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So this time last year at Brenin it was definitely obvious there was a knocking noise coming from the rear suspension of my Canyon Nerve XC. So I ignored it for a while. Did the Brighton Big Dog solo, still ignoring it, it wasn't deafening or anything. Stopped riding it for the most part then toward end of year decided time to fix.
I replaced all the bearings and it still made a knocking noise. Tightened rear cassette (oops) and there was less knocking noise. Bought new TFTuned heavy duty shock mount bushings... still a knocking noise.
I've isolated the knocking to the lower shock mount. The top is ok. THe TFTuned bushings are 22mm width, but the frame requires 22.2mm - When I previously bought TFTuned low-friction bushings I enquired about the .2mm and was told it wouldn't be an issue.
I fitted the replacement heavy duty bushings but used old bolts, so when it continued to knock, I thought the bolts were worn (they are fractionally), but the replacement bolts don't make any difference either.
So....
Could the old bolts have worn the new bushings in 5 rides?
Is it normal for some play to be felt with the unfitted bolts slid through the unfitted bushings?
Is it worth worrying about that .2mm? might a pair of.1mm shims help?
Would the missing .2mm mean the steel tube part of the bushing isn't gripped by the frame adequately even with the bolts torqued correctly (ie 24nm) ?
Is the steel tube part of the bushing meant to be gripped by the frame?
(I would guess so)
Would the missing .2mm mean the steel tube part of the bushing isn't gripped by the frame adequately even with the bolts torqued correctly (ie 24nm) ?
There is most likely your answer.
Depending on the frame design, that 0.2mm extra deflection required to adequately clamp the mount, may involve forces the bolts just aren't capable of providing.
A couple shims, or even just a single 0.2mm shim, will most likely solve the problem.
Thanks mc. The only M8 ID 0.2mm thin shim washers I can find online total £14 for a pair after delivery, may as well just get new Fox shock bushings.
Found a pack of RC Model car shims, Kyosho 8x12x0.2mm, on ebay. If they work and last a whole month I'll be happy. If they don't help then it's only £4.50...