# Increasing SR Suntour 40mm travel fork to 60mm



## stom_m3 (Jun 28, 2011)

I found a relatively simple way of increasing the 40mm travel on the SR Suntour fork. The SR fork is a very simple spring only fork. Of the two legs, the left leg is an empty tube and the right leg has the spring and preload adjuster. Remove the pre load adjuster on the right leg (do nothing with the left as it is not bolted in any way). You may need to use pliers/channel locks to unscrew the adjuster. Once you unscrew the preload adjuster push your fork legs up to present the spring. Remove the spring.










Next remove the 10mm nut on the bottom of the fork leg. The fork legs can now be removed. You will notice that there is a ~1.5" rubber piece on the bottom of the fork. The distance from the top of the rubber bumper to the bottom of the stanchion is what determines the amount of travel.










Use your fingers to unscrew the nut below the rubber piece and remove the rubber bumper.










You can cut the rubber bumper down but I wanted to make sure I wasn't over looking something so I simply made an make shift bumper out of a old rubber hoses and plugs that I had laying around. I made the new bumper about 20mm smaller so the fork should now have around 60mm of travel. Here is a pic of the rubber bumper I made. It's specifically stepped to function progressively (me overthinking).










Notice the new distance from the top of the new rubber bumper to the bottom of the stanchion. This is the new amount of travel










Reverse assemble the fork and have your kid enjoy the new travel.

A couple of observations;
1. The air pressure starts to play more into the ability to compress the fork with the added travel. I'll probably drill air holes in the bottom of the fork to allow it to compress easier.
2. Depending on the outcome of observation 1, I may look for a lighter spring. The current spring is around 60 lbs/in. I may look for a lighter 40 lbs/in. spring.

Hope this helps anyone who likes to tinker. The conversion is very simple and takes about 20 minutes.


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## IAmHolland (Jul 8, 2010)

Looking into this as well. There's no nut at the bottom of the fork leg, just some exposed thread. I tried hitting on it with a hammer, while pulling down on the fork legs, it's not budging. I'm stuck there for now.

I noticed the white spacer/reducer on the spring is up in your picture. Mine was down at the bottom. I'm not sure if it's supposed to sit on anything.


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## William_Cannon (May 5, 2009)

Let me know if you find a new spring and how well that works.


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## Cinq (Jan 2, 2003)

Very interesting! The Hot Rock 20 of my son also has a Suntour fork that matches the description. I will have a look into this. Looking at the weight of my son, he will certainly benefit from a less stiff spring, so I am curious if anybody has already tried that.

Kind regards,

Clemens


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## IAmHolland (Jul 8, 2010)

Just following up on this, my daughter's fork was a 6mm bolt through. That is there is no nut at the bottom, but you need a 6mm socket with a long extension or a long 6mm hex handle. Unscrew it from inside the stanchion where the spring sits. The bolt, goes through the bottom of the fork sleeve, there is no nut. The sleeve is threaded.

The white part also goes down at the bottom and not the top. It sits on the bolt head, and gives it some relieve instead of metal to metal contact.

I haven't found a lighter spring, but haven't looked. The daughter hasn't ridden it yet, but she can get down to the bump stops before the mod. I'll see where it goes now.

I cut off about 30mm. I can always restack the rubber spacer after the cut to get back to original height or cut off another section if I need see contact.


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## jh_on_the_cape (Jan 12, 2004)

Clipless pedals? Wow. The fork on my sons trek mt60 is a suntour but has stanchion boots and when I lift them up I just see spring no sliders or stanchions. It's a couple years old.


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## IAmHolland (Jul 8, 2010)

lol, i never noticed the clipless. Where do you get shoes that small?

You don't lift the stanchion boots, you remove the rightmost top cap (imagine sitting on the bike, the stanchion on the right). Removing the cap allows removal of the spring. From there, you either remove the bolt inside the fork, or the nut at the bottom of the fork.


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## SRvancouver13 (Aug 25, 2011)

Hello All,
SR Suntour does have lighter springs available depending on the fork model. Feel free to contact us and we can verify if we do or not.

Just to let the DIY'er and others know that the rebound rubber that has been tampered with here helps control the top out and rebounding effects of the fork. Also I would not recommend drilling any additional holes into the lower casting. 

Best,
Nick


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## IAmHolland (Jul 8, 2010)

Do you sell rebound rubbers to allow for more travel? The website lists 63 (50) (30), is that for 26" fork, 24" fork, and 20 inch fork? Or are those numbers indicating travel options regardless of fork size? I think I'm around 30mm.


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## SRvancouver13 (Aug 25, 2011)

Hello,
You are correct.The travel is limited to the size of the fork for this series of bicycle so the 26" has 63mm, 24"-50mm and 20" 30mm.

If you would like to replace the rebound rubber that you cut feel free to give us a call.

Cheers,
Nick


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## jh_on_the_cape (Jan 12, 2004)

IAmHolland said:


> lol, i never noticed the clipless. Where do you get shoes that small?
> 
> You don't lift the stanchion boots, you remove the rightmost top cap (imagine sitting on the bike, the stanchion on the right). Removing the cap allows removal of the spring. From there, you either remove the bolt inside the fork, or the nut at the bottom of the fork.


I think the fork on my son's bike is different. It's a black Trek MT60. To the guy from Suntour, can I get softer springs for this fork, too? It does not have stanchions like a regular fork. When I lift the boots, the springs are right there with some damper inside. Like a coilover shock on a car.

This is the bike, I just found this image on the web, but it's the same model


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## IAmHolland (Jul 8, 2010)

Yeah, yours is the M3000, mine is the M2025.


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## krud (Jul 18, 2008)

SRvancouver13 said:


> Hello All,
> SR Suntour does have lighter springs available depending on the fork model. Feel free to contact us and we can verify if we do or not.
> 
> Just to let the DIY'er and others know that the rebound rubber that has been tampered with here helps control the top out and rebounding effects of the fork. Also I would not recommend drilling any additional holes into the lower casting.
> ...


 Can you give us a rundown on the differences between the XCT and XCR 24" model forks? It seems most 24" bikes come with the XCT which is extremely stiff and heavy (I have a hard time compressing the one on my sons Specialized Hotrock A1 FS).

Is the new 2012 XCR LO Air a lighter higher performance shock? And where can it be purchased?

I know alot of these bikes may be used on road and the suspension seams to be more of a novelty item, but some of us actually take our kids off road and would like the benefit of a higher quality, lighter suspension fork. Thanks for your help.


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## SRvancouver13 (Aug 25, 2011)

The XCT model fork will use a steel steerer. crown and stanchions in a 28mm platform. In most cases it has a single coil and aluminum lower castings. We do offer it aftermarket with a mechanical lock out.

The XCR model fork will use a steel steerer, crown and high polish stanchions in a 28mm platform. The crown does have a larger stance to it by 10mm giving the rider more stability. It has a single coil spring and Magnesium lower castings giving it a lighter weight. 

Cost between these forks is only $20 retail but the XCR is a much higher level performing fork do to the quality of parts used in manufacturing and overall tolerances. 

As for the XCR with Air, that fork is going to be available at the first of the year. It will have a aluminum upper assembly ( steerer, crown, stanchions). It will utilize an air cartridge similar to the Raidon series and have a hydraulic lock out. This is no doubt the best fork we make in the 24" catergory and I believe has a target weight of 4lbs.

Hope some of this is helpful.
Nick


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## krud (Jul 18, 2008)

Nick, Thanks very helpful info. Looks like the new Air XCR is what I will be getting for my son when it becomes available.


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## stom_m3 (Jun 28, 2011)

IAmHolland said:


> lol, i never noticed the clipless. Where do you get shoes that small?


Not to derail my own thread but you can buy clipless shoes from Fly or THE (Toby Henderson Enterprises). The smallest size they make is a 13. My son started using clipless just before turning 5. I told him he could use them once he turned intermediate in BMX racing. It was movtivational because he continued to win his next 3 races to bump him up.

Nick @ SR - Thank you for making yourself available on these forums. A support that is rare to find and always welcome. I've sent you a PM offline. Thanks.


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## stom_m3 (Jun 28, 2011)

Thought I would update everyone on my quick fix from the first post. I'm still looking for a legit air/oil solution. The only 2 air/oil solutions somewhat available right now are a $720 White Brothers or a $200ish Spinner Air (if Demo9 can make it happen). In the mean time, I'm stuck trying to make this Suntour XCT for work.

In my original post, I thought removing the bottom bumper provided an extra 20mm of travel. It doesn't. Removing the bottom bumper only gives you an additional 10mm of travel. So it increases travel from 40mm to 50mm.

There's an additional 3/4" piece of rubber on the top of the guide rod which I didn't originally take out and review. The purpose of the rubber is to prevent the fork from topping out and making a metal on metal "clack". I removed 5/8" of the rubber and it gave me the full amount in additional travel. The fork crown to axle is now 15mm taller but with the upside of more travel. I also verified that the plastic stanchion guides still operated well and they did.

Now the issue is the stiffer than stiff spring. With my full body weight of 160lbs, I was able to compress the stock spring 1.25". Basic calculating, it would take 256lbs static weight to compress the fork 2" or 336lbs to compress to 2.6" of travel! Far too much for a 6 or 7 year old kid to be able to use the full travel. Maybe there are some superhuman kids out there.

I than realized my wife's old '01 Stumpjumper had a Rockshox Judy SL coil fork. I unscrewed the non-damped leg and what do you know, a coil that looks like it will work as a perfect replacement. The new coil was slightly longer but a whole softer. With the new coil, my full weight compresses the shock all the way down the 2.6" of travel. I would estimate that 140ish pounds could go through the complete travel. A much more realistic load if you ask me. My son rode the bike and noticed the additional compliance instantly.

If other's would like to look into this modification, ebay has spring kits available for the Rockshox Judy SL. There are multiple versions out there so be cognizant of which one you buy. I can provide more specifics if necessary. The one that I put in was the standard red spring. I also used the spring spacer on the bottom from the Judy fork. Surprisingly, the static sag with my son is the same with the old and new spring. I still have the preload adjuster fully open so if needed I can add more preload to the spring. We'll go for a ride this weekend and see how it performs. I'm sure he will be much happier. The next thing to overcome is the stiction on the fork tubes. Don't think I will be able to fix that one but I'll try.

The bottom spring is the stock spring and the top spring is the Judy SL. The rubber piece at the right is the piece that I cut down to extend the travel.









Here's my wife's bike (read donor of the spring)









Close up of the Judy SL









After picture showing with increased travel and higher crown to axle height.









Picture of the coil in the fork.


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## stom_m3 (Jun 28, 2011)

UPDATE: Went for a 7 mile ride this past weekend and the new spring worked awesome for his weight. I could actually see the fork working over the rough stuff. It was nice to see. Unfortunately the fork still has a lot of stichion and small bump sensitivity is non-existent. I used Manitou fork seal grease on the plastic guides but the viscosity is too thin and wipes away too quickly. I'm looking for recommendations on thicker grease that can work with plastic to metal interfaces. Any recommendations would be appreciated.


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## IAmHolland (Jul 8, 2010)

I'm not sure what Manitou fork seal grease is made of or it's viscosity, but you can try dielectric grease from the auto parts stores. It's 100% silicon. You can also try "Superlube". I've only used that on cars and re-packing bearings though. Superlube is thicker than dielectric grease.

Congrats on getting the fork to work well.


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## stom_m3 (Jun 28, 2011)

Here's a quick video showing the action of the fork. I replaced the Manitou Prep M grease with a Silkolene Pro RG2 grease. It's a lithium based, NLGI 2 rated grease. The action is smoother than previous but I'll have to see how it performs after a ride. Since the fork is so simple to take apart (held together with 1 bolt), I don't mind cleaning and re-lubing after the ride.

Testing Front Suspension - YouTube

And I know, I forgot to put his helmet on for the video...

I'll have to take another video of him doing a rough downhill section for a better look. The spring rate seems to be ideal for his weight. I still can add preload to the spring if needed.


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## bigstudent (Jan 14, 2011)

stom_m3, i would like to follow your mod, could you let me know what spring exactly I need to buy.

Also how heavy is your boy pls? Thanks


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## stom_m3 (Jun 28, 2011)

bigstudent said:


> stom_m3, i would like to follow your mod, could you let me know what spring exactly I need to buy.
> 
> Also how heavy is your boy pls? Thanks


My son is ~56lbs. The fork spring is from a Rock Shox Judy SL 2001. I've looked for spring kits and they range from $11 - 20 but most don't say a specific year. The medium spring is red. I found someone selling a 2001 Judy SL on ebay for $10. That might be your best bet. Sorry couldn't provide you better links. Most no longer stock parts this old. The good thing is that the springs are relatively cheap.

RockShox Judy SL Fork 2001 Red Rock Shox Vintage Suspension MTB Not SRAM 1 1/8" | eBay


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## bigstudent (Jan 14, 2011)

Thanks stom_m3, my son is almost same weight, so should hopefully work well for him.
Your video shows noticeable improvment, I think.

I just need to find the spring, hopefully somewhere in UK.

Thanks


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## naiku (Apr 17, 2009)

I might need to find a lighter spring for my sons bike, picked him up a used 2011 Trek MT60, and wow is the fork stiff. As far as I can tell its much the same fork, Trek describes it as a "Dialed SR Suntour 40mm" 

I weight 200lb and had to really push down on the handlebars to get the fork to compress, no way is my son going to be able to get any amount of travel out of it with it currently configured.


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## IAmHolland (Jul 8, 2010)

Take it apart. My daughter's compresses easily, but it's only 35mm and IMO somewhat useless at that range. I haven't done the range extending mods fully. There are a number of bumpers in it, depending on which SR Suntour model you have. I have the M2025 on my daughter's bike and the internals are a bit different than OPs.


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## bigstudent (Jan 14, 2011)

stom_m3, how did you remove the preload dial?
I can't see any obvious way to do it. Sorry seams very basic, but I can't seam to get to the spring.

Thanks


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## stom_m3 (Jun 28, 2011)

bigstudent said:


> stom_m3, how did you remove the preload dial?
> I can't see any obvious way to do it. Sorry seams very basic, but I can't seam to get to the spring.
> 
> Thanks


The preload dial unscrews. Simply turn it counter clockwise.


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## bigstudent (Jan 14, 2011)

Thanks stom_m3, I have manged to open it up, swap the spring and cut the bottom out bumper.
I am getting about 51mm of travel.

But I think I got the wrong "firmnes" spring, so just bought another one.

Many thanks with help for the mod, I am sure it will be worthwhile effort.


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## stom_m3 (Jun 28, 2011)

bigstudent said:


> Thanks stom_m3, I have manged to open it up, swap the spring and cut the bottom out bumper.
> I am getting about 51mm of travel.
> 
> But I think I got the wrong "firmnes" spring, so just bought another one.
> ...


Did you also cut the Top Out Bumper? There are 2 bumpers, a Top Out and Bottom Out bumper. The Top Out bumper is on the top of the bolt. The TO bumper is 19mm long. I removed it and left 5mm. The 5mm was enough to stop the metal on metal clack on top out. This will give you an additional 14mm of travel to get to 65mm overall. Be aware that cutting the TO bumper will also increase your axle to crown height by whatever you remove.

I think you will find this mod worth while. I do find that the fork needs to be lubed with grease after 2 rides to keep stiction to a minimum. Good thing the fork is easy to disassemble.

Where did you find the springs? Possibly you can post where you bought the spring so other's can do the same if they want to do this mod.


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## bigstudent (Jan 14, 2011)

No I didn't cut the other bumper out yet, I'll have a look at it tomorrow. Thanks for the tip.

I have got the spring of eBay, there are few seller that have them.

Thanks


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## Vampir (Mar 15, 2012)

Thanks to this thread inspiring me, I've been tinkering with my daughter's XCT Jr. fork. My starting point was:

36mm travel
151 lbs to bottom out

That is mind blowingly oversprung for a 53 lb little girl. The engineer that thought up that spring rate should find another job. No wonder she was getting almost no action out of the fork.

I ordered a spring set for a 1995-1998 Rock Shox Judy XC, SL, DH. This is the "blue" version that is rated for riders between 130-175 lbs (soft). I figured this would be the right size as I would only be using one of the two springs. BEWARE! Unbeknownst to me, this spring is 1.5" shorter than the stock spring. I had to put in a metal spacer to make up for that difference. I did not shorten the bumpers yet. New measurements:

36mm travel
71 lbs to bottom out

This is a huge difference in the spring rate and is visually noticeable.

My next part of the project is to increase the spring travel and make it more progressive. Stay tuned.


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## Vampir (Mar 15, 2012)

I replaced the metal spacer that I described above with a 1.5" stack of modified skateboard truck elastomers and was able to make the spring rate more progressive and add more travel. Final numbers:

50mm travel
110 lbs to bottom out

I think I'll leave it at that for tonight. We'll head out for a ride tomorrow around the neighborhood to shake out any issues.


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## stom_m3 (Jun 28, 2011)

Vampir said:


> I replaced the metal spacer that I described above with a 1.5" stack of modified skateboard truck elastomers and was able to make the spring rate more progressive and add more travel. Final numbers:
> 
> 50mm travel
> 110 lbs to bottom out
> ...


Vampir - Very cool. Glad to hear someone else having luck.

What are you doing for the stichion issues. Right now I find myself greasing his fork before any decent ride to ensure the stichion is held to a minimum. Essentially, the fork has a built in, non-adjustable threshhold lockout. Unfortunately it's because it's a junk fork.


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## Vampir (Mar 15, 2012)

No stiction problem yet, but she's only got a couple of hours on it since the rebuild. We'll see how it goes this week. We have plans to be out on the trails a lot this week.


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## Vampir (Mar 15, 2012)

Update: I took a week off from work and we spent it camping, swimming, and biking. The shock works so much better than it did before. She can really tell a difference and it made her a lot more comfortable on some of the rockier trails.

We continue to have no problems with stiction. In just thinking about it, could it be that the grease itself is causing the stiction? I very lightly greased the spring in her bike and have had no issues at all. The only problem that I've run into has been that I need to build in a little more preload.

At this point though, I'm thinking a bigger deal for her is to lighten the bike. Seat, post, bars, stem, wheels, and tires are all boat anchors.


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## ktoom640 (Aug 17, 2010)

*Help finding 20 inch susp mtb fork*



SRvancouver13 said:


> The XCT model fork will use a steel steerer. crown and stanchions in a 28mm platform. In most cases it has a single coil and aluminum lower castings. We do offer it aftermarket with a mechanical lock out.
> 
> The XCR model fork will use a steel steerer, crown and high polish stanchions in a 28mm platform. The crown does have a larger stance to it by 10mm giving the rider more stability. It has a single coil spring and Magnesium lower castings giving it a lighter weight.
> 
> ...


Hey Nick,

I am searching for a quality fork to replace the stock fork on my son's Gary Fisher Precaliber 20" mtb. I can't find any reference to it on the Suntour website (or anywhere else on the web).

Please help.

Thanks

Jeff Young
London, ON


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## thesmokingman (Jan 17, 2009)

Vampir said:


> I ordered a spring set for a 1995-1998 Rock Shox Judy XC, SL, DH. This is the "blue" version that is rated for riders between 130-175 lbs (soft). I figured this would be the right size as I would only be using one of the two springs. BEWARE! Unbeknownst to me, this spring is 1.5" shorter than the stock spring. I had to put in a metal spacer to make up for that difference.





Vampir said:


> I replaced the metal spacer that I described above with a 1.5" stack of modified skateboard truck elastomers and was able to make the spring rate more progressive and add more travel. Final numbers:
> 
> 50mm travel
> 110 lbs to bottom out
> ...


Since reading this post, I've been looking for a urethane or elastomer to use as a spacer. That's when I came across the huge range of rods for sale from Amazon. I'm going to get a poly urethane rod, 7/8" OD and around 80A durometer, maybe less around 60A for 11-16 bucks. The harder durometer the cheaper it is. I'm gonna measure again before ordering. Search for rod in industrial.

*Gonna edit this to show my finding that 7/8 is too large a dia for the fork spring hole. The rod from Amazon is just a hair larger so you can either go with 3/4 or shave it down. Btw, a dremel with a drum sander makes short work of the issue.


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## mitzikatzi (Sep 9, 2008)

thesmokingman said:


> Since reading this post, I've been looking for a urethane or elastomer to use as a spacer. That's when I came across the huge range of rods for sale from Amazon. I'm going to get a poly urethane rod, 7/8" OD and around 80A durometer, maybe less around 60A for 11-16 bucks. The harder durometer the cheaper it is. I'm gonna measure again before ordering. Search for rod in industrial.


Like this?

Polyurethane Rod, 60A Durometer, ASTM D-624, Amber


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## thesmokingman (Jan 17, 2009)

Yea that's the rod. I ended up getting a softer durometer, softer than skateboard truck bushings.


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## Vampir (Mar 15, 2012)

Thank you for the elastomer information. That was perfect. The skate truck rings are a little on the hard side (even the soft ones).


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## thesmokingman (Jan 17, 2009)

Vampir said:


> Thank you for the elastomer information. That was perfect. The skate truck rings are a little on the hard side (even the soft ones).


True. I looked at some of the truck bushings and they are all 80A, and that's the soft ones. I ended up swapping the 60A for 40A, going for more squish.










Wee, eta two days.

Your Amazon.com order of "Polyurethane Rod, 40A Duro..." has shipped!

Amazon.com: PUR (Polyurethane) Round Rod, Opaque Amber, Standard Tolerance, ASTM D624, 7/8" Diameter, 6" Length: Industrial & Scientific


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## thesmokingman (Jan 17, 2009)

Just got my 40A urethane rod and I already cut it up. I chose to cut it a wee bit longer than the stock spring for a lil preload.

Just cut










Ready for install










*new host for pics


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## Vampir (Mar 15, 2012)

What did you wrap the end of that with in the last photo? I am very interested in your results.


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## thesmokingman (Jan 17, 2009)

Vampir said:


> What did you wrap the end of that with in the last photo? I am very interested in your results.


It's shrink wrap to keep the ends on and conveniently make the spring, urethane, bottom perch one whole piece. Will let you know how it rides. *edit, doh won't fit with bottom perch shrink wrapped. That top screw hole it too tight dammit.


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## thesmokingman (Jan 17, 2009)

This blue spring may be on the "extra" soft side. When I tried it w/o the elastomer, I could easily compress w/o much force. That's why I chose to make the eslatomer a few mm longer for a bit more preload. With things how they are right now, it takes a more acceptable force (to me) to compress. My son can't bottom out the shock but he compress it along it's natural stroke much more easily. It's night and day.

I used some silicone spray for the spring and stanchions, but haven't really looked into stiction much.


*You know, the bump stops on this fork are freaking harsh. I might make use of all this extra rod to re-do the stops in elastomer instead of hard rubber.


**I made new bushings for the top/bottom out with the leftover elastomer. I've still got enough to make a another set with the 2nd spring (anyone need one?). It's working pretty good, the abrupt top out is softer now. I also wiped it down and used superlube and this has really made a difference on the stiction.


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## Vampir (Mar 15, 2012)

thesmokingman said:


> This blue spring may be on the "extra" soft side. When I tried it w/o the elastomer, I could easily compress w/o much force.


Yeah, but you probably don't weight 50 lbs. 

Looks like its time for me to order a rod of that 40a elastomer and finish the job on my daughter's bike.


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## thesmokingman (Jan 17, 2009)

Vampir said:


> Yeah, but you probably don't weight 50 lbs.
> 
> Looks like its time for me to order a rod of that 40a elastomer and finish the job on my daughter's bike.


I ordered the 7/8ths size but that turned out to be a hair too large. You might want to try next size smaller, 3/4. I used a barrel sander on my dremel to make it fit the dia of the fork hole btw.


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## TigWorld (Feb 8, 2010)

Thanks to thesmokingman for the polyurethane rod info. I couldn't get any elastomers soft enough for the 20" Manitou 2 fork I made for my 27kg daughter. Thanks to thesmokingman's info I was able to order some 40A durometer 3/4" rod and make a single elastomer that has transformed this fork for my daughter. :thumbsup:


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## Vampir (Mar 15, 2012)

TigWorld, that was a great link that you included in your post. The drilling out the center of the elastomer is a brilliant idea. That allows the material room to compress. Good stuff.


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## Julius Ramos II (Jun 23, 2013)

good day everyone.. can I customize such rubber bumper? want to reduce my son's xcr stanchion's(travel)?


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## PiroChu (Apr 8, 2004)

SRvancouver13 said:


> ... the rebound rubber that has been tampered with here helps control the top out and rebounding effects of the fork.


I'm interested in doing this mod as well, but could somebody please elaborate further on what Nick/Suntour said about top-out & rebound? (Meaning... When cut short, then... what/how?)

Thanks, 
- PiroChu


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## stom_m3 (Jun 28, 2011)

PiroChu said:


> I'm interested in doing this mod as well, but could somebody please elaborate further on what Nick/Suntour said about top-out & rebound? (Meaning... When cut short, then... what/how?)
> 
> Thanks,
> - PiroChu


Of course, all of the mods mentioned here either with extending travel, changing springs, converting to PE spring is not going to be recommended by Suntour and is also considered "try at your own risk". I've tried contacting Nick about lighter springs and he never got back to me which is why I had to source my own solutions as well as others theirs. It's obvious that there wasn't much engineering done in creating the fork. What do you expect on $350 bikes with forks that probably cost ~$10.

That said, the top and bottom out bumper durometers are very hard and don't provide much softening at either end. The limitations for the bottom out bumper is that the taper of the fork leg and the stanchion bottoming and jamming at the end of the travel. You can only cut so much off the bottom out bumper before this becomes an issue. The top out bumper, outside of cushioning top out, also keeps the stanchion in the proper range of the fork guide bushings. I haven't had an issue with either top or bottom bumper mods but your may have different experiences. As always, try at your own risk.


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## Aikers (Mar 1, 2014)

Hi
I have just done this mod on the forks for my sons Specialized Hot 
Rock 20. I got the elastomer / urethane 60 form Amazon Supply and picked up Kronos springs on eBay. Both of these arrived from the States within 3 days - well impressed!
I replaced the rubber top-out and bottom-out stops with shorter versions cut from the elastomer. 
The forks now have about 60mm of travel, they are now softer and considerably more useable for the bike. 
While the bottom assembly was removed, I polished the legs with T-Cut and then sprayed them with high impact grease. Hopefully the combination of more movement and this light greasing will help to prevent stiction.
The preload adjuster was in pretty tight and I destroyed it in the removal process, but I picked up a new one, with the special plastic tool from Greyville, Suntour's UK importer. Those guys were super helpful and speedy, so I am sure I will use them for future bike part purchases.


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## -Todd- (Jun 13, 2011)

Great read, subscribed!


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## yair (Jul 31, 2014)

Hi Everyone,

Here's my 2 cents. I've just bought a 2011 2nd hand Trek mt 220 for my 7 year old son. The bike has an m2015 suntour front fork. It has no screws/nuts/bolts on the bottom. Only a single (plastic) screw on the top of the right leg of the fork. After opening the screw, the spring is reveled. I've encountered the same problem as others on this thread, namely, the suspension is extremely hard to compress (even for me and I'm 85 kilos). My problem with the answers is that they directed users to replacement parts that are (or once resided) in another fork. In my opinion, all that is needed is to buy a new spring, and not even one that was originally intended for a bike fork. 

So here's what I did. I saw that my spring was 180mm long, 21mm wide (outer diameter) and 4mm thick (the wire itself). I did some research and discovered that (all else equal) if the spring thickness is reduced by a factor of 2 (X) then the force required to compress the spring is reduced by a factor of 16 (X^4). so I decided to buy a new spring with 3mm thickness (3/4 of the original thickness) which should reduce the force required for compress the spring to around 30% of the original which seemed like a good number to me. It's hard to find springs of exact specifications so I bought one that is 19mm wide (instead of 21) and 200mm long (instead of 180). I cut the spring to 180mm (a bit more actually) with a disc grinder and also ground the end I cut so it would be smooth. I inserted the new spring inside the piston, closed the valve and voila - I could compress the entire travel... easy, cheap, and I hope I've helped someone by sharing.


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## stom_m3 (Jun 28, 2011)

Yair - Good information. You may want to include information or a link on where you bought your spring from so others can follow suit if they choose to do so..


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## yair (Jul 31, 2014)

Hi stom,

I bought the replacement spring in a spring shop in Israel called "The kfitzeriya" (which loosely translates to "The spring-shack") located at Hertzel 100 st. in Tel Aviv but I doubt this will help non-Israelis on the forum. I can say that I researched the subject (mainly using Google) and found many workshops (at least in Israel but I assume that similar ones exist everywhere too) that invited me to come over and see if they had something lying around that would fit my needs or I could order one built specifically for my needs (which costs around 100$-200$ so that option was discarded). I also found a shop that didn't manufacture springs itself but only held many springs of different kinds for sale. I placed my bet on the latter option and found a close-enough-match. The cost was around 4$ for the spring I needed and I bought two of that kind (in case I screw up with the cutting/grinding) and a couple of other similar ones in case my calculations were wrong. All in all I spent 17$ on all of the springs.


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## gonzo84 (Aug 11, 2014)

Hi all, just wanted to say after reading this I too did the mod last night to my sons 20" wheel carrera detonate and very impressed with the extra feel, it even feels softer although that might be down to just having a service. 

I took about 20mm from bottom and just over 15mm from the top and overall got nearly 60mm travel. Unfortunatly ive not changed the coil as finding the softer spring that the OP used in uk seems difficult, is there any others I can look out for?

Thanks
Andy


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## yair (Jul 31, 2014)

Hi Andy,

Read my two posts above. You can definitely find a softer spring. All you need to do is exactly that - look for a "spring", don't look for a "spring-that's-intended-for-a-bike's-fork". There's bound to be some industrial area near where you live with some workshops that manufacture springs. Alternatively you can look for a store that sells springs. I gave specifications for the spring that you would need in my posts. I also gave the proportions (spring strength vs. spring-wire-width) for you to calculate exactly what you need in case your situation differs. 

Please feel free to ask for my help in case you choose to pursue this direction, that's the reason why I posted in the first place.

Good luck,
Yair.


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## Mikey41a (Jul 5, 2015)

Fantastic thread. Before I set out to do this I have a 1997 Indy XL freshly rebuilt with a new elastomer kit from suspensionforkparts - Home and then promptly retired in favor of a new fork. If my short term memory serves me today those elastomers were pre-drilled and should fit because the old Indy uses 28mm stanchions. Can you guys think of any reason not to make use of those? Also my daughters fork seems pretty soft and smooth. I'm not sure but it seems either just right or a touch soft. It is off the newest 2015 20" Boys Hotrock (She hated the cheesy girls frame and opted for the blue & white boys version). Maybe the latest forks aren't sprung as stiff ? How about the pre-load coil springs from the Indy ? Thinking of maybe cutting one in half to add to the top of the stack for pre-load/spring rate increase/progressive feel enhancement. Maybe a chunk of elastomer would work better for that ? Opinions ? Advice?


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## GrayJay (May 16, 2011)

Mikey-
Note that indy stachions are 25.4mm (1"). One option you might consider is modifying the Indy fork later for 24" kid use; 
http://forums.mtbr.com/families-riding-kids/suspension-fork-shortening-932945.html

If you do cannibalize the indy elastomers/springs for the SR, just experiment a bit with the springs to get it right. Problem I have found trying to use elastomers on a 20" fork is that it requires a taller stack of elastomers to provide equivalent suspension travel compared to a steel coil spring. There is simply not a lot of height available in a 20" fork to get much travel from elastomers.


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## Mikey41a (Jul 5, 2015)

Sure. I was actually thinking about adding either the preload spring or a short length of elastomer to the top of the stock xct spring after lengthening the travel to increase preload and/or proggressiveness to the feel of the travel. Similar to what the one fellow did in a previous photo (the shrink wrapped stack) on this thread. Maybe using the elastomer to fashion shorter, softer bottom out and top out stops. Which do you think would work better, the elastomer like the one fellow used or the old preload spring ?


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## Mikey41a (Jul 5, 2015)

Uh oh. I have a new "I think too much" issue. The bottom bumper is I believe a friction damper, providing some crude dampening for the fork. Any danger of turning the fork into a pogo stick ? Has any body else experienced a loss of dampening characteristics, either compression or rebound after doing this mod ? I just want to get it right. By the way Gray Jay my Indy fork is beat to heck and not worth salvaging as a kids fork except for innards. I do however have a cherry Manitou Spider that is on my wifes starter bike (98 Trek 950) that has basically been retired to the garage. She was really not hard on it ever.


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