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Epic headshake cause?

512 Views 2 Replies 2 Participants Last post by  ro7939
Two bikes both stock:
'07 Spec Stumpy FSR Comp
'08 Spec Epic Carbon Expert

The Epic susp is tuned in tons better than I ever bothered w/ the FSR; Epic sag is spot on, susp action is superlative on my favorite trail which is pretty stressful on the susp.

Anyway, coming downhill on pavement for several blocks after exiting the trail, the FSR was always a breeze to fly w/ no hands up to moderately high speeds. First time on the Epic, just grabbed the bars in time to avoid an embarrasing high-side after letting go of the bars. Lockout in/out no difference.

Is it just the extra mass of the heavier FSR that keeps it planted? I'm a 6-3 heavyweight if that makes a difference. Both times I was standing on the pedals.

There is a very slight (very) front brake drag that I will attempt to cure on the Epic before taking it out tomorrow. Chance of this drag be related?

Again, the Epic susp is tuned probably better than anything I've ever ridden including hundreds of thousands of motorcycle miles. I'm thinking any susp change to cure the hands-free pavement headshake would dramatically decrease trail performance.

Tire PSI same both bikes. (gotcha!)
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Probably different trail values (coming from different head angles or different fork offsets). Less offset/rake = more trail, which typically means more stability (and less nimbleness). You could also see if the FSR headset is tighter, which would damp steering a little and possibly keep the bike straighter. Sometimes people use tight headsets to control speed wobble. I recently added a lot of hands-free stability to my cargo bike by swapping out its fork for the lowest-rake rigid fork I could find (a Kona dirt jump fork).
Before riding my favorite trail for the second time on the Epic I adjusted the front brake & the excess drag is not gone. Headshake is about 70% eliminated.

Thanks for mentioning the bearing tension, which may well be a bit light. I intend to increase the bearing tension just a smigden (or would a "teensy bit" be more appropriate?) & check results Wednesday.

The more I ride MTB the more perfect an activity this appears to be, minor scrapes & all. I love it more each mile. Doesn't hurt to have taken such a huge upgrade step in the bike, from an FSR Stumpy to the Epic. The Epic climbs hill like it's got a motor. It flies so much faster & quicker that I have to relearn how to ride.
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