an 24" air fork with 60mm (long travel conversion) and actual hydraulic dampening. I think the final weight on this fork was somewhere around 1400gr, take that RST & spinner! 
I also changed out the heavy bars, stem, threaded headset to aheadset and replaced the nutted front wheel for a 12 spoke radial w/ quick release hub that I put together. Above changes shaved 3.0 pounds off the front end of this Fisher. I was on a low project budget (all volunteer project, no $$) but I would suspect that this bike could still easily loose another 4 pounds with lighter tires, crankset, bottom bracket, seatpost and a rear cassette hub wheel.


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## GrayJay (May 16, 2011)

My most successful fork conversion project was to adapt a '97-'99 era manitou spyder 26" fork as a 24" fork. I found one of these for dirt cheap at local coop and thought it had potential as a kid fork. The spyder is V-brake only, no disks. Reasonably lightweight construction with 28mm aluminum stanchions and uses an aluminum steer tube. This fork uses elastomers and coil springs stacked together for around 65mm of travel, and it also has a separate primitive dampening mechanism in one of the legs to provide some degree of dampening for the spring.









1450gr total weight for all original parts as found. I removed the elastomers and springs from one leg to soften the fork for my 65 pound rider, a much more suitable stiffness for her to compress. I will probably do a bit further tuning to dial it in by changing/modifying the elastomers or by converting to a coil spring in place of the remaining elastomers since there is also separate dampeing mechanism to keep it from becoming a pogo-fork.








One of the reasons I selected this for was for the configuration of the fork ends which are directly inline with the stanchion tubes (instead of protruding forward from the fork). Started my 24" wheel conversion by drilling small holes through the fork that are 25mm upward from center of the original axle location.








I used a carpentry spade drill bit that was same outer diameter as an axle nut, centered it in the pilot hole previously drilled and roughed-in a new dropout from the existing metal, hacksawed the excess length off and then used dremmel and hand files to finish the new dropout.

Resulting 390mm Axel-to-crown fork length correctly lines up a 24" rim with the brake post and is shorter than a 26" fork so doesnt jack-up the front end and slacken the headtube angle.








Resulting weight after shortening and removing the elastomers & springs from one leg was 1283gr, approx 1 pound lighter than sourcing a new (and expensive) 24" air fork, nearly 2 pounds lighter than the junk coil-spring forks that most 24" bikes come with. Staying with V-brakes also saves weight and expense over a disk brake conversion and in my experience V's are plenty strong.









In hindsight, if I were to convert another of these forks I would not shorten it by a full 25mm. When shortened by 25mm, there was still plenty up upward brake pad adjustment range left on the V-brakes I am using. Shortening by 25mm started to place the new axle location up in the fat tapered portion of the slider casting and made it more work to produce a new flat fork-end for the axle to securely bolt into. It would have been easier fabrication work if I has setup to have the brake pads fully upward on the arms, so that I could get away only shortening the fork by only 15-20mm instead of 25mm, this would keep the new fork end down on the flatter, skinny section of the casting, reducing the need to carve out so much of the tapered portion of the casting to produce a new flat dropout.

Thread for rest of this MT220 project bike is at;
http://forums.mtbr.com/families-riding-kids/trek-mt220-24-mod-build-894279.html

Satisfied customer!


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## Birdman (Dec 31, 2003)

Thanks for consolidating all the info. This should be a sticky.

I'd love to fab a 20" air fork, but I'll keep my eyes peeled for any good candidates.

I have access to a manual mill and lathe, so i'm not too intimidated by the fabrication part. 

Many thanks - JMJ


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## DWDW (Oct 7, 2005)

Awesome work! Definitely inspired to try this.


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## GrayJay (May 16, 2011)

In another thread, Melchiondia asked about using a Manitou 3 fork as the basis for a 20" project fork. I started off by converting a manitou 2 fork which has steel stanchions and locates the springs/elastomers at the bottom of the sliders, the bottom of the stanchion tubes simply press directly down on the spring/elastomer. This is a really simple design that works fine but for the Manitou 3, they moved the springs up inside the stanchions so that pre-load adjustment can be made from top of the fork instead of bottom as is required by the manitou 2 design. Kids dont really need to be constantly fiddling with the pre-load adjustment so the early M2 design is still fine. I did later make a slight upgrade to my M2 based fork by swapping in the shortened aluminum stanchion tubes from a dead M3 fork, saved weight but I didnt alter the M2 lower spring arrangement.








Modifying a Manitou 3 or 4 fork for kid use should be no problem. Here is a picture of the guts of a manitou 3 fork that I partially disassembled. In this design, there is a push rod that goes from bottom of the fork up into the stanchion tube. The spring is sandwiched between the top of the push rod and the top cap of the fork that is screwed into top of the stanchion, through the crown. Below the stachion tube, there is C-clip that rest on slots cut into the push-rod, this clip serves to hold the bottom-out bumper elastomer. The top of the push-rod had two protruding disks. The lower disk normaly serves to hold the top-out elastomer bumper (inside the stanchion tube). The upper disk is the spring seat for the main spring elastomer stack. In order to shorten a M3 fork, you will need to shorten both the slider/lower and also the stanchion tube by 3" for a 20" wheel. The M3 stanchion tubes have a bushing holder that is pressed into the bottom of the tube and have threads cut in the top of the stanchion tube to retain the top-cap. You cannot shorten the stanchion by cutting off the top of the tube (as in a M2) since you would loose the threads but the bushing holder can be knocked out (from above) and then re-installed once the stanchion is shortened. 
Just shortening the stanchion tube would leave minimal length remaining for for the spring or elastomer stack if you made no other changes. In order to regain most of the original length of the stanchion tube for the spring, you need to modify the push rod. Cut off and remove the top spring seat disk and excess rod length, cutting just above the lower top-out disk so that both the main spring and the top out bumper will now be pushing on opposite sides of the lower disk. Using a short top-out bumper will also help to regain length for the spring. 
One of the reasons I use a steel spring rather than elastomers is that I found that for a given free length, a steel spring can provide more suspension travel than an elastomer stack. You would need a longer elastomer stack to provide the equivalent travel of a spring and there just is not enough room in the shortened stanchions. FOr my daughters bike, I am just using a single steel spring in one side, but thinking it through; using two lighter springs (one each side) should provide more travel before having the spring stacks solid.

Another modification that occurred to me; if you were to shorten the lower slider by full 3" but only shorten the stanchion tubes by 2", this would allow the fork to extend out by 1" further when unloaded so would give even more length for a spring and also could provide 1" of extra travel. Manitou forks dont have much travel to start with (somewhere around 50mm I think) so a "long travel" conversion could help to provide more cushioning. Only other modification that would then need to be performed then is to cut 2 new slots in the pushrod 1" lower to move the bottom-out C-clip in order to adjust for the effectively 1" longer stachion tubes. M3 forks have plenty of overlap between the top and bottom bushings, kids riders should have no trouble with the resulting fork stiffness/rigidity.

-------------------------
Advice for avoiding e-bay scalpers and finding old manitou forks at reasonable cost:

Some sellers may be asking crazy prices but I've seen old manitou forks sell at much more reasonable prices on e-bay in open unreserved auctions. I would say that more than about $50 is unreasonable for a vintage manitou fork. Vintage collectors may buy and hoard them to but these forks are entirely obsolete these days, much better forks are available for adult MTB riding. I've acquired several old manitou forks from local bike co-op. They either sell them dirt cheap or else try to throw them away if non-functional so I always check their recycling bin for free parts donors. You can probably also buy a complete older bike locally on craigslist or at garage sales to harvest the fork and other donor parts for much less $$ than the e-bay scalping prices. Also try asking your local bike shop to keep an eye out for them on upgrade jobs, most shops probably just throw these old forks away if not working. Common problem is that the old solid elastomers melt after 10-15 years so loose all spring action, either need new elastomers or else simple conversion to coil spring. Newer forks used MCU elastomers which are lighter and full of tiny bubbles, seem to last longer than the solid melting polyurethane elastomers. It is a very simple and strait forward conversion to exchange the elastomers for a steel spring harvested from another fork or check among generic springs at a good hardware store.


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## melchionda (Sep 25, 2012)

I went to every local bike shop in the area. I found two manitou forks... One is a Manitou 2 with 1-1/8" steerer and the other is a Manitou 3 with a 1" steerer.

I'm thinking of buying both and moving the fork crown from the 2 to the 3 so that I can have the proper steerer diameter. Although I have a suspicion that the owner of the Manitou three is going to try to price gouge me.

It was funny searching for these forks. No one at the shops knew that they had them. I playfully bet them that they would have one and low and behold I was correct twice!


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## XJaredX (Apr 17, 2006)

I am watching a Manitou 4 on eBay right now for a 20" conversion, thank you much for all the tips! I wouldn't even have known this possible without this thread.


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## melchionda (Sep 25, 2012)

LOL! I think there are several of us watching that one.


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## TigWorld (Feb 8, 2010)

When I made a 20" fork from a Manitou 1 Sport fork, I had trouble getting replacement elastomers (because of the hole needed through the middle), so I ordered some polyurethane rod and made some. That fork is now on its third kid and still going strong.

For a 24" fork, I used a Mag21, but instead of modifying the lowers, I made some brackets that dropped the brake mounts down enough to line up with the 24" rim. GrayJay's approach results in a much neater end product, but the brackets are removable if you ever want to reverse the process. I also modified that Mag21 into a long travel and solo air version that was much more suitable for a kid.


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## GrayJay (May 16, 2011)

melchionda - easy to switch the crown and legs between forks if it proves necessary. You might start by getting the M2 fork, see what it looks like and see if you can make it work first.

Only caution is that some (if not all) of the M2 forks had steel stanchion tubes with external butting, complicates shortening the stanchions since you dont want the narrower butted section of the stanchion passing through the upper bushing. 
The lower slider legs of the M2 and M3 forks are very similar, just the configuration/location of pre-load adjusters changed. If you start with the M2 fork and get the lowers shortened, the will be useable with either the M2 or M3 stanchions. 

cheers


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## melchionda (Sep 25, 2012)

I'm beginning to think that getting a manitou three or four fork for a reasonable price is impossible. The manitou 2 that I got isn't going to work. The steerer is too short and I'm dealing with the tapered stansion issue. For 120 bucks I can get a spinner air fork Someone paid 89 dollars for that Manitou 4 on eBay. I can't believe someone would pay that much.


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## mussy01 (May 23, 2007)

What are your thoughts on a 1996 Rockshox SID 80mm v-brake fork with a 420mm axle to crown as a replacement for a 24" fork. I can get one locally in pretty good condition for $100. I haven't yet measured either of the two 24" forks I have and I realize I'd need to find/make an adapter to drop the brakes down to the 24" rim.

Thanks for your thoughts.


Sent from my iPhone using Tapatalk


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## GSJ1973 (May 8, 2011)

mussy01 said:


> What are your thoughts on a 1996 Rockshox SID 80mm v-brake fork with a 420mm axle to crown as a replacement for a 24" fork. I can get one locally in pretty good condition for $100. I haven't yet measured either of the two 24" forks I have and I realize I'd need to find/make an adapter to drop the brakes down to the 24" rim.
> 
> Thanks for your thoughts.


My thoughts. If I were me I would get the new RST First Air 24" fork for about $250 shipped, and this fork is going to be way better than anything produced in 1996. No mods necessary and 1600 grams. V brake and disc mounts.

By the time you factor _your time_ it takes you to do the conversion, not to mention if you drilled/cut it right you might be better off buying a proven fork already on the market with 2014 air cartridge technology. What is an extra 250-300 grams on a fork? Focus your weight loss in the wheels where it really matters.


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## mussy01 (May 23, 2007)

GSJ1973 said:


> My thoughts. If I were me I would get the new RST First Air 24" fork for about $250 shipped, and this fork is going to be way better than anything produced in 1996. No mods necessary and 1600 grams. V brake and disc mounts.
> 
> By the time you factor _your time_ it takes you to do the conversion, not to mention if you drilled/cut it right you might be better off buying a proven fork already on the market with 2014 air cartridge technology. What is an extra 250-300 grams on a fork? Focus your weight loss in the wheels where it really matters.


Hey GSJ1973,

Thank you for your thoughts and recommendation on the RST First Air 24" fork. I'll have to spend a bit more time researching that option and the features it would offer. For those that might come across this later, here is my thought process on considering the older SID.

- Weight: The current owner of the 96 RS SID provided me a weight of 1174 grams. There would be a bit of additional weight in the v-brake adapter. I should still come in below the 1600 gram limit but it's going to be much lighter than the existing fork on the bike(s).

- Performance: One of the minuses with this old of a SID is that it lacks dampening or rebound control. Big plus for the RST First Air fork especially if my kids are on this bike for 2-3 years. My question on dampening is whether or not this feature for a 8-10 year old is worth an additional $150? I image I should still be able to manually change the air pressure around in order to find a good fit for the weight they are at.

- Cost: $100 vs. $250 vs. other. I'm sure there is a degree of getting what you pay for in this equation, which is what we as adults evaluate on our own builds. For $100 I feel like I'm getting a healthy weight and performance gain from the existing heavy, coil sprung shocks on the bikes today. I'm not sure today's technology is going to give me incrementally more benefits in my application relative to the cost. Another cost consideration is maintenance/repair on the SID. I've been told it's in great condition but if it does need serviced, might be a challenge to find the right seal kit.

Maybe one of the newer 24" forks is a good option for me to consider on one of the bikes that will be around longer term. I've got at least one more kid to pass down a 24" to and another on the way. Will make that evaluation once I pull everything apart and get a better feel for the individual frames weight/geometry.

Thanks again for everyone's thoughts!


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## TigWorld (Feb 8, 2010)

I've given this F1rst v SID thing a bit of thought here. If you're in any way handy, then get a used SID, give it a rebuild (full service kits are still readily available and cheap) and with the money you save over the F1rst, build a good 24" disc front wheel. This will be a far superior setup to a v-braked F1rst. Also, when your kid grows out of 24", you can use the SID with a new set of 26" wheels. This is exactly what I have done over the past 12 months. If you can, try for a newer SID (2005-2007). It will be in every way superior to the RST fork.


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## GrayJay (May 16, 2011)

mussy01 said:


> What are your thoughts on a 1996 Rockshox SID 80mm v-brake fork with a 420mm axle to crown as a replacement for a 24" fork. I can get one locally in pretty good condition for $100. I haven't yet measured either of the two 24" forks I have and I realize I'd need to find/make an adapter to drop the brakes down to the 24" rim.


Looks like SID forks were not introduced until 1999, so the 1996 date might be wrong? Sid had disk mounts so probably easier to just use with a disk wheel than to fabricate a disk mount. If it really is from 1996 and is V-brake only, it does not sound like a SID. RS top fork from 1996 was a Judy, perhaps that is what you are looking at?


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## GrayJay (May 16, 2011)

GSJ1973 said:


> My thoughts. If I were me I would get the new RST First Air 24" fork for about $250 shipped, and this fork is going to be way better than anything produced in 1996. No mods necessary and 1600 grams. V brake and disc mounts.
> 
> By the time you factor _your time_ it takes you to do the conversion, not to mention if you drilled/cut it right you might be better off buying a proven fork already on the market with 2014 air cartridge technology. What is an extra 250-300 grams on a fork? Focus your weight loss in the wheels where it really matters.


Incase you missed it, there are already dozens and dozens of other threads going that discuss the options for purchasing expensive, overweight and underperforming new forks for kids bikes. This thread is for discussing alternative DIY approaches to better performing forks. Playing with modifying bike parts is very much a hobby. If you try to rationalize the time you spend on a hobby as a loss in a cost comparison, you are entirely missing the point of having hobbies. If I were concerned about the loss of time involved, I certainly would not have volenteered to convert several bikes for other kids in the neighborhood and I would not have bothered with the time to document the process here so that others can take inspiration and contribute.


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## mussy01 (May 23, 2007)

GrayJay said:


> Looks like SID forks were not introduced until 1999, so the 1996 date might be wrong? Sid had disk mounts so probably easier to just use with a disk wheel than to fabricate a disk mount. If it really is from 1996 and is V-brake only, it does not sound like a SID. RS top fork from 1996 was a Judy, perhaps that is what you are looking at?


As I was looking for additional info I came to the same conclusion about the model year. It does not have dampening so I'm sure that will help differentiate a little between the years. I went ahead and picked it up this morning. Weighed in at 1,117 grams with the titanium brake bosses.

Looking forward to going through it and learning more about the internals. The search continues for a 2nd option. I will continue to consider the 26" fork shortening.










Sent from my iPhone using Tapatalk


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## jh_on_the_cape (Jan 12, 2004)

I just wanted to counter that if you actually pay someone to do the work you did: build a wheel, rebuild a fork... it's way more expensive than getting a 24" wheel.
I bought a spinner air fork. Not as good as a SID but worked right out of the box much better than what came on my son's bike. Having a new wheel built, buying a disc hub and spokes, then having a fork rebuilt is $$. I paid $150 for the spinner fork. I could not find a decent SID for that.
It's like saying 'Why buy a new car for $25k when you can get an old broken down one for free and fix it up?' It takes time and expertise. 
Now if someone gave me a SID, I might tackle it... but I just wanted to get it going.
Finally, if the bike is going to be handed down to a younger sibling, I wanted to set it up so no parts would move up to the next bike.
The first 26" bike will have a SID, though. Great fork for light people (kids).
You should sell a kit with a rebuilt SID, a front disc brake and a 24" disc wheel. How much would you sell it for, over what you paid for the parts????


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## GSJ1973 (May 8, 2011)

GrayJay said:


> Incase you missed it, there are already dozens and dozens of other threads going that discuss the options for purchasing expensive, overweight and underperforming new forks for kids bikes. This thread is for discussing alternative DIY approaches to better performing forks.


"Better performing forks" is where I challenge you. I've owned both and can comment based on experience. Have you owned a RST First 24 air? I had a 2004'ish era SID 26" back in the day and I would rather ride a 24" 2014 RST product any day of the week (with only 60mm travel) over those SID's of old.

I'd gladly accept the 300 gram weight penalty over drills, saws, and chopping down fork legs, and spending $100+ on 8-10+ year old technology but that's just me.

Just some alternative perspective that there are now really good products on the market - RST First Air and Spinner Air 24".


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## TigWorld (Feb 8, 2010)

You'll need to show us what's inside a RST F1rst before I'll believe that it offers better suspension performance than a properly setup 10 year old SID. What's the damper? Any shims inside or simply port-orifice? What's the parts availability like? Repair manual online? etc. I have no idea about any of these things because its next to impossible to find any information online about these RST forks. For me that's an immediate turn off. My kids are riding their bikes alot and I can't have a bike out of action for a fortnight because I'm waiting on a set of seals or some other minor part.

Suspension forks require regular maintenance. There's nothing wrong with a second hand fork provided it is not mechanically damaged. Replacing oil and seals is the sort of thing manufacturers recommend at fairly regular intervals (some as short as every 50 hours). So what's the big deal with doing that when you get a second hand fork? You'll have to do it in a several months anyway even with a new fork.


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## GSJ1973 (May 8, 2011)

TigWorld said:


> You'll need to show us what's inside a RST F1rst before I'll believe that it offers better suspension performance than a properly setup 10 year old SID. What's the damper? Any shims inside or simply port-orifice? What's the parts availability like? Repair manual online? etc. I have no idea about any of these things because its next to impossible to find any information online about these RST forks. For me that's an immediate turn off. My kids are riding their bikes alot and I can't have a bike out of action for a fortnight because I'm waiting on a set of seals or some other minor part.
> 
> Suspension forks require regular maintenance. There's nothing wrong with a second hand fork provided it is not mechanically damaged. Replacing oil and seals is the sort of thing manufacturers recommend at fairly regular intervals (some as short as every 50 hours). So what's the big deal with doing that when you get a second hand fork? You'll have to do it in a several months anyway even with a new fork.


Good questions. I've not gotten to the point of taking it apart in 15 months he has had it on his bike nor has it required servicing the way the Rock Shox of old do. I still have canisters of Judy Butter and Slick Honey on my work bench from the old Rock Shox days.

Down side is 60mm of travel, the SID's are 80/100.

If/when the RST needs service, I will take it apart and post pics what I find.


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## tigris99 (Aug 26, 2012)

I'm coming up on probably having to do a 24" bike later part of next season as my son is getting close to out growing his 20".

All this nodding forks for a 24"... Do u realize the little difference from 24 and 26"??? I understand v brakes being of concern in some cases. And for some doing the custom work is fun, hell I love working on our bikes.

But im doing my research as moving him to 24" also means getting one with disc brakes.

Normal 24" forks blow that come on most bikes. Will be researching and setting to buy a set of forks that I can shorten the travel easily so that a-c is close. Being our local trails a bit slacker head angle will be hugely helpful as lots of hills and fast flow on the decents. But there is a line there that will affect him on the rest if I let it be too slack. Won't be too hard being 60-80mm is plenty on a 24" (I ride 100mm and rare I can use it all and takes a really wrong landing off a drop to bottom out).

Look at it this way take a 29er with xc geo so ht is steeper. Now take a 26"/27.5 with trail/am geo. Smaller wheels, smaller wheel base, even with slacker geo is going to be faster in the tight areas. Plus more stable at speed especially when descending. But I look at my sons bike differently than I look at mine. Making him more stable with better performance allows more confidence. This has worked very well thus far and since rebuilding his 20" (wish I could have gotten forks too but couldn't justify for 1.5 more seasons) making it insanely lighter, faster, and better quality parts throughout. This has made him progress by leaps and bounds in a short time.

Also a new model fork you know parts will be available for years to come. And hell seal kits aren't expensive in most cases, so buy a couple to have in hand.

Now this is opinion and my veiws only, wanted to add another view to this as food for thought. More food: so many parents have nice 1500-2500 bikes yet buy their kids WalMart bikes or brand name bikes that honeslty aren't all that much better performing than a WalMart bike??? Spend less on yourself for biking and more on ur kids. Or do like I did, work fair amount of overtime just for the purpose of redoing his mt60 into a bike even im proud of (and him for helping with alot of wrench time)
Sent from my Nokia Stupid Phone using Tapatalk


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## goldenaustin (May 30, 2011)

All very interesting and valid pros and cons with the last several posts. I personally went with a 2000 SID and now I'm waiting for the seals and travel adjust spacers to come in. It'll be about $150 total with just fork and parts. This doesn't include the Alex-20/Novatec/Sapim parts that I'll be building up as well as the disc brakeset. So as you can see, it'll definitely cost much more than if I got the RST F1RST and kept the stock wheelset and v-brakes. He's also not going to be able to ride it right away. However, if I didn't already have all the tools and desire to wrench and learn, as well provide a learning opportunity for my son, then I certainly would've gone with an aftermarket 24" air fork. For us, we find it equally fun to work on bikes as it is to ride them, which I understand is not necessarily the case for everyone.


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## melchionda (Sep 25, 2012)

So I'm back to working in those manitou forks. I found a manitou sport fork with a nice long thread less steerer and aluminum legs. So I'm working on that one. The elastomers are a sticky greasy gooey mess. I've spent the last two days taking it apart and cleaning it. Had to get creative to figure out how to loosen the Allen bolts down inside the fork tubes. Eventhough the bolts are loosened the legs are still seized inside the lowers because I guess the elastomers have melted and dried like a glue. I have both of the forks partially disassembled and soaking in degreaser right now. Hopefully that helps a little.


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## GrayJay (May 16, 2011)

melchionda said:


> So I'm back to working in those manitou forks. I found a manitou sport fork with a nice long thread less steerer and aluminum legs.


Does this fork have the elastomers up inside the stanchion tubes or down in the sliders?


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## melchionda (Sep 25, 2012)

The Forks are a Manitou 2 and a Manitou Sport. The Sport I believe came out the same year as the Manitou 2 or 3. It has the design of the two but uses the aluminum legs of the three. The Manitou Sport doesn't have the rebound adjustment and so was cheaper. Both of these forks have the elastomers in the bottom of the fork legs. The elastomers are a real mess and are going to take some work to clean out. Why anyone would want one of these forks for anything other than cutting it up is beyond me! When I raced on a manitou three in the 90's the only way to get it to work was to put speed springs in them.


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## wpgbike (Jan 6, 2015)

Grayjay, I'm currently building two 24" wheel bikes for my twin boys. I'm using Gary Fisher Precaliber frame for one (not sure of the year) and a Specialized Hotrock 24 (2005). The front fork for the Precaliber came in at 2.1 kg approximately, so I've picked up one Indy SL fork to modify and looking for a second. Thanks very much for your thread on this topic, it wouldn't have occurred to me to shorten a 26" fork. If you don't mind, I may have a few questions for you as I go along.


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## GrayJay (May 16, 2011)

wpg- post some pictures as you go!


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## wpgbike (Jan 6, 2015)

So, my first Indy SL fork arrived, and it is not what I expected. It measured 1,523 gr. on the scale vs. the "advertised" 1,220 gr. As I'm purchasing this for it's light weight as well as ability to be shortened, I'm quite disappointed. In addition, it is a threaded version. It appears as though a prior owner has put the exterior legs (forgive my lack of knowledge) onto the uppers and maybe internals of a Judy XC or something similar.

I have another one on the way that I have good information on, it should be fine, but I will still need to find a second one for my other son.


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## GrayJay (May 16, 2011)

wpg- bummer this one weighs so much. graphics of the fork look correct for a '97 indy SL. They omitted the cantilever brake cable hanger (v-only) in 1998. Info on these at;
Rock Shox Museum & 
service manual at suspensionforkparts - Rock Shox Manuals

The 1220gr claimed weight is specific to the threadless steer version which used an aluminum steerer, if yours is threaded it is steel and likely makes it a bit heavier but shouldnt account for being 300gr overweight. If the steer tube is long enough and frame size is small enough, you still might be able to use it with a threadless stem, just ensure that the bottom of the stem is well below the height of the old threads so that you are not transmitting torque from the handlebars/stem directly though the stress riser of the threads that could cause the steer to sheer off at the threads. 
Weird that it would weigh even more than the lower end indy C that had steel steer and steel stanchion tubes. I dont think any of the parts (except possibly the elastomers) from a judy fork would interchange to an indy. The Judy had larger diameter stanchions (28mm vs 25.4mm) wider spacing between the legs, a wider crown and completely different cast lowers (dropouts on protruding tabs instead of inline with the stanchions).

You should go ahead and disassemble the fork, see if there is anything weird with the internals that makes it so heavy such as if previous owner replaced the elastomers with heavier steel downhill springs. I think that the cast lowers should all be very close to the same, you can practice the dropout shortening modification with this fork first, if it goes well then you can then interchange and use the lowers on another lighter fork should you get one, I dont think the lowers will weigh different.


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## wpgbike (Jan 6, 2015)

Thanks for your advice Grayjay. I'd looked at the Rock Shox Museum info, that's where I'd seen the 1,220 weight. That's also where I'd seen a crown from a Judy that looks a lot like the one on this fork. In any case, my hunt continues for a replacement.

Here is a photo of the second Indy SL. I have not picked it up yet, so do not have an accurate weight on it.









In order to keep the geometry the same as the existing setup, I understand I need to keep the A to C measurement the same. I'm assuming I measure from the middle of the axle, but where on the crown should I measure to?


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## GrayJay (May 16, 2011)

Looks as if the second indy S is threadless, hopefully will weigh less. With the Indy forks that have crowns with removeable stanchions (retained by pinch bolts), you can interchange the crown with one from a mag21 should you need to change to a different steer tube size, such as going from 1" threaded to 1-1/8" threadless. (mag 21 used same 1" stanchion size and width spacing). 
Measure the A-C from center of hub up to bottom of the headeset crown race. A 20mm A-C difference will change the frame seattube and headtube angles by 1° (steeper for a shorter A-C.


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## wpgbike (Jan 6, 2015)

My second Indy SL arrived, weighs in at 1,237 g before modification. I will be redoing at least the MCU elastomers inside as I'm sure they're probably past their prime. My sons each weigh roughly 55 lbs, and I'm hopeful that I would be able to remove the internals from one side of each fork and have both a lighter and better performing fork relative to their weight. Has anyone done this before, and how did it work out? Does it have any effect on performance (thinking unbalanced suspension action, rather than weight)? Thanks


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## GrayJay (May 16, 2011)

Much better for the weight. Runnings the spring in just one side works fine, many forks came factory equipped that have a spring on only 1 side. 
I found several forks with MCU that were still fine after 15 years, the earlier style solid urethane elastomers are the ones that deteriorate badly. 
One thing you can do to try to tune MCUs for a very light rider is the drill out a larger hole through the center so that there is less of the elastomer getting compressed.


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## wpgbike (Jan 6, 2015)

I have a new wrinkle to overcome with the second Indy SL, the lower internals including the MCU is seized in the lower leg (see photo). The LBS says they'd be unable to remove it, and kindly offered to sell me a new fork . In any case, I have soaked it in Liquid Wrench for days to no effect. I have heard of other means of removal including pouring boiling water in to melt the MCU, using Coke etc. Does anyone have any experience with this? What would my best method of removal be? I'm leary of the boiling water idea as I don't want to have to scrape the inside of the tube to free it of melted rubber.


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## wpgbike (Jan 6, 2015)

Melchionda, were you able to get the melted elastomers out? I'm currently having the same problem (see below) and am looking for advice on successfully removing the goo. Currently I cannot get to the allen bolts as the mcu and other internals are still bound inside the leg.


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## GrayJay (May 16, 2011)

WPG-
If you have removed the top cap, spring and spacer; you should be looking down at top of the elastomer. Maybe try using a spade drill bit and drill through remains of the seized elastomer enough to get down to the allen bolts that hold the stanchions onto the lowers? 

I would imagine that really harsh chemicals like aircraft paint stripper might also be useful for melting the remains of the elastomer out of the stanchion tubes.


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## wpgbike (Jan 6, 2015)

Brief update. After far too much time invested, I have successfully cleared the internals of the Indy SL above, and am arranging a time to drill the holes for shortening. I have also located a second Indy SL which is on the way. Hopefully I can begin my builds next week.

Side note, the two bare frames (aside from the headsets) weighed as follows:

Gary Fisher Precaliber 12" - 1,570 g (1998 I believe)
Specialized Hotrock 13" - 1,640 g (1996)

Heavier than I expected, but I see no better alternatives out there for the price.

Looking like my builds will come in under 20 lbs.


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## GrayJay (May 16, 2011)

wpg- what did it take to remove the melted elastomers?


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## wpgbike (Jan 6, 2015)

In no particular order: Liquid Wrench, acetone, various drill bits, coat hanger, hex wrench extensions for pounding, brute force, etc. Basically, and please forgive my non-technical language, there were two "bushing"/seals that were seized in the forks, as well as the elastomers being seized themselves, lots of contamination in the fork leg. The acetone worked somewhat, but created a new problem in that there were small broken bits of elastomer blocking the hex bolt at the bottom of the leg. Time, effort, invention and force solved it in the end though. Not a process I would want to repeat, but I believe the resulting approximate 1,150 gr 24" fork will have been well worthwhile. Hopefully my second INDY SL is not similarly seized. I'll post photos once I've drilled and rebuilt the forks. Planning on painting the frames and forks to match.


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## wpgbike (Jan 6, 2015)

My first shortened Indy SL with new internals in one stanchion and nothing in the other weighed in at 1,206 grams.


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## wpgbike (Jan 6, 2015)

The second Indy SL ended up being seized considerably worse than the first. The bolt at the bottom of one stanchion that holds the stanchions to the uppers was completely rusted out, and I was unable to remove it. Additionally, the one stanchion leg had quite a bit of dirt and grit and rust inside, and was completely seized. In the end the only way to free the uppers (which I needed) from the lowers ( which I decided I didn't) was to cut them off with a hacksaw. Once cut, the stanchions still wouldn't separate from the lowers as they were so seized together. Much pounding, prying and liquid wrench later, I got them apart. Attached are a few photos of the end result complete with tools required, minus the hacksaw.

I have a third set of lowers which I believe at this point I will use without shortening.


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## wpgbike (Jan 6, 2015)

Complication number 79 or so and counting. The uppers do not slide into the third set of lowers, which were supposed to be the same size. Purchasing things at a distance has its disadvantages. Going into the lbs tomorrow to determine what actual size of lowers I need.


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## GrayJay (May 16, 2011)

wpgbike said:


> Complication number 79 or so and counting. The uppers do not slide into the third set of lowers, which were supposed to be the same size. Purchasing things at a distance has its disadvantages. Going into the lbs tomorrow to determine what actual size of lowers I need.


Did you figure out the issue? I would be surprised if RS changed the diameter of the stanchions (25.4mm / 1") or used different spacing between the legs.


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## wpgbike (Jan 6, 2015)

The spacing between the legs ended up measuring 2mm different between the lowers. The one set of lowers had the cantilever brake guide, which I gather was an older version. in any case, they could not be forced in, and I am left with finding another set.


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## GrayJay (May 16, 2011)

Spacing between the inside of the stanchion tubes is 81.5mm on the several Mag21 and Indy forks that Ive had. Weird that RS would have made a 2mm change to the spacing at some point. Only reason I can think is if they needed to thicken the dropouts then it would be necessary to also widen the stanchion & crown spacing in order to maintain 100mm hub width. bummer...


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## Paolo Zaccheo (Aug 26, 2013)

Thank to GrayJay for the ingenious idea!
My 6yr daughter has a 12kg Legnano 20" mtb with iron fork.
I tried to cut a Rock Shox Quadra 21R that was in garage but I gave up because the casting is hollow until the foot (sorry for my english ;-) ).
The manitou I found was too expensive but I like very much this Halson Inversion I bought for 50 eur.









I want to short it cutting the stanchions 2" over the foot, remove the tube and then reglue at the new lenght. Like you did for the Manitou.
Do you think could be OK?


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## GrayJay (May 16, 2011)

Bummer the RS quadra didnt work, it was probably a (hollow) casting that was similar or identical to the contemporary mag-21 air fork. 

I have never tried to disassembled a Halson Inversion fork but it does look promising. You might try using a pipe tube cutter (or just a hacksaw) to cut through the lower legs about 20-25mm above the top of the dropout, hopefully then the dropout casting will come off with the lower cut piece and then you can make a vertical cut in the short piece of leg and separate the dropout casting. Next, cleanup, re-insert and bond the casting back into the shortened lower leg. It might help to use some heat on any epoxy boding the casting to the lef if you have difficulty getting the casting separated from the cut-off lower tube. Alternately, the casting may simply be a close tolerance press-fit into the leg. Be careful to get the two dropouts aligned parallel when you re-install, try clamping the casting to a hub to keep them parallel. 

The spring for these forks appear to be elastomers, you can likely remove all the elastomer from one side of the fork to soften the spring rate for your daughter. Drilling a larger hole through the middle of the elastomer can also help to soften the spring rate. Be sure to inspect the elastomers to check that they are not hardened or deteriorated, replace if necessary. 

Post some pictures of your progress, Good luck!


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## GrayJay (May 16, 2011)

If you cannot find a manual, the original Halson patent has some useful schematics
Suspension for bicyles


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## Paolo Zaccheo (Aug 26, 2013)

Thank GrayJay!
The previous owner putted 2 springs for each leg. Not too bad... I have some elastomers and i try a combination, but only in one side because my daughter is around 50 lbs.

I measured with a wire inside of the leg and casting dropout go into 22 mm.
I cut 30 mm, tonight or tomorrow.

I ordered some light rims from Malvestiti, 310g

Ciao!


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## wpgbike (Jan 6, 2015)

So I have my two modified Indy SL's up and running. I put new elastomers in, with new long travel kits, with elastomers in only one leg. They are quite soft and bouncy, noticeably so compared to some of their competitor's forks when observed over the same terrain, maybe more than optimal. They do work though, and are very light, so I am pleased in the end. I have some video and photos that I will put up if I have time. One complication, in one fork I was only able to put in one retaining bolt at the bottom of the unit as the other was blocked/rusted out. We seem to be getting more upward movement in this fork now than before, so I will have to have a look at it in case the bolt has let go.


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## GrayJay (May 16, 2011)

GrayJay said:


> You might try using a pipe tube cutter (or just a hacksaw) to cut through the lower legs about 20-25mm above the top of the dropout, hopefully then the dropout casting will come off with the lower cut piece.


I was thinking that you were shortening this to 24" (507mm) wheel size, to go to 20(406mm) , you will need to shorten the fork legs a total of (559-406)/2= 76.5mm.


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## Paolo Zaccheo (Aug 26, 2013)

*Halson Inversion*

After some hacksaw and dremel works the casting is separeted from the stanchion. The casting go inside the tube 25mm

































Now I put epoxy but tomorrow she has a Race! Old fork for tomorrow

The old fork is 2100 gr. The shorted Halson is 1345 gr. Not too bad.


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## wpgbike (Jan 6, 2015)

*Indy SL mods*

Here are a few photos of the modified Indy SL's in action. These are my twins in action at our local race series recently.


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## Paolo Zaccheo (Aug 26, 2013)

*Halson Inversion*

I finally mounted the shorted Halson Inversion on the bike.














​
We are now at 10.2 kg. The original bike was 12.8 kg
Next steps are transmission and wheels.


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## GrayJay (May 16, 2011)

Paolo- Nice job converting the Halson fork, the final results looks great. The work needed to shorten this fork design looks fairly minimal and it could probably also be adapted to produce a 24"/(507mm) fork.

For your next wheel-building project, see thread; http://forums.mtbr.com/families-rid...-wheel-build-40lb-rider-need-help-891768.html


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## wpgbike (Jan 6, 2015)

My one sons uppers could only be attached by one anchor bolt, and inevitably this broke. I've now replaced it with another Indy SL, this one with the Englund Air Cartridges, under 1200 grams. Huge improvement.


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## Walt (Jan 23, 2004)

*Another idea?*

I was thinking of just building some clamp-on dropouts that could slide up and down the fork blades as needed (ie, on an old SID or something) for any wheel size from about 20"-24" Cut off the existing dropouts/disc mount and just let the lowers hang down below the axle. I'll end up with a little more rake/offset than ideal, depending on the fork, but IMO it should work great.

Of course, my guy can't even ride a pedal bike yet.









-Walt


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## GrayJay (May 16, 2011)

Walt- I figure your kids pushbike should really have a proper custom waltworks segmented crown fork! 

I've also considered adjustable clamp-on dropouts from several old forks laying around. The early RS SID and very similar configuration early judy forks have the stanchions located a bit ahead of the steer tube to achieve some of the forks rake. The dropouts on these RS forks are cantileverd forward a bit, though not completely ahead of the lowers so a clamp-on replacement dropout definitely would produce more rake than original specification. The castings for the RS lowers are mostly cylindrical however the bottom of the casting has non-round protrusions that would likely need to be cut/ground/machined in order to make the lowers entirely cylindrical. 

Adjustable dropouts would be very easy to implement with early manitou forks as these use cylindrical tubing for the lowers, easy to clamp onto the lowers after the original 26" dropouts are cut away. The design of the original manitou forks had the stanchions in same plane as the steer tube, all rake was achieved by cantilevering the dropout forward of the lowers/stanchions so replacement adjustable dropouts could be fabricated without inducing excessive rake.


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## Birdman (Dec 31, 2003)

Walt said:


> I was thinking of just building some clamp-on dropouts that could slide up and down the fork blades as needed (ie, on an old SID or something) for any wheel size from about 20"-24" Cut off the existing dropouts/disc mount and just let the lowers hang down below the axle. I'll end up with a little more rake/offset than ideal, depending on the fork, but IMO it should work great.


I was thinking of this approach myself. You could do this on a non-disk setup since the rim should always be in the vicinity of the brake posts anyway, regardless of wheel size.

JMJ


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## Walt (Jan 23, 2004)

Or could just build an ISO disc mount into the clamp/dropout on the left side. But yeah, it would be super easy with a v-brake fork.

-Walt


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## Feldybikes (Feb 17, 2004)

Yeah, Walt. 'Cause last time you made an adjustable fork it worked out so well...*

El Hijo de Cuchara Muerte

*calm down internet, this is just a joke.


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## Walt (Jan 23, 2004)

I could just repurpose it. I still have it in the basement!

-Walt


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## PMK (Oct 12, 2004)

*Manitou 4 to 20"*

Found a Manitou 4 on a vintage MTB website.

The most work was spent on removing the expired elasotmers goo from the fork.

Fork outer legs had lower fittings removed. Lower leg tubes were shortened. With careful alignment, and some special tools, the lower axle fittings were aligned and reinstalled.

The upper tubes were not modified.

The plastic pushrod on one side was cut to provide proper axle to crown dimension with the newly added negative spring.

The main spring seat was removed from the pushrod.

A special spring seat was made for the preload adjuster.

A single spring from a vintage Marzocchi Bomber was used.

The spring ends were polished.

Fabricated two bottoming cushions from silicone foam grip material.

The fork brace was modified to clear the V Brake pad hardware.

The crown required a steerer tube swap.

A TapCon, concrete fastener was used to secure the trimmed pushrod at the axle fitting.

Located and replaced seals.

Still running fork boots unless I can find Manitou 3 Dust Seals.

PK


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## TigWorld (Feb 8, 2010)

Nice one! Bonus you did not have to modify the upper tubes. I needed to shorten those on the Manitou (3?) I used because the elastomers were below the stanchions.


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## PMK (Oct 12, 2004)

TigWorld said:


> Nice one! Bonus you did not have to modify the upper tubes. I needed to shorten those on the Manitou (3?) I used because the elastomers were below the stanchions.


Based on your photos, and it was a great tutorial, you modified a Manitou Sport. These were similar to a Manitou 2 with bumpers on the bottom.

So, no I did not need to mod the upper tubes. Lower tubes were obviously modified.

Great idea you had, and done correctly gives good results.

Thanks
PK


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## GrayJay (May 16, 2011)

PMK-
Interesting approach to use the coarse threaded tap-con to secure the push rod after you have cut off the metal machine threads used to retain the stock pushrod.
I am wondering if it might be possible to leave the bottom of the stock pushrod uncut, instead trim the excess length from top of the pushrod and then relocate the stock bottom-out U-clip higher to serve as the seat for the spring to bear on the pushrod in place of the removed top. (it is easy to cut new slots in the pushrod to relocate the U-clip, I did this when I needed to relocate the bottom-out position for fatbike suspension use (26x3.7 tire).


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## PMK (Oct 12, 2004)

GrayJay said:


> PMK-
> Interesting approach to use the coarse threaded tap-con to secure the push rod after you have cut off the metal machine threads used to retain the stock pushrod.
> I am wondering if it might be possible to leave the bottom of the stock pushrod uncut, instead trim the excess length from top of the pushrod and then relocate the stock bottom-out U-clip higher to serve as the seat for the spring to bear on the pushrod in place of the removed top. (it is easy to cut new slots in the pushrod to relocate the U-clip, I did this when I needed to relocate the bottom-out position for fatbike suspension use (26x3.7 tire).


Maybe. Thing is though, I had to cut off the original spring seat also. The new spring seat is the same as the one for the negative spring. The spring seat is shared for both springs.

As for using the oem brass insert in the compression pushrod. Those were a known issue sometimes on the forks back then. They would sometimes spin or pull out of the plastic for no good reason.

I would like to machine a new compression pushrod from aluminum and fit it with a spring seat. Easy to do with a heavy wall tube.

The most upsetting part of this fork is by not cutting the upper tubes, I think this is where the added weight is partially coming from compared to your fork and Tigworlds in the mid 1100g range. I will admit though, this fork is no doubt strong and safe since it retained full overlap of the tubes and has less leverage on account of the shorter lower legs.

PK


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## gpnt (Apr 20, 2009)

Jay
Have you dissembled manitou 4 forks before,just bought a set and they are different inside to earlier models,can't see how to remove the stanctions,wishing the fit shorter stanctions,which I already have.Thanks Graham


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## GrayJay (May 16, 2011)

Service manual for M4 is available at;
suspensionforkparts - Manitou Manuals

I dont think I have worked on a M4 but it appears to be nearly identical to the prior M3 models (which I have worked on).

Are you having trouble removing the stanchion tubes from the crown or removing the lowers from the stanchions?


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## PMK (Oct 12, 2004)

Easy to get apart. On the M4 you need to raise the fork boots or raise the dust seals depending upon how it is configured.

After that, under the boots or seals you will see a circular snap ring that should be easily removed with a dulled screwdriver or being careful not to scratch the fork tube.

Next, remove the two bolts, one per fork leg, at the bottom of the fork near the axle.

With that done, in a perfect world, it will slide apart, with the fork seals, clip and upper bushing remaining on the forks upper leg.

Now the less than perfect, I would assume the orange elastomers have dissolved and are basically gluing the fork together. If I am correct, you will spend a lot of time trying to get it apart without damage. Once apart, use non metal tools and patience to remove the residue from the failed elastomers.

In theory, the elastomers that failed should not be holding the fork together based on the place they were originally located. But for some crazy reason, the failed elastomer goo can flow or moves as you are trying to work on the fork and adds insult to injury.

All the best with it


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## gpnt (Apr 20, 2009)

PMK
Thanks very much,it's so simple but I managed to forget that part,trying to reduce travel and probably replace to stanctions so that the axle to crown is 400mm.I also trying to remove the stanctions from my answer proforx I have both models and i'm guessing the stanctions come out the same way?


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## PMK (Oct 12, 2004)

gpnt said:


> PMK
> Thanks very much,it's so simple but I managed to forget that part,trying to reduce travel and probably replace to stanctions so that the axle to crown is 400mm.I also trying to remove the stanctions from my answer proforx I have both models and i'm guessing the stanctions come out the same way?


I am not sure exactly what the frks length was when completed, but I did not shorten the upper tubes on the M4. Simply shortened the lowers and modified the bottoming system.

A stock M4 when bottomed out does not come close to bottoming against the axle fitting, it bottoms on the C ring and bumper.

In a full size fork, the forks length and travel is set by shuffling the location of the elastomers in relation to the upper tubes guide pressed into the bottom of the upper tube.

The most difficult part in making a kids fork is reassembly alignment. No actually the most difficult part is getting out the goo.


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## melchionda (Sep 25, 2012)

I was going to shorten a Manitou fork but ended up going a different route. If anyone is interested in a box of Manitou fork parts let me know. I have part for three forks with various steerers. Should be enough there to make fork. Send me a message if interested.


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## gpnt (Apr 20, 2009)

Hi
I'd be interested,I'm in the UK so let me know a bit more regarding steerers and models etc,can paypal you if you have what I require.Cheers


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## melchionda (Sep 25, 2012)

Hi, sorry for the delay.. Busy week! I'll dig them out later today and send you the details.


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## gpnt (Apr 20, 2009)

*Manitou forks*

Has anyone here tried converting early manitou forks to oil using later manitou forks with 28.6mm legs you can cut out the legs at the top,later forks have one piece crowns,the only issue I see is the left leg which uses an 8mm allen key at the base which would mean drilling out your manitou 4 forks to allow fitment,anyone familiar with later forks 97-2001 will now just what I mean,axle to crown is virtually the same if you chop out sx tpc model legs which is what I've done but at present using these with an earlier pro c crown,later sx models didn't come with a 1" steerer


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## GrayJay (May 16, 2011)

I've though about it and fiddled with the 97-2001 manitou forks a bit. The design of these later forks changed so that the bottom of the stanchion tube does not hold the lower bushing, instead the bushing material was moved to the inside of the lowers. If you were to simply swap the stanchion to gain damping, there would be no lower bushing.

Trying to use/retrofit the leg from a Manitou 4 EPC fork would probably be easier.


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## ryanpr (May 4, 2017)

Do you still have the box of Manitou fork parts? Im interested in shortening a fork for my small sons 24" bike.


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## melchionda (Sep 25, 2012)

Yes I do... for some reason I'm not getting notifications on replys to my post so if possible email me at [email protected].


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## melchionda (Sep 25, 2012)

I finally got some time to dig these Manitou Fork Parts out of my deep storage. Found some other parts in the box that I couldnt find! Anyway... I'm trying to attached the picture of what I have. All of these forks need a rebuild as the elastomers have decomposed. I took the Sport and the Manitou 3 apart and started cleaning them but never started the fabrication work to shorten them.

The steerer tubes lengths are as follows...
Manitou 3 - 170mm
Manitou 2 - 200mm
Manitou Sport - 155mm (The threaded part starts at 132mm)

I'm looking for $100 for all of these parts plus shipping.


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## melchionda (Sep 25, 2012)

Oops.... I put these forks up on ebay in case no one was interested here and they sold. Sorry to anyone who wanted them and missed out.


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## SpuTTer (Jan 19, 2004)

Hi guys, I picked up a Manitou 4, with plans to convert to 20" as described in other threads.

I had originally planned to cut down the out tubes and the stanchions (maybe use some of GrayJays thoughts to maybe only cut stanchions 2" instead of 3" to increase travel). I was also interested in what PMK had done, and it sounds like I may not have to cut them at all??

Curious to everyones current thoughts on the best strategy to go with, before I cut anything. I have everything taken apart, except it sounds like I may have to hammer out the bushing holders are the end of the stanchions before I cut.

I'm good with going with a metal spring, or making my own elsastomer stack from Amazon as was mentioned by TigWorld.

Does anyone have a picture what it would look like internally with a spring conversion?

Here is what I picked up:







































I'm open to hearing ideas of the best practice recommendations to get this down to 20". I have basic tools, no milling tools or anything, but I may be able to get access to those if really needed.

I know that I need to:

Outer Tubes:
1) Cut dropouts off of the outer tubes
2) Remove tube from cuttoff dropout
3) Cut outer tubes to correct length
4) Press dropouts back onto newly cut outer tubes

Stanchions
1) Cut down 3" (or 2") OR possibly leave uncut (PMK method)

OTHER STUFF
*** It also sounds like I may need to modify some push rods and such. Help me figure this out please, it sounds like I need to cut some of the other parts, etc. Can you use the pictures I provided to help, I tried to take a picture of all the internals.

Thanks!!

I've also got a 26" Rockshox Indy coming and will be doing a 24" mod on that one.


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## SpuTTer (Jan 19, 2004)

My 26" Indy came in for the 24" mod also, will post pics of that soon. That conversion is way easier so I'll probably try that first. I'm hoping some people can still chime in on my Answer Conversion in the post before this.


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## GrayJay (May 16, 2011)

SpuTTer- I am not sure I have much more specific to add to the Manitou conversion beyond the advice already made back in post #12. You can certainly proceed with just trying to shorten the manitou lowers at first, see if it yields adequate suspension travel. If not, then you can start modifying the stanchions and the pushrod arrangement. Just setup to use a single spring on one side, it will provide plenty of force for a small kid. You might need to make or source some spring seats to hold the ends of the steel spring. There are so many variations to the manitou forks it would be hard to come up with a 100% certain conversion recipe for your exact fork but if you start fiddling with the parts you have available you should be able to devise something that works.


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## SpuTTer (Jan 19, 2004)

Thanks GrayJay, I'll just start digging in then!

I did most of the Indy conversion last night. I was surprised to find that my sons Giant XTC Jr used 1 1-8" threadless instead of 1", so the 1" steer tube Indy XC isn't the straight across conversion that I was hoping. Looks like a set of headtube reducers plus a 1" threaded headset and I'll be good, for additional cash. Otherwise the conversion went pretty good, I was also surprised to see the A2C on the rigid fork was pretty long, about the same as the 26", so I didn't shorten a full 1" but more like 3/4" or so. Will post pics once I get that finished, I still haven't cut the end pieces off.


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## SpuTTer (Jan 19, 2004)

I successfully shortened the lowers on my Manitou 4 today!

I've moved onto the internals and I have some plans but I wanted to run it by you all. I'd prefer to not cut the stanchions, so I was looking at what PMK did. I can't find any pictures of the internals that you all have modified, so I'm trying to figure it all out by what was written. I have written up a graphic of my internals and what some plans I have are.

It seems that I am all good, without cutting the stanchions, but the A2C appears to be taller than expeted. I assume that this is BECAUSE I didn't cut the stanchions. I believe this can be offset by cutting off the bottom of the plastic push rod, but I'd like clarification. If I cut off the plastic rod, I'd have to use a tapcon/screw like PMK suggested. There was talk of a possible alternative but I wasn't clear on what it was (just cutting off the top spring seat?)

It also sounds like it would be a good idea for me to cut off the top of the pushrod, to allow for a larger spring area (I had to use a small spring, and chop some MCU's to fit it how it is now).

My Answer 4's pushrod has 3 settings already for different forks, so I think I can move it down to the lowest setting and gain travel, any disadvantage to this?

I have effectively 2 of all the stuff I'm messing with, as I'll only be using one side of the fork, so I have some room to play, but wanted to figure it out before I cut too much.

Thank you guys!

Attached is a picture of what my current state is, with inline questions.


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## SpuTTer (Jan 19, 2004)

I ended up using the bumper on one side for the one I was missing on my side. Cutting down the top seat did seem to lower my A2C but my spring stack wasn't long enough to not have a bit of play in the rod, so I decided to go ahead and just cut the stanchoins. I had about 3/4" of play so I cut 1" from the tubes. The bushing holders popped off with some force and seemed to be expoxied. I wasn't sure what they used so I used blue locktite for now, I'm hoping that's ok but otherwise I could use JB Weld or something. Putting it all back together now for more testing.


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## SpuTTer (Jan 19, 2004)

A2C is still off. Looking at it I need to either:

1) Add more bumpers to the inside of the tubes to shorten that length (will also shorten travel)

2) Cut the compression rod end (will force me to secure using tapcon or screw, etc etc).

3) It also occurred to me that I only shorteneed the stanchions by 1", so I will shorten them by an additional 1", which seems like will lower the A2C by 1". It looks like this will still give enough clearance for a tire, etc, and is the easiest solution.

Any thoughts? I'm going to go with #3 right now. #2 is interesting in that it seems like that extra space at the bottom of the rod is unnecessary anyhow, but I'd rather not lose the threaded piece at the bottom. Another option would be to cut off the top spring seat bits, and cut another slot into the rod, effectively shortening it, but keeping the threads at the bottom. I already have a spare "slide washer" from the other side, so this should work out pretty well. I'm going to simply shorten the stanchions first, and I could play with the rod at a later time if I wanted to mess around with getting more space.

It also seems that I could lose a little more A2C by using a smaller bottom out spacer on the rod. I could conversely add more A2C, but gain more travel, by using a smaller top out spacer it seems. Fun stuff.


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## autoduel (Feb 2, 2004)

I just converted a manitou 4 to 20" and the axle to crown is 14.5"extended and 12" compressed. It had englund air cartridges, so I just cut down the shaft and drilled and re-tapped the end. I did not have to shorten the stancions and the crown drops 1/4" below the fork brace when bottomed out. I added a 1/2" spacer, which in hindsight I could have left out since I forgot to add the bottom out o-ring which raised it another 1/4". I'm running 2.8 tires so I wanted to make sure the crown doesn't bottom out on the tire. But now it's riveted in place with the dropouts so the A2C is fixed unless I reduce the 60mm travel. The stock steel unicrown fork had a 13" A2C measurement.


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## PMK (Oct 12, 2004)

I got a message that I just noticed. Sorry for the late reply.

I did not shorten the stanchions, only the outers. It was beyond super important to ensure pretty exact alignment.

I did shorten the plastic rod. The bottom end was cut to provide proper A2C I wanted. At full compression the tire does not hit the crown. The fork has 60 or 65 mm travel, I forget.


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## PMK (Oct 12, 2004)

Went back and had a look to refresh my memory. The reason on later forks you do not need to cut the stanchions is how the fork was designed originally. The original desin had elastomers above the push rod, the early forks had tne main eladtomers below.

With uncut stanchions, as I posted long ago, I used a portion of a silicone handgrip as a bottoming cushion. The longer stanchion engages the bottoming cushion where the lower end of the stanchion, compresses the silicone against the axle fitting.

As mentioned, by trimming the plastic pushro at the top, this allowed the spring to perch there, the opposite under side of the spring perch, becam a spring perch for a negative top out spring. 

Pretty certain the travel limiting clip was not used at all.


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