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Old February 26th, 2018, 11:40 AM   #1
Ralgha
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Stock Fork Preload

Anybody know what the stock preload is on the front forks? I assume this preload comes from the part number 92152, fork collar that's 100mm long, but the preload isn't 100mm is it? That seems like a lot.

If I want less preload, I'd have to cut that fork collar down shorter, right? Is that what people do, or do they replace that collar with a section of pvc, which, I assume, is easier to cut?
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Old February 26th, 2018, 12:11 PM   #2
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Using replacement PVC piece allows you to restore stock preload in future. You can cut PVC shorter or longer for less or more preload.

Actual pre-load amount is whatever compression amount is needed to get fork-cap fully seated. So place fork-cap on top of spring, then use calipers to measure distance between top of fork and bottom edge of cap that touches fork tops.
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Old February 26th, 2018, 04:53 PM   #3
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rider weight, rider style, and weather temp, all can effect how much preload is needed.
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Old February 26th, 2018, 05:05 PM   #4
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Weather and ambient temps affect how much preload is needed? That's a new one.


I generically shoot for 20% sag when the bike is loaded and adjust in small increments by feel from there. Use a zip tie or preferably an o ring to mark the fork height. Remember to account for stiction in the seals in your measurement; bounce a few times on it and snug down your o ring to the dirt seal. Then get off the bike and lift the front end with a method that unweights the front wheel. Generally speaking, rough roads benefit from a *little* more sag

Remember that preload and spring rate are not the same thing. Adding preload won't give you a stiffer front end, just a similarly squishy front end that rides at a different height.

Also remember that if you don't listen to JacRyan's advice above and take all preload completely out of the spring by using a tiny spacer, taking the fork caps off becomes a little more fun.
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Old February 27th, 2018, 12:09 AM   #5
Ralgha
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Thanks, I know what preload is, just didn't know what the stock setup is. Replacing stock spacers with PVC sounds good!
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Old February 27th, 2018, 11:08 AM   #6
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You probably know, but you can alter the stiffness of the front end by adding or removing oil, within limits. More oil leave less air space, and so the air pressurizes more as the fork compresses.
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