# Suspension-corrected rigid forks?



## SpinWheelz (May 3, 2004)

Looking around for a rigid fork for the SS I'm trying to throw together. I see that some forks are described as 'suspension-corrected'? This may be a dumb question, but could someone please enlighten me on exactly what this means?

Cheers.


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## czardonic (Jan 15, 2004)

These have a longer axel to crown height to give a suspension corrected frame the same geometry that it would have with a suspesion fork.

A suspension-corrected fork will raise the front end of a non-suspension corrected frame, thus slackening the angles and slowing the handling.

A non-suspension corrected fork will lower the front end of a suspension corrected frame, thus steepening the angles and making the steering quicker.

If you currently have a suspension fork (or suspension corrected rigid fork) on your frame and you like how it rides, go suspension corrected.


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## DeeEight (Jan 13, 2004)

except not all "suspension corrected" rigid forks are the same, as different companies might have designed them for specific frames or equivalent length suspension forks. I have one that's 17.5" crown race to axle in length for example, and that's about the same length as a 100mm travel fork with 20mm of sag.


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## SpinWheelz (May 3, 2004)

Sounds like a redundant phrase, no? If certain fork manufacturers offer rigid forks in different lengths so that you can best match it to your 80mm, 100mm, 120mm, etc. suspension fork, then what makes suspension-corrected fork different from one that's not suspension-corrected? Or are these fork models with various lengths the same suspension-corrected forks in question?


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## czardonic (Jan 15, 2004)

"Suspension corrected" is mostly and indication that the fork comes with longer axle to crown height(s). Some fork builders tell you the axle to crown height(s) right of the bat, some tell you how many inches of suspension they are designed to compensate for and some just tell you "suspension corrected" and leave you to figure out what that means for their fork.

The bottom line is to measure your current fork (accounting for sag if it is a suspension fork) and then find a rigid fork with a similar axle to crown length.


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## Rockdogger (Jan 28, 2004)

*suspension corrected*

originally frames/forks were designed around an average 410-415mm axle to crown. That corresponed to a 63mm travel fork with sag.

Then sussy forks grew to 80mm travel, so "suspension corrected forks" were designed around a 425mm axle to crown to match.

Sussy forks grew again to 100mm travel and rigid forks were again created around a 435-440 axle to crown to match. These are the same forks used on 29er's from kelly, vicious etc.

Besides the Karate Monkey(468mm), 440mm is about the limit for unicrown rigid forks right now. This is due to fork leg tubing availability.

So you can see there are now 2 suspension corrected lengths. Pick the size that matches your sussy fork and it shouldn't effect the handling.

A longer fork will slow things down, a shorter will speed things up.

If you are building a new ride from scratch, check with frame manufacturer and see what size fork the frame was designed around and get the corresponding rigid fork


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## SpinWheelz (May 3, 2004)

Thanks for that thorough explanation. I am building a ride from the scratch using a 1999 Specialized Stumpjumper frame. Unfortunately their website does not list this bike any longer, but I'm more inclined to go with a ride that has a very steep setup anyway. So I'll look into some of shorter dimensions you stated.

And here all this time I thought 'suspension-corrected' forks were rigid forks with a bit of bounce and flex to them...


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## Rockdogger (Jan 28, 2004)

*stumpjumper*

99 stumpjumper was designed around a 63mm sussy fork.

Try a Surly 1x1 fork. 413mm axle to crown, strong, disc &/or canti mounts and $50 on ebay/classifieds.

Should match the stock handling very well.


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## SpinWheelz (May 3, 2004)

Thanks again, Rockdogger. Brilliant stuff!


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## hu-man (Jan 13, 2004)

Rockdogger said:


> originally frames/forks were designed around an average 410-415mm axle to crown. That corresponed to a 63mm travel fork with sag.
> 
> Then sussy forks grew to 80mm travel, so "suspension corrected forks" were designed around a 425mm axle to crown to match.
> 
> ...


Don't forget to take your tire size into account if you are planning to run a big fat tire up front. I went from a 26 inch wheel/2.1 inch tire with a 80mm sussy fork to a Surly 1x1 and a 2.7 inch DH tire. The FAT tire resulted in a 27 inch wheel diameter, which when combined with the Surly fork - which leans more to a 63mm susprnsion correction - resulted in the same head tube angle as my original set up. I like the handling so that's OK.. If I had gone with a 80mm corrected fork plus the FAT tire, the result would be a slackening of the head tubeangle.


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## Jason Boi (Nov 29, 2006)

*help*

Hey guys,
Need some help here.
I ride a Voodoo Bakka. Currently with a Fox Vanilla RL 140mm on it. Was thinking of a rigid fork for it. What would be a suspension corrected fork with an axle to crown that fits that?

Cheers
Jason


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## monogod (Feb 10, 2006)

Rockdogger said:


> Besides the Karate Monkey(468mm), 440mm is about the limit for unicrown rigid forks right now.


and the niner fork at 490mm.


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## cutthroat (Mar 2, 2004)

Rockdogger said:


> Besides the Karate Monkey(468mm), 440mm is about the limit for unicrown rigid forks right now. This is due to fork leg tubing availability.


 Just about any 29er rigid fork on the market has an average 465-470mm AC length, Salsa, Kona, Vicious, Pace, White Bros, etc. all make forks with this AC length. You can run any of these forks on a 26er if you want the slacker head tube angle it will offer. The "suspension corrected" thing is just too confusing - figure out what AC length your bike's frame geometry was designed around - match that AC number to keep the handling the same as the stock design. Go shorter or longer if you want to quicken the handling or slacken it out. If the frame manufacturer does not tell you what the AC spec is for given frame, then you may have to back into by figuring out what fork was intended for the frame originally then calculating the AC based on the fork spec.


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## gte819s (Aug 13, 2006)

DeeEight said:


> I have one that's 17.5" crown race to axle in length for example, and that's about the same length as a 100mm travel fork with 20mm of sag.


And which one would that be? I have been looking for a 440 disc and the closest i can get is a newer revision P2 with studs only (bikeman)

Or a surly instigator/pugsly at 1440grms and a2c of 447mm.


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## cutthroat (Mar 2, 2004)

Bikeman has three pages of forks with various AC lengths - quite a few in the 440-445 range: http://www.bikemannetwork.com/category.php?code=COMPFKMTNR&p=3&store=1

I'm very happy with my Kona P2


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## tpm7 (May 14, 2007)

Jason Boi said:


> Hey guys,
> Need some help here.
> I ride a Voodoo Bakka. Currently with a Fox Vanilla RL 140mm on it. Was thinking of a rigid fork for it. What would be a suspension corrected fork with an axle to crown that fits that?
> 
> ...


I only know of one fork that is around that length, it's a 465mm long one, available in Aluminum or Rigid. I just got a 425mm Alu one from here for my bike. Check them out, see if the 465mm will work for your bike. http://www.carboncycles.cc/?s=0&t=0&c=43&p=498&

White Bros also has the same fork (as well as many companies, same fork branded differently) http://www.whitebrotherscycling.com/rock.shtml

Salsa makes a 468mm one. http://www.salsacycles.com/forks.html


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## monogod (Feb 10, 2006)

tpm7 said:


> see if the 465mm will work for your bike.


imho the best choice with a 140mm squish would be the niner @ 490mm.


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## Treybiker (Jan 6, 2004)

Here a better and simpler explanation. There is a little give or take depending on who you're talking to.

425 is non susp corrected OR for the old 50-60mm forks
445 is for 80mm
465 is for 100mm, (or 80mm on a 29'er wheel)


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## Doggity (Mar 27, 2007)

Treybiker said:


> Here a better and simpler explanation. There is a little give or take depending on who you're talking to.
> 
> 425 is non susp corrected OR for the old 50-60mm forks
> 445 is for 80mm
> 465 is for 100mm, (or 80mm on a 29'er wheel)


Wish somebody had posted this simple table when I was getting my Salsa Cromoto fork.
It's 425mm, and I placed it on an '01 RM Blizzard, which I believe is 80mm susp. According to this, I shoulda gone 445? Ah, well...it's got to be better than the 393mm Tange fork it replaced! I'm about to go to wider tires, that ought to help.


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## gte819s (Aug 13, 2006)

Yeah it makes no sense to me.  
I did a shotgun survey of 80 mm and 100 mm sus forks and found the common a2c was approx 460 and 480. So factoring in sag for each that would give 445 for an equivalent 80mm and 460mm for a 100mm, just as Trey wrote. Most sources claim a 420ish mm is a replacement for a 80mm fork and 440ish for a 100mm. For the OP I think some 29ers have been stated as acceptable for a 130mm replacement on 26ers but thats at a lower comparable a2c as well. Anyone know why?


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## tpm7 (May 14, 2007)

gte819s said:


> Yeah it makes no sense to me.
> I did a shotgun survey of 80 mm and 100 mm sus forks and found the common a2c was approx 460 and 480. So factoring in sag for each that would give 445 for an equivalent 80mm and 460mm for a 100mm, just as Trey wrote. Most sources claim a 420ish mm is a replacement for a 80mm fork and 440ish for a 100mm. For the OP I think some 29ers have been stated as acceptable for a 130mm replacement on 26ers but thats at a lower comparable a2c as well. Anyone know why?


That's why I was confused with my post earlier, it states a 465 would be a good replacement for 29er or 130mm fork... I went with the 425 for an 80mm fork... it sits lower for sure but I'm not sure if it makes up for sag or not because I already tossed the old fork... Best thing I think to do is measure the sag when you're sitting on your bike and get a rigid to match the same or approximate length and ignore the posted equivalents.


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