Avid BB5 disc pads worn crooked

JamesB

Have been noticing recently that rear BB5 on winter disc equipped bike has been fairly ineffective, can`t even lock up back wheel

I took pads out and noticed 1. that arae of wear is restricted to a section in middle of pads--would have expected wear to be even, and 2. the pads were worn at an angle, thicker at top, thinner near wheel centre.

When setting up brakes took great care with ensuring mfr instructions followed so that moving pad was set closer to disc than fixed pad (did this by loosened off anchor bolts, putting a business card between moving and disc, tightening fixed onto disc, squeezing brakes fully on, tighten anchor bolt).

Anyone found similar, any advice ? Have just put in a set new pads as with uneven wear old ones can`t , I think, be set up properly again.

ugo.santalucia

Well, the caliper is not aligned properly, as it seems... There is no other explanation

Monty Dog

Yes, either caliper mis-aligned or the pad wasn't seated correctly in the caliper (less likely)

JamesB

Yes the caliper did look a little askew, but can`t undertsand how it could be as setup should have made it square on given CPS bolt set has domed washers for all angle adjustments and the rotor should have enabled square on adjustment with methods used

sungod

the adjustment can be fiddly, when i had bb5s i found that it could take a couple of goes to get the caliper correctly aligned

i always set mine this way and they worked extremely well...

i never used a card/shim, just loosen the bolts, pull hard on the brake lever, while the bolts are loose give the whole thing a good jiggle to help centre the washers etc., then tighten

once tight, look carefully at how the calipers close on the disc, if the disc looks like it's being moved/twisted have another go

JamesB

just loosen the bolts, pull hard on the brake lever, while the bolts are loose give the whole thing a good jiggle to help centre the washers etc., then tighten

won`t this then place rotor too close to inboard (adjustable pad) ?? From what i recall from Avid instructions rotor should sit a third distance away from moving pad? BUT if it works well for you I`ll give it a go !!

Monty Dog

I don't use any packing when positioning the calipers - you'll get some minor pad rub on the inboard and just back-off the adjuster a couple of clicks.

JamesB

What about all the muck on road being thrown on to rear rotor (gets grime and grit on it each ride at moment, front is clean though), for me this has often resulted in scraping . grinding? Doesn`t running very close inboard pad make this a problem?

sungod

i went through some pretty crappy rides on them, never had a problem

if something gets in there it should clear with a light touch of the brake lever

hose down at end of ride

woolwich

I have had mud stuck in the rotors vents, right on the brake surface, I assume it must have some sort of additional grinding/ wear effect.
Whilst I agree with everyone about your alignment being slightly out. This does not explain why you have wear only centre pad. Grime might explain it, agitate it with a pokey thing as well as using water.
Also might be a warp or wripple centre track? You could test with a decent straight edge or metal ruler, unless your lucky enough to have a surface plate. Although to be honest you would probably feel this as the bars when you brake.