Hello,

I have a Trek Madone 4.5 and the brake constantly shift back and forth and rub on the wheel. I have straightened them and tightened them down, but they start to slide. I can get them to stay put if I crank down on the screw but am afraid of breaking the carbon frame. Any suggestions?

Example: I was cleaning my bike, hopped on it for a quick ride around the block and noticed I was stopping as soon as a stopped pedaling. I hopped off and looked at my brake pads only the find the front and back brake housing units had shifted over so one brake pad was constantly rubbing the wheel.

Broady

You might find good advice on the Bicycle Mechanics forum.

Meanwhile, is your brake cable pulling or pushing on the caliper because it is too short OR too long, respectively? Is the knurled washer, that keeps the caliper straight, missing? Are you adjusting the caliper position as recommended by the manufacturer, not just "ham fisting" it. Which brake, front or back?

Are you saying the caliper won't stay centered, or the fixing bolt going through the frame is coming loose? If they just won't stay centered then try lubricating the contact points where the springs touch the caliper. If the fixing bolt is coming loose then, I don't know maybe put some locktite on it.

The first step is to determine if the entire brake is moving with respect to the frame, or it's something the brake. So, remove the wheel and twist the caliper to see how much force is needed to move it on the pivot bolt. If it feels pretty tight and resists, then we know that the problem isn't there and tightening it more won't help.

If it does move fairly easily, the issue might be that the bolt is running out of thread and it'll be impossible to tighten, or you need to improve traction between the brake and frame. They make star washers for this job, and if you don't have them consider adding one. The thickness of a washer will also solve the running out of threads issue.

If it is within the caliper, more details -- front or rear brake, type and model of brake, and anything else you have to offer including photos.

Washer looks like this... https://www.amazon.com/Campagnolo-Br-.../dp/B0096XJXZ0 . They break apart sometimes if over torqued.

Thanks for all the responses. It's the entire brake unit that can move. It is FRONT and BACK. If I "ham-fist" it on there, it doesn't really move. I'm taking it in to the LBS to have everything stripped and cleaned. Hopefully, they will have a solution.

I have the same issue on one of my wife's bikes. I torque the nut as per specs and the unit still is loose enough to move. I have to manually re align it before every ride. Drives me nuts.