Novice brake maintenance question

When you say squeaking what do you mean?

Is it the pads/disc that are squeaking, lever or calliper?

What brand & model are the brakes.

Shimano BR-M585 hydraulic disc brakes.with LX levers. I imagine they came with the bike so are about 13 years old.

The squeaking comes from the pad/disc and  it's worse after I've applied the brakes making me think it's the piston not retracting fully.

I'd try cleaning/sanding the pads, and cleaning (and a very light sanding) of the rotor first. Or, if the pads are worn, replace the pads.

That's a pretty old LX model isn't it? I think I had one that eventually leaked at the calliper, but was reliable up to that point.

How long has it been in use? what sort of maintenance have they had to date (pad changes, bleeding, cleaning etc)?

Have to checked the calliper is straight and the pads are symmetrically spaced from the rotor?

Does it squeak/squeal all the time or only when wet? (it's not unusual for a wet brake to squeal a bit (IME).

If you want to replace your brake, you need to make sure that the lever and the caliper are compatible. Different types of brakes require different amounts of cable pull, so you can’t just mix and match them. Check the PDF to determine compatible hydraulic disc brake lever and caliper combinations.

SRAM.COM "https://www.sram.com/globalassets/document-hierarchy/compatibility-map/mtb-and-road-hydraulic-disc-brake-lever-and-caliper-compatibility.pdf"

Can I buy a right rear brake from Chiggle and discard the lever? Is the caliper going to be the same for front and rear?

Yes, as long as the fittings are the same. Front and rear calipers are the same.

Also, for different rotor sizes, are the calipers different or is it just mounted in a different place on the fork/frame?

The calipers are the same. The mounts on the fork or frame determine the minimum rotor size. You can fit larger rotors by fitting an adapter to space the caliper out further.

Hopefully a daft question but after 13 years - you have changed the pads, yes?

I'd go with:

1 - Assuming rotors aren't worn (check minimum thickness) Clean rotors - IPA & scotchbrite & IPA again.

2 - Check calliper for leaks, if OK clean& lube piston seals - you can use a small amount of mineral oil on the seals.

3 - Centre pads & rotor correctly.

3 - New Pads - and bed them in properly.

Is the lever a combined shifter and lever? I assume it is as you want to keep the existing lever.

As above, I'd try cleaning everything first and if that doesn't work buy a new caliper or do what you say and buy a cheap set and swap the caliper over. If you're just using the caliper it won't matter if you buy front or rear for post mount brakes.

Theres this caliper only on Tredz for £12.99

www.tredz.co.uk/.Shimano-BR-MT200-Disc-Brake-Calliper-Post-Mount_204033.htm

Thanks all.

Yes I have changed the pads several times in that time!

No it's not a combined shifter - so if I found a right front I'd be happy to replace the whole thing if I can't fix it.

Probably should have clarified - the squeaking is when the brake is not applied. So I'll try the cleaning suggestions but not sure dirt on the rotors would be enough to make it squeak while riding.

If squeaking when riding would suggest its a pad & rotor alignment issue.

Check to see if the rotor is bolted down correctly & all bolts present and see if it's warped, and then re-centre caliper & pads.

Can i use this alcohol to clean the pistons or is that going to leave some residue?

https://ibb.co/3W88ZM9

Cleaning pistons is best done with whatever brake fluid is inside the caliper.

I would slowly squeeze the lever until the piston is protruding 'enough'

Then use a cotton bud or toothbrush, dipped in 'brake fluid' (whatever is inside the caliper) to clean the outside surface of the piston.

Push the piston back in and then repeat the whole process a couple of times.

That will free up the piston movement and should allow them to retract properly and reduce the off-brake noise.