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Let's say I am reading spec for 29er with suspension fork and I would like to calculate replacement parameters for rigid one. Calculation is needed because I don't want to change geometry after replacement -- so the rigid fork should feel (in sense of geometry) as locked in neutral position suspension fork.

How to do the calculation, what parameters are important? Example:

"Custom SR Suntour XCT 29, w/ custom Multi-Circuit Damping, alloy lowers, coil/MCU spring, Hi-Ten 28mm stanchions, 1-1/8" steerer, hydraulic lockout w/ preload adjust, disc mount, 100mm travel"

(text from Specialized Rockhopper 29).

Background 1: I want to do calculations before I buy the bike to avoid situation, that I am buying popular bike but there is no rigid fork replacement (or it is very hard to get).

Background 2: In reality I wanted to buy fitness bike (100% rigid, disc brakes, 700C) and mount wider tires (2"). After some query it appears that all fitness bikes (like Trek 7.2 FX, Cube Hyde, etc) have so little space that you can fit 1.75" tire max (Kross Seto). I found only single bike so far with frame for wider tires (Sulry Ogre), but it is out of reach for me (Poland). So I see no other option as do more expensive replacement -- instead of buying fixed fork bike and replacing tires, buying 29er and replacing fork.

  • This seems all a bit weird - if you want a fitness bike, why do you want 2" tires? Also, why not pick up an old rigid mountain bike (like an 80's or 90's rockhopper) and use 26" wheels and put a 2 inch tire on that, if you want 2 inch tires for some reason? – Batman Mar 10 '15 at 12:47
  • I have seen this calculation done with a hacksaw – PeteH Mar 10 '15 at 13:18
  • @Batman, it is like asking why do you want black bicycle, when white are available. My personal preference is 700C wheels plus 2" tires (I already have 26" bike with 2.35" tires). – greenoldman Mar 10 '15 at 14:12
  • @PeteH Really? Please explain how you measure with a hacksaw? Or how this a hacksaw is a solution to the problem? – paparazzo Mar 11 '15 at 0:25
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If you want a rigid fork for a 29er with shocks just buy a fork for a suspension corrected frame. If the fork is listed for a mountain bike then it is (probably) suspension corrected. I suspect that about any rigid fork that will take a 2" tire will be suspension corrected.

Measuring is not going to do you much good as you can't buy custom lengths (that I am aware of).

Below is a suspension corrected rigid - see the space at the top:
suspension corrected rigid - see the space at the top

For a workout bike I don't get why you need 2" tires? You are going to have trouble finding road 2" tires. There are some rigid mountain bikes (Niner Ross 9 Plus) and also the Salsa Fargo. Another option would be to buy a used mountain bike priced right because of a worn out shock.

  • The tires are no problems, I use semi slicks, and I already found OK tires for me. Back to the question -- so it is safe to buy a bike, and then simply look for this kind of fork? Thank you very much (for the image as well). Fargo has dropbar AFAIR (I will check again). – greenoldman Mar 10 '15 at 14:16
  • Why not? The frame does not know the difference. You use the same headset. Look at Niner - they sell rigid and suspension on the same frames. A nice carbon fork is not cheap but it is sweet. – paparazzo Mar 10 '15 at 14:21

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