Warning: Do not modify or misapply FOX forks

This FOX announcement comes just in time.

Basically: 1) Unless you’re riding a 32 F29, you should only run 26 inch wheels. 2) Never, ever modify the structure of your fork to accommodate bigger wheels.

Source: Fox Racing Shox

It has come to the attention of FOX Racing Shox that certain individuals and / or entities are modifying FOX forks to accommodate mountain bike wheel sizes other than those having 26 inch nominal diameter. One such modification includes removing material from the lower leg cross bridge in order to fit a 29 inch tire in the fork. Such modification will ultimately separate the lower fork legs at the cross bridge (i.e. the weakened cross bridge will fracture) and may cause bicycle instability and crash that result in SERIOUS INJURY OR DEATH.

NEVER REMOVE MATERIAL from any portion of a FOX fork. USE ONLY 26 INCH WHEELS with FOX 32*, 36 and 40 bicycle suspension forks. Those FOX forks are designed and tested for use ONLY with 26 inch Mountain Bike wheels / tires. Use of FOX forks with any wheel other than 26 inches and/or alteration or modification of any FOX fork will subject the FOX fork to loads and forces it has not been designed or certified to meet and will void all warranties. The FOX 32*, 36 and 40 models meet CEN and ASTM testing standards ONLY when used with 26 inch wheels / tires and are not recommended or approved by FOX Factory, Inc. for use with wheels larger or smaller than 26 inches, either as original equipment or aftermarket.


Proper forks are critical to proper bicycle handling and stability. Improper function or failure of a bicycle fork while riding can cause a bicycle to become uncontrollable and result in a crash. Use of FOX 32*, 36 or 40 forks with wheels larger or smaller than 26 inches, or any other modification, may cause crashes that result in SERIOUS INJURY OR DEATH. Never ride a bicycle that is, or appears to be, fitted with a FOX 32*, 36 or 40 fork that has been modified and / or fitted with any wheel larger or smaller in nominal diameter than 26 inches.


For those of you who want to ride on 29 inch front wheels with suspension, FOX offers the 32 F29 fork designed specifically for 29 inch wheels. The F29 is available in 80mm, 100mm or 120mm travel configurations and is ideal for tall wheel applications. The F29 is the only FOX fork available for use with 29 inch wheels and is clearly labeled “F29” on the right leg. The F29 should be used only with 29 inch wheels. As with all FOX forks, do not modify or misapply, or ride on improperly applied or modified FOX F29 forks.


Do not modify any portion of a FOX fork and do not purchase or use any fork that appears to have been modified. Any FOX 32*, 36 or 40 model fork that appears to accommodate a tire larger than 26 inches in nominal diameter, such as 650b or 29 inch, should be avoided. If any doubt exists as to the originality or proper application of a FOX fork please contact a FOX representative.

Thank you,

FOX Racing Shox

15 replies
  1. Sean says:

    It is sad that our culture is so litigious that Fox Racing Shox needs to issue such warnings. But I agree, there are some idiots and selfish jerks out there who will sue Fox or other fork makers for something not the fork maker’s fault. I would love to see American society get back to personal responsibility, but I don’t expect it to happen. As long as those idiots and jerks exist, these kinds of warnings will be required.

  2. Mr. P says:

    After reading this I feel like riding my bike, I will “crash that results in SERIOUS INJURY OR DEATH.”!!! lol.

    I guess what Fox is saying is that their 20mm through axle interface isn’t strong enough to support the fork. lol. Just joking. Ok, kind of not… :-/

    I agree with the litigious comments above.


  3. Ben says:

    I’ve heard people call it the “IPS” Idiot Protection Service; all the non-idiots have to protect all the idiots (something about keeping the species going or something like that)

  4. nathan says:

    I reckon BCD shouldn’t be selling 40s with the arch cut *and* the Fox logos on them – because it’s abusing the Fox mark, but I don’t think it’s wrong to sell them in general, i.e. without the Fox mark. He’s doing pioneering work that may come to benefit the entire DH scene eventually. For their to be a negative community outcry about his work would be shameful.

  5. Mr. P says:


    A 32mm stanchion XC fork with QR (= no real bottom structure) huckin’ on a 4X course = OK


    A 36mm or 40mm stanchion fork with a bolt on 20mm TA, and a bit of material removed from the arch = potential “SERIOUS INJURY OR DEATH”???


    Fox has made no comment on their sponsored riders riding their 32 series forks well beyond their intention, but will write up this legalized positioning statement on some basic experimentation. At a minimum, Fox is being inconsistent.

    Perhaps I just have problems with the “SERIOUS INJURY OR DEATH”” repeated over and over again.

    I dunno. Do you think that some material removed from the arch (say 10mm) is enough to compromise a bolt-on 20mm axle fork?


  6. leelikesbikes says:

    1) Liability is a huge concern here. FOX has to cover its tail. Ha ha.

    2) A 36 or 40 has enough material in the right places for it to withstand a certain type of riding and provide an extra margin of safety. Remember that all good products are tested way beyond the abilities of mere mortals. Removing material definitely eats into that safety margin — and that’s if you know what you’re doing. I doubt many of us are qualified to decide which material is necessary, and which can go.

    And what happens when you have a strange crash or, more likely, you hit an unseen hole at high speed? (Any of you ever raced DH at Vermont?) Violent things happen to bike parts. I, for one, will leave all of the material where the engineers think it needs to be.

  7. leelikesbikes says:

    Side note:

    I had a stock 1986 1/2 Nissan 4×4. That truck was awesome. Even with street tires, it outperformed my buddies’ heavily modified F350s and Jeeps. Why? I think the Nissan engineers knew what they were doing. Who am I to think I can do better.


    Back in the day, the same buddies and I built a dune buggy. It came with stock VW rear suspension. We were young, and we had access to a machine shop. We built our own suspension way burlier, stiffer and more macho. And it sucked! The beast bounced all over the place, and we kept breaking parts. We soon went back to stock, and that ‘rail railed!!!!!!

  8. Mr. P says:

    After sleeping on it, I realized I am just e-speculating, and arm chair engineering. I’m not one to mod structural changes for the reasons outlined by Fox – so in action I guess I agree with them. I guess the repeated, “SERIOUS INJURY OR DEATH.” got my panties in a wad. 😉


  9. Andrew Hass says:

    if you’ve ever talked to alex about his work you know he knows way more than anybody on the internet does. i’m sure the guys at fox would let him do whatever he wants. everybody else needs to do what fox says… DO NOT RIDE ON MODIFIED OR MISAPPLIED FORKS. until you have the history with bike design that alex has dont make the same decisions as him

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