On Oct 14, 2011, at 10:42 AM, Steve Palincsar wrote: > 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.
Yep, I get some front fender rub on one of my bikes when climbing standing. There's just not enough clearance under the fork and the front brake, so one edge of the fender is about 2 mm from the tire. The fork will flex enough when I climb or ride out of the saddle to rub just a bit. At least I am assuming it is 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.
