Road disc brake problems

Quote:

The advice from kev-s is good.

Oi! I said all that first 

I think sanding rotors is perfectly OK and seems to be an accepted maintenance thing with disc rotors, more for when you are changing pads (especially if you are changing compounds) as the rotor will apparently hold onto pad material from the old pads which doesn't always play well with new pads.

Also something to do with bad bedding in which can deposit differing amounts of pad material around the disc which can set up a sort of stick/slip reaction which can cause squeel.

Could anyone tell I've been trying to cure a set of squeeling discs recently? My next road bike will be back to rim brakes, I can tell you that much... 

I use their discs and pads with my Spyres but I'm about to fit 805 calipers and they don't seem to do the pads yet.

The advice from kev-s is good.

Bin the pads. Trying to decontaminate is a waste of effort.

Sintered pads last longer and are less prone to contamination (but not immune).

If you go to Disco Brakes, you can get sintered pads for a fraction of the Shimano organic pad price. 

www.discobrakes.com

I've used them for both Avid and TRP discs for several years and love them. 

It amazes me what people will do to a set of contaminated pads!!

Chuck them in the bin, clean your rotors with isopro alcohol (dont sand them) clean the calipers with isopro alcohol, check for any obvious signs of leakage from the pistons, where the two caliper halfs join together and brake hose joints

Fit some new cheap pads, bed them in and see if they get contaminated, if they do then you have a leaking caliper, you may not be able to see the leak but you will have one

If in warranty contact the shop you bought them from or the distro who import them and they will ask for it back and do a pressure test on the caliper

This is the process i went through with a Shimano XT caliper

The distro sent me a brand new caliper and pads and no more leaks!

I don't know a whole lot about disc brakes, but personally I'd be really wary about sanding the rotors to clean them. If they're 'contaminated' it will only be surface as oils etc won't soak in to the metal, so just take the wheel out, wipe it with a degreaser until shiny, wash with soap and water and put back on the bike. Sanding with coars (,400 grit sand paper) I think would have a high chance of affecting brake performance, and increase likelihood of contamination of the pads. IMO. 

With most brakes (cars, motor bike etc) one the pads are contaminated with oil, it's something of a fools errand to try to decontaminate them (or so my engineer Dad told me)

I'm a little out of touch with Shimano brakes, but I think leaking callipers causing contamination was a fairly well recognised problem.

It'll drive you crazy because apparently the leak is small enough that you won't be able to trace it.

In my experience life is too short to try and recover contaminated pads. Bin pads, buy new ones and clean everything thoroughly before refitting.

Spend the next couple of weeks being hyper careful about oiling the bike etc. so you can be sure you haven't contaminated the pads yourself. If they develop the same problem it's probably worth considering that they're leaking. Raise it sooner rather than later with the shop you bought them from so you have a better chance of raising a warranty claim.

If you search the google term 'singletrackworld: leaking shimano' you should probably find a thread where someone identified the issue and a possible fix (replacement o-rings to fit between the calliper halves).

This is why I've not bought Shimano brakes in the last couple of years, my dad's had two duff sets...

Move onto sintered pads, much much quieter.

Um, sounds like your pads are contaminated. Rubbing them ain't going to help with a serious contamination.

As mentioned, work out what is contaminating them, stop that happening again, purchase new pads. Enjoy nice brakes.

I completely messed up on teh MTB the other week. Had a bit of contamination in pads from a bit of gt85. Thought I'd just burn through that no problem... a few draggy and hard stops will get that sorted. I was wrong. The noise got worse, the braking less effective... I squeezed harer and harder. 

Turns out, my squeezing had exposed a previously undiagnosed crushed o-ring, and I had forced fluid out and onto the discs and pads. 

Lesson learnt. These days I am very careful to not let any cleaning substance near the pads, and will clean the rotors with alcohol based spray post any cleaning / maintenance as a matter of course.

DIsc brakes are sensitive little beggars in my experience. 

I too was a fan of a good scrub with a wire brush and alcohol, but then I found these, and at the price, contaminated pads get one chance at rehab and then get binned if they fail to clean up.

https://www.amazon.co.uk/gp/product/B005PVLIJQ/ref=oh_aui_detailpage_o01...

HTH

A mechanic told me to put the pads face up in a small puddle of isopropyl, set it alight, rub down with Emery paper and then repeat the fire bit and they should be good. I bought a new pair due to being time short before an event so can't testify as to whether this works.

Only contaminated when I had to lube the sides of the pistons as they were sticky

Vibration sounds like large disc run-out from being warped or lumpy deposits.

Pad wise, I only get squealing in wet weather if I haven't cleaned the pads for 3/6 months.

I rub the pad faces against each other under the tap with some washing-up liquid as a degreaser.

Keep rubbing until there is no mucky paste left.

The pads then get wiped with alcohol and refitted.

I'd be concerned that uncontolled heat may detach the pad material from the carrier.

domestos on the rotor braking surface. rinse. dry.

window cleaner (acetic acid) on sintered or semi-metallic pads, let soak, wipe the glaze and muck off. rinse. dry.

bed everything back in.

my commuting bike is generally fine until there's a heavy rainfall after periods of dry weather, and then there's the sense of the pads just sliding instead of adhering.

How are you contaminating them do you think?  I've got over 10k km on my set of Ultegra disk brakes and have only had to replace the pads once due to wear - I've never had any contamination issues.

From a maintenance PoV:

- Never use spray oils anywhere near the brakes, tbh I don't use any at all on that bike.

- I use wax rather than oil on the chain, much cleaner and easier to maintain.

- it's Di2 which might help, but I limit myself to a drop of wet lube on the moving parts of the FD/RD, let it soak in a bit and then wipe the whole thing down to remove any excess

I'm afraid I've nothing much useful to add on fixing contaminated pads; the one time I got dot4 fluid on my pads on the MTB when I cocked up some maintenance, I ended up replacing the pads.