XTR disc brake squeal

[tomn]

So I've had Hayes brakes forever and now I have a new (to me) ride with XTR disc brakes. Wow...do...these...brakes...squeal. And after the first few rides the stopping power seems to be reduced. They're 06 BR-M765 brakes with the M06 metallic pads. The rotor/caliper looks like this:

http://xoomgear.com/i/p/l/BRKE-31.jpg

So my question is, what can I do to improve stopping power and quiet these brakes down? I have read that using disc brake cleaner on the rotors and pads can help. But I'm wary of putting anything on the pads. I ordered a new set of metal pads (I'm staying away from resin) and some disc brake cleaner but I'd appreciate any advice.

[jabberwocky]

Clean the rotors with rubbing alcohol before putting the new pads in. I don't bother with special cleaner.

I was actually under the impression that metallic pads were a no-no with Shimano brakes, because they use mineral oil rather than DOT fluid. Metallic pads generate a lot more heat than organics, and mineral oil doesn't have nearly as high a boiling point as DOT fluid.

As for noise, make sure the rotors are true and the brake calipers are properly aligned. Its possible that some sort of pad contamination is contributing.

[tomn]

Shimano makes both metal (M06) and resin (M07) pads for XT/XTR brakes. I have read many reviews and user comments that the resin pads work well in dry conditions, have a bit more bite and are less prone to squeal, but if they get wet they fall apart. The metal pads are less grabby but last a lot longer. Basically the consensus seems to be that for $25 a set it's not worth it to use resin because they wear out so quickly.

Thanks for the suggestion of rubbing alcohol, I'll try that. The pads I have on there now seem to have plenty of material left so I don't want to replace them right away if I can help it. I have also heard that if there's contamination on the pads you can burn it off by dragging the brakes on a long downhill. I can only imagine how loud that would be.

[DaveG]

So I've had Hayes brakes forever and now I have a new (to me) ride with XTR disc brakes. Wow...do...these...brakes...squeal. And after the first few rides the stopping power seems to be reduced. They're 06 BR-M765 brakes with the M06 metallic pads. The rotor/caliper looks like this:

http://xoomgear.com/i/p/l/BRKE-31.jpg

So my question is, what can I do to improve stopping power and quiet these brakes down? I have read that using disc brake cleaner on the rotors and pads can help. But I'm wary of putting anything on the pads. I ordered a new set of metal pads (I'm staying away from resin) and some disc brake cleaner but I'd appreciate any advice.

I'd sand the pads, clean the rotors w/ alcohol and re-bed them in. I had issues w/ noise in earlier XT brakes and this fixed the problem.

[pbayne]

Tech info from shimano:

pad compounds: http://bike.shimano.com/publish/content/global_cycle/en/us/index/tech_support/tech_tips.download.-Par50rparsys-0011-downloadFile.html/05)%20Brake%20Pad%20Charcteristics. pdf

some other stuff on their discs: http://bike.shimano.com/publish/content/global_cycle/en/us/index/tech_support/tech_tips.html

Hope some of this helps.

[tomn]

OK now I'm worried. The Brake Burn In Procedure doc says that any time the rotor and pads are replaced, the burn-in procedure needs to be done (10-20 stops on pavement). And if this isn't done the rotor can be ruined.

If the bike is ridden hard before the burn in process is performed the rotor can be ruined. Indications that this has happened are noise and lack of power.
This sounds a lot like what I'm currently experiencing.

I bought the bike used but with a new frame and components in really good shape. I don't know how old the rotor or pads were but they looked pretty new. Ugh.

I guess I have nothing to lose to try the alcohol/sandpaper and see if that works.

[jabberwocky]

OK now I'm worried. The Brake Burn In Procedure doc says that any time the rotor and pads are replaced, the burn-in procedure needs to be done (10-20 stops on pavement). And if this isn't done the rotor can be ruined. What they mean by "ruined" is probably that the rotors will get glazed. This can happen with all disc systems that aren't bedded in (and yes, replacing the pads always requires re-bedding the pads. Thats why I said to clean the rotors when you replace the pads).

Whenever I replace pads, I actually take the rotors off the wheel and hit both sides with my random orbit sander with 220 grit sandpaper on it. This totally cleans the old pad material off and re-polishes the rotor. I then clean it with alcohol and bed the new pads in. If you think your rotor surfaces are glazed, you could try doing this to fix them (assuming you have access to a power sander of some sort).

A glazed rotor is usually pretty obvious (it has a shiny burned surface).

[rizetech]

^ pads can also get glazed - i've never sanded rotors before but it's very effective with the pads, just a sheet and do it by hand so you don't give it any shaping unintentionally, then alcohol with a paper towel or something that won't leave things behind (and is grease-free) to pick up any sanding bits / brake dust, etc.

caliper position may also be a factor, but i'd check that only after carefully refurbing and rebedding the pads/rotors - this is almost always a sure fix. Also make sure there's no oil residue on the caliper anywhere (happens with XTs in the cold - dunno about XTR) since contaminated pads are often a lost cause.