1

I have a 2008 Trek 4300 MTB (v-brake version) and am looking to replace the RST 100mm suspension fork with a rigid fork, but am having trouble finding something suitable. I measured the fork length to be roughly 19 3/8" (~492mm). All the rigid forks I've found (Surly 1x1, Sunlite) seem to not quite have the a long enough fork length. I'm hoping someone here might have a suggestions. Thanks.

measurement

3

That is a very big axle to crown number for a 100mm 26" fork. 490s for 26" is more associated with dirt jump/downhill/etc, hence the lack of options you're finding for a mass produced rigid conversion fork. What you'd want if you could get it is something around 465-470mm, which represents what the front end ride height would be with around a quarter of the travel used up statically, which is kind of the baseline rule of thumb that manufacturers go by to figure out what the axle-to-crown is going to be on their rigid conversion forks. Most 100mm 26" forks, say an F100 or Reba, were in the 470-475 range, so most of the rigid conversion forks for that sort of bike are around 445-455. It's all a game of approximations.

There were a few rigid suspension corrected canti post forks in that era that were kind of in the dirt jump/"BigMX" genre, with long, heavy, non-tapered chromoly legs. There was a Redline one in particular I'm thinking about that I'm unable to find numbers on currently, but I wouldn't be surprised if it was longer than everything else. It was very long and heavy.

If you can find a 1x1 canti fork, at 453mm they're on the longer end of what exists for this. That plus a 10mm extender headset lower gets you about where you'd want to be - maybe a little shy if the bike really is designed around a 492mm fork, but it really shouldn't be a big deal riding. Even without the extender it would still be perfectly rideable, but the rider position change would probably come into play more.

| improve this answer | |
  • Thank you. I agree that the measurement seems high, but I repeated it multiple times. Admittedly this measurement is with the preload set all the way up so with no sag. I'll look into the options you provided. The background info is particularly helpful! – BILL BONER Feb 24 at 16:03
1

I replaced the suspension fork on my old mountain bike with a shorter rigid fork, about 25 mm shorter from axle to crown. It noticeably changed the steering geometry. The on-center stability is reduced, making it easier to turn. The quick steering and reduced weight make the bike feel more agile.

It also lowered the bottom bracket, maybe 10 mm. I sometimes hit the ground with the pedals when leaning in a turn. Then I switched to shorter crank arms to prevent that.

| improve this answer | |
  • Thanks for relaying your experience, I appreciate it. – BILL BONER Feb 25 at 0:51
0

Take a look at Somafab. I believe it is a threadless fork, and they have a pretty good selection.

Probably the CRMO MTB 26″ DISC FORK. You could contact them about exact measurements to see if the geometry is compatible. I used a True Temper steel fork as a replacement for a 10 year old carbon fork and the quality is very high. This was on a road bike. I don't have experience with the MTB fork specifically.

| improve this answer | |
  • 1
    A one-line answer could be better - Can you edit info about this kind of fork, and why its a good fit? Do you own one? What's your experiences with it ? – Criggie Feb 24 at 8:12
  • 1
    A quick look at the SOMA Fabrications website shows 22 forks. Which one are you recommending, and why? – DavidW Feb 24 at 15:28

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.