bartonbeau

I recently fitted new pads and discs all round. The braking was much improved but I braked hard at high speed (90+) and the rear end felt skittish. I had the rear calipers off today and while the outer pads were fine the inners where only making contact over about a third of the disc brake surface. I wound the pistons out (very stiff), pulled back the rubber seals and examined the pistons. They were very clean with no rust or pitting. I cleaned them up with brake cleaner and silicone spray on the rubbers. They wound in a lot easier. I also removed, cleaned, and regreased the slider pins with Ceratec (as recommended by someone on here!)

Anyway my question is, should I have lubricated the pistons, and if so what with? I've never had a caliper completely to pieces, but if I wound the piston right out can I remove it to properly clean it or do I have to take the caliper off to rebuild?

Thanks in anticipation for any advice.

RobAp1

It doesn't sound like a piston issue, I've seen similar before.

Check the orientation of the slots or cut-ou. In the pistons there are small locating pegs on the back of the pads and if these don't like up in the slots/cut-outs then it will apply uneven pressure to the pad causing odd braking feel and uneven wear

Gaffa

I refurbished my callipers and refitted them at the weekend, the pads did not have any locating pegs,
I did not check the make of the pads,

so should OEM pads definitely have the locating peg on the inner pad ?

When I clean motorcycle calliper pistons, I spray them with GT85 which is a PTFE spray and is rubber friendly.
I would be inclined to use the spray tube and spray a little under the rubber boot rather than removing the piston completely.
If you do remove the pistons you should replace the seals.

RobAp1

It probably depends on the brand of pad. I know my ferodo's have pegs but not sure on oem ones?

noodels

Grind them off,they are a pain in the butt

Gaffa

that's sounds like a good idea

RobAp1

Or just fit them in where they should go? There must be a purpose to them other than to annoy?!

noodels

Grinding of the nipple allows better adjustment or the pedal,
normal in the garage/repair shop world

BenRNBP

I've never quite understood them, do they have a self-adjuster or not ? Is the idea that you are meant to just wind them out until the clearance is appropriate (and when your pads wear you have to unwind them some more ?)

RobAp1

I think they're maybe meant to stop any possible twisting movement of the piston> I'm not really sure, but i've always fitted them into appropriate spot and never had any issues so far. The hydraulic side of the brake system will self compensate for pad wear, and that wonderful self adjuster on the handbrake should take care of itself until it seizes up