Pike Coil spring rate when travel is reduced

[TooManyTacos]

I had a Pike Coil U-Turn on my big bike, but got a sick deal on a Dual Air, so the Coil is going on my 100mm travel bike so I can take advantage of the 20mm axle. Does the spring rate or compression change when the travel is wound down from 140mm to 100?

[2wheel_lee]

Yes, as you lower the fork, the coil spring gets stiffer.
See page 6 http://www.sram.com/_media/techdocs/07%20PikeRebaRevelationDomainArgyle.pdf under Coil Spring Tuning.

[TooManyTacos]

Thanks, good to know!

[Chewyeti]

F = KX

F = force of the spring
K = spring coefficient
X = deviation (distance) from natural at rest spring length

so yes... squished spring = more force

[2wheel_lee]

Originally Posted by Chewyeti

F = KX

F = force of the spring
K = spring coefficient
X = deviation (distance) from natural at rest spring length

so yes... squished spring = more force

The U-Turn system does not squish the spring. It is not a preload mechanism.

Instead of using the full length of the spring, the U-Turn adjustment mechanism essentially engages the spring somewhere in the middle, rather than at the ends when the fork is at full height. So because you're compressing a shorter length of the same spring, the spring rate is higher.

[Chewyeti]

oh that makes sense... good to know