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Old 05-06-11, 02:40 PM
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Originally Posted by qmsdc15 View Post
996, if you change your fork, get a fork that is designed to be a replacement for a suspension fork. You don't want to change the geometry of your bike, unless you know more about bike geometry than the guy who designed your bike.
qmsdc15 is correct; essentially, though, you're just noticing the effect of 'sag.' A sus fork is designed to have a 'normal ride height' with the suspension compressed by your weight on the bike a certain amount; typically, around 20 to 25% of its stated travel. If it didn't, it wouldn't work properly-- it would just be a silly bouncy-device (which is what many of the cheap/toy suspension forks on inexpensive bicycles are, in effect, and why in many cases it's such a good idea to get rid of them!).

So, e.g., a 100 mm fork is meant to ride with about 25 mm 'sag' (give or take); the geometry of the bike (head/seat angle) is (properly) designed around that 'sagged' measurement.

A rigid fork that correctly fits a given bike will therefore be a little shorter (measured axle to crown) than its suspension counterpart (when measured statically). Staying with the 100 mm suspension fork, for example, on a 26"-wheeled bike, these typically have a static (unsagged) axle to crown measure of around 470 mm (give or take); a proper replacement rigid fork will measure roughly 440 to 450 for the same dimension. That preserves the bike's intended geometry, and therefore handling qualities, provided the fork rake is about the same (they usually are).

Last edited by badger1; 05-06-11 at 02:43 PM.
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