On Fri, 2011-10-14 at 10:32 -0500, Tim McNamara wrote: > On Oct 14, 2011, at 1:49 AM, Rex Kerr wrote: > > > didn't solve my problem with the Al fenders moving from side to side and > > rubbing on the tire during climbs > > I can't think of any mechanism that would cause the rear fender to move when > climbing, unless you're getting a huge amount of frame flex. I have seen > situations where the front fender hits the tire due to fork flex, usually > right at the front end of the fender. > > My hunch is that this is occurring when you climb standing. > > If it's the rear wheel, I think what was happening is that your fender is too > close to the tire (there should be 8-10 mm clearance from the tire at its > closest point) and that as the wheel flexes while you climb the tire rubs.. > The point of contact is probably on the left (non-drive side) near the brake > bridge. Rear wheels flex is a slight potato chip shape as we climb standing; > we rock the bike which introduces side loads and the pedaling torque on the > drive side spoke tightens the trailing spoke and slackens the leading spoke, > causing the rim to move. This can cause the rim to hit the brake pad, > usually the one on the left, and a fender if the fender is too close.. This > is less likely to happen with a tight wheel (but a tight wheel is more likely > to crack the rim around the spoke holes, since rim design has been > drastically dumbed down in the past 15 years; a tight rear wheel may make a > bike less likely to shimmy, as well). > > Back in my racing days on climbs you'd hear this "vrrrt vrrrt vrrrt" noise as > the peloton climbed from rims hitting brake pads due to wheel flex. The > became more prevalent after the introduction of dual pivot brakes which need > to have the pads set close to the rim. Pro cyclists will sometimes reach > back and release the rear brake when doing long climbs to prevent this. > Campy came out with a dial pivot front/single pivot rear brake setup a few > years back which I think was intended to prevent this problem.
I'll bet you're right. It can happen in front, too, perhaps from fork flex. -- You received this message because you are subscribed to the Google Groups "RBW Owners Bunch" group. To post to this group, send email to rbw-owners-bunch@googlegroups.com. To unsubscribe from this group, send email to rbw-owners-bunch+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/rbw-owners-bunch?hl=en.
