Uneven Pad Wear

[sanjay]

So I was checking/replacing my front pads, and lo and behold!

These are from the larger "outer" pad, and the wear is uneven in both directions. 





The small pad also is uneven, but just barely.

Does this mean caliper rebuild time, brake rotor warpage, bad torquing of the caliper by the p.o., or something else entirely? 

[ukchickenlover]

The front brakes are slide type. It has pistons on one side and the calipar slides when the brakes are applied. I would guess where the caliper slides is sticking. Probably needs cleaning and regreasing.

[starwalt]

I can't quite work this out. Is the uneven wear like a parallelogram or a trapezoid? Or is this just one pad that is uneven?

Parallel might indicate a bent mount or caliper.

Trap shape would really be weird.

Most likely a good rebuild will do you fine. Don't think your rotor is warped. You would be getting a pulsed brake type of  feeling.

[sanjay]

It's just the larger pad that is unevenly worn.  After checking out the caliper pistons, it looks one is stickier than the other, so uneven pressure on the pad.  And when I line it up, it definitely looks like the side of the pad with most wear is the side with the good piston.

I'll clean and regrease the caliper slides (I'm guessing with lithium grease?), toss the pads back in, and probably rebuild next Saturday.

[scratch]

Use graphite or some other dry lubricant.  Grab a pencil for lack of anything else.

[sanjay]

Thanks guys!

I really had to crank on the c-clamp to get the pistons back down.  They're having quite a bit of trouble sliding, and after I reassembled, the pad is dragging on the rotor.  Should be ok for riding tomorrow, but next weekend I think I'll have to rebuild...   

Should you rebuild front and rear calipers at the same time?

[scratch]

Did you open the resivior cover?  That would have made it easier to push the pistons back in (beware of fluid overflow, though; I use a clean rag and absorb some out of the resivior).

You don't have to rebuild both calipers at the same time (you might want to keep one working brake to make sure that everything is allright with the other), but it doesn't hurt either.

[sanjay]

Yeah I did open the reservoir cover, and the rag really helped when I bumped the front wheel and the handlebars swung sideways.  Turns out the piston dust seals are pretty much shot, so a rebuild is necessary (though not urgently).

I need to order the rebuild parts - is there a kit or do I just get the seals and o-rings individually? 

[pantablo]

sanjay, just to be clear with everyone, you are talking about your cbr brakes, correct?

[sanjay]

sanjay, just to be clear with everyone, you are talking about your cbr brakes, correct?

I wish I had a cbr - nope, this is for a gs.  Though there is a 600rr parked next to me that I could borrow a front caliper from... he doesn't really NEED two...

[sanjay]

Bump - I was wondering whether people have used caliper rebuild kits, or just ordered oem parts?

[Chilly Willy]

I wish I had a cbr - nope, this is for a gs.  Though there is a 600rr parked next to me that I could borrow a front caliper from... he doesn't really NEED two...

[scratch]

As I was looking at my leaking bike today, I was looking at my forks and thinking of Sanjay's problem and I think it may be fork alignment.

Sanjay, loosen all four bolts holding the fork brace on, and loosen the pinch bolt on the right fork leg.  Push down on the handlebars without using the brake (maybe put the front wheel against the wall), this will "align" the forks.  Tighten up the pinch bolt first, then the fork brace.

Hope this helps.

[sanjay]

As I was looking at my leaking bike today, I was looking at my forks and thinking of Sanjay's problem and I think it may be fork alignment.

Sanjay, loosen all four bolts holding the fork brace on, and loosen the pinch bolt on the right fork leg. Push down on the handlebars without using the brake (maybe put the front wheel against the wall), this will "align" the forks. Tighten up the pinch bolt first, then the fork brace.

Hope this helps.

Can the forks go out of alignment all by themselves?  I thought it was only possible if the fork brace bolts got loose or if you laid the bike down...

I'm pretty sure it's the caliper, since one piston was way stickier than the other, and the pad is dragging noticeably on the rotor.  But I'll give the fork alignment a shot - seems pretty simple to do.   

Thanks!

[Egaeus]

Any large jolt can move them out of alignment.  They're held in place by clamps.