Addressing a customer issue with this brake having poor stopping power. Trek Madone 5.2 with internal routing, carbon wheel set and new brake pads.
Front brake works perfectly. Rear feels like it’s getting 20% of what it should. Cannot bring pds any closer to the rim and the lever is maxing out when squeezing. Feels spongy but also a lot of friction and poor engagement.
I have replaced the cable and outers and lubricated the new installed cable. Played with the spring tension and arm adjustment screws on the caliper.
Next step I guess is trying compression less housing and a different set of pads?
by eL_cee
6 Comments
Get disk brakes.
Have the pads been bedded in? You could also go to a softer pad, you’ll want to make sure they’re carbon friendly though otherwise you’ll wear the rim.
As a troubleshooting step, run some housing external to the frame and test the brakes. If this fixes it, there is a problem with the internal housing. If not, the caliper may be gummed up. Rebuild with fresh grease on the pivots. The mounting position of those brakes subjects them to a lot of spray and dirt, so they could easily be rusted or dirty in the pivots.
There are a few things it could be. Including everything you didn’t mention, but with no presumption of a lack of knowledge:
– housing can create sponginess. (Unclear if this is what you mean by outers; it certainly doesn’t look new.) I check for this by seeing how the housing moves after the pads make contact, until lever max-out. It should look like it’s twerking, if replacing the housing will fix it. Compressionless will help you. You should run the shortest run possible.
– pad mis-alignment and brake being mis-centered can also create sponginess
– friction will only come from the brake pivots, lever hinge pivot, or the housing/cable rubbing
– what are the brake calipers made out of? Do the arms flex?
Hi, did you use Shimano SLR housing ? It’s mandatory on these kind of brakes for them to function correctly
With cable completely disconnected, do you feel any friction when compressing the caliper by hand? If not, then the problem is upstream (housing or brake lever). Note: I installed direct mount brakes on a Cervelo S3, and I think they’re fantastic, i.e. much more responsive plus they keep perfect symmetry.