When I am breaking with the front, the fork wobbles a lot.
It seems the breaking pads are stick-slipping with the rim make the fork enter in resonance. I've never seen a fork wobbling like that.
Bike: Focus Mares, carbon, cyclocross
What do you suggest?
by idiophile
8 Comments
Yeah, I’d stop riding that
This can be a few things unfortunately, so begin with whichever you feel is most probable in your case:
1. Loose quick release
2. Contamination of the pads and brake surface can cause inconsistent braking. Sand your pads and rub your brake track with methylated spirits to remove residue.
3. Wobble is coming from headset. Make sure that there is no play.
4. Frame/spacer mounted cantilever brakes with flexible forks can cause a bowing effect under braking. Mounting the straddle from the fork can solve this.
5. Improve brake pads/ angle of brake pads/ install a brake booster. These are all last ditch options if you want to keep your cantilevers if all else fails. Mini v brakes will likely reduce shudder in this case.
Good luck!
Is your wheel true?
I’ve had this issue before with cantilever front brakes, and the solution was using a fork mounted cable stop. As you currently have it the cable stop for the front brakes is up by the headset. The flex of the fork under braking releases cable tension, causing the brake to release, which then allows the fork to flex back applying the brake again. This cycle is what’s causing the judder.
Quite common thing with canrilevers, can be alleviated.
Basically what happen is that the fork will normally flex during braking and in doing so will slightlyincrease the front brake cable tension, then it will oscillate and loop this situation. Setting up the fork and headset so that there is minimal play of course is paramount and then I was told I should “toe” the brake pads, and it means angling them so that their front part touches the rim slightly earlier than the rear part. what I did was tie a thin ziptie around the rear of the pad, brake, undo the pad attachment and redo it again, then remove the ziptie (that acted like a spacer). It works for me and you can find good tutorial on yt (try “cantilever chatter”. I hope it works.
Perfectly common with cyclocross due to cantis. Your pads bite in, the whole system (fork, cable) flexes, in the process of which the pads get pressed more onto the rim, causes the wheel to stop the “resonance” releases the cable tension and the cycle repeats. At least this would be my prime suspect.
Where is your brake cable anchored in the front? Under the bars or the crown fork? If above, this could be even loose headset. Ruling that out, the simplest to start is with the brake pads toe-in, etc – look for instructions for canti brakes.
One of the things I like to do is swap around the spacers “around” the pad. So that each pad is getting less of a swivel. While at that make sure the brake arms are bolted firm onto the fork bosses.
Check if you have headset play first.
There are some good suggestions here, the fork mounted stop is top suggestion, based on my struggles with these issues in the past.
On trick we had at the shop I worked at, when all else failed, we would mismatch brake pads. Shimano on one side, Kool Stop salmon on the other (doesn’t need to be these pads, they just need to have a different compound, so the resonate at a different pressure level). Keep the spare pads, and you switch them when you need new pads.
It seems like this trick works really well for chatter, and vibration in general (so also squealing).
That said, try the easy ones listed above first!