Shimano CX77 Braking Issues

rider25

Hi,

I've a Canyon Inflite with CX77 mechanical disc brakes. After a recent (very) wet ride on the road the braking performance is shocking. Previously in the dry the brakes were really 'keen' but now, a few dry rides on from the wet ride I referred to, the braking performance is still very poor and I'd say worse than that of low end rim brakes. To the point where I can apply the brakes and still pedal forwards.

Alignment of the caliper and pads seem fine and the calipers seem to squeeze the disc properly - it's as if the pads aren't performing their job. However, they are near new and they did seem to stop me on a sixpence in the dry.

I'm referring to both front and back, btw.

I've had the problem before (rear brake) but put it down to me possibly having contaminated the pad with degreaser or similar. Looking back though, it coincided with a wet ride.

I'm sure the answer's probably obvious but it's got me stumped.

Any pointers would be welcome!

Ta

meanredspider

Definitely something up but almost impossible to diagnose remotely. Contamination seems most likely - something oil-based I'd guess. But I'd not be confident with that diagnosis.

rider25

Thanks for responding. Perhaps you're right but for both occasions to be immediately after a wet ride is puzzling… and for them both to be affected this time around. Hmmm.

antsmithmk

It could be that they were supplied with organic pads... which wet and grit go through like a hot knife through butter.

I've gone from new pads to plates in the course of 45 minutes in a cross race. Replace the pads with something metallic.

The other thing to consider is did you initially bed the pads and rotors in? It's probably the biggest mistake being made by road riders coming to disks. In the first 300m of your first ride you really need to perform at least 10 emergency stops to ensure the pads coat the rotors.

rider25

Cheers for you thoughts, antsmithmk.

The pads I'm using are these:

http://www.bike-discount.de/en/buy/shim ... GwodsOUAkA

There's no noticeable wear on the pads despite their poor performance. As for bedding them in, they are used primarily on my commuter so plenty of hard stopping.

Any recommendations for semi metallic pads?

rider25

Sorry, initially read that as 300 miles when you clearly meant meters. No I didn't in that case. As I say though, braking performance in the dry was spot on.

meanredspider

The bedding in procedure needs to generate real heat in the pads & discs. With the best will in the world just commuting, unless you have a good steep hill with several hairpins, isn't going to do it. The disc needs to be hissing on contact with water. The process is best done on a downward slope - get up to a good speed then brake with one brake until you don't quite stop - then speed up again and repeat. I can normally get them hot enough in about 6-7 stops. Then ride for a bit to let it cool down. Repeat for the other brake (harder to do on the rear brake as you must NOT lock the brake in this process).

Organic pads are perfect for road use. I'd only go for metallic off-road (or very muddy roads) - they don't work quite as well as organic but resist abrasion better.

rider25

Thanks both. Will switch the pads this weekend and bed them in properly.