SF Cyclotouring

Ride reports and other ramblings from a San Francisco cyclist.

7/25/2008

Frustrated!

Friction Downtube ShiftersMarathon bike-shimmy debugging session tonight. Status: unsuccessful! Things I've tried so far:

Changed to a different front rack, one that mounts at the fork-end eyelets instead of the cantilever brake studs.

Cleaned out and re-greased the headset.

After noticing a wobble in the rear tire due to the bead not seating evenly, I changed to a completely different set of tires.

Lowered the handlebars; raised the handlebars.

Took off the front fender; reinstalled the front fender.

Thinking that the shimmy might be due to some weirdness with the tension in the bar-end shifter cables, I unhooked those and installed down-tube shifters (tangential note: Mavic DT shifters do NOT index with Shimano 9spd). When rolling the bike around, the steering is much looser/floppier since the stiff SIS cables are absent, but the no-hands riding shimmy persists.

Along the same lines, I unhooked the rear brake cable and rode down my street, but I don't think that helped -- I need to retest. My brain's going a bit fuzzy @ 12:45am.


The only other thing I can think of is to get the head tube faced.

Any other suggestions?

2 Comments:

Blogger blackmountaincycles said...

I suppose a larger diameter or thicker walled tube is out of the question ;-) This might be grasping at straws, but perhaps spraying some of that expanding foam into the top tube and down tube? Remove the front rack altogether? Maybe try something like this a Jandd frame bag that fits inside the front triangle at the head tube?

8:08 AM  
Anonymous brian said...

Is it possible that it's just the geometry of the bike? I've mostly ignored much of the trail discussions on the BOB and KOG lists, but my impression was that the P/R had apparently hit some sort of geometric sweet spot....

11:04 AM  

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