Rear Brake Caliper Cleaning

I have a cunning plan to clean up my stripped down rear caliper. I have ordered some rotary brass wire brushes for my Dremel to clean out the seal grooves properly. I intend to run the brushes inside the seal grooves only. However, I would like opinions on whether any stray brass bristles might scratch the shiny bore surfaces.

I am assuming that brass, being softer than the caliper metal, would not damage the bore surfaces.

Advice welcome please.

Hi Chris.

Any chance of a picture or two showing the inside of the piston bores. The reason I ask is because the callipers are only aluminium, so do a test patch externally to see how the brass brushes mark up the ali.
Personally, I would use a none scratch (white) scotch pad trapped between a split pin in a drill to buzz up the piston bores.

Hope this helps
Be safe, be seen!

Hi Chris, Ps.

The OEM calliper pistons are surface treated in production so any rust pitting to their surface is irreversible, even if polished up like new (makes them rust even faster) that's why I posted about buying stainless pistons while they are still available.

Be safe, be seen!

I have carefully scraped the seal grooves with an angled pick to clean out any major debris, then used a brass brush to finish off. Then give the caliper bores a good flush out with brake cleaner.

If the bore areas are "shinny" they are probably ok, what is critical, is the piston coating condition and the seal groove corrosion/wear, any heavy corrosion and/or too much mechanical corrosion/material removal, i.e., wire brush, pick, etc. that will distort the seal groove, will render caliper useless, the seal grooves on motorcycle calipers are machined slightly tapered, this allows the square seals to flex and retract piston away from rotors when brake is released, reduces pad wear/heat, prevents rotor warping, etc., etc.

Sorry, but heavily corroded calipers or bad pistons should go in the bin, IAC using brass/steel wire brush to remove aluminum corrosion not good, dissimilar metals contaminate the aluminum, causes more corrosion eventually.

OK, so here are some pics of my replacement caliper:

Here are the bores and grooves:



Here are the grooves:



Here are the grooves and the piston(s):



Here is how I want to clean the grooves with brass rotary brushes:



I can't decide whether the grooves are clean enough for the new seals or whether a clean-up with the wire brush might ensure the seals seat themselves more securely. Could the brass brushes do any damage to the grooves?

Opinions welcome.

My go/no go decision with cleanliness is if I can feel any surface roughness. I just swipe my angled metal pick gently around in the top/bottom corners of the seal groove feeling for drag or bumps, and if there is none then I consider that acceptable. What you don't want is for corrosion or debris to be forcing the seal harder into the piston as that adds drag that you don't need.

AFAIK a brass brush is perfectly OK on the alloy of the caliper body, and I use a green Scotchbrite pad to gently polish off any build-up on the piston.

Hi Chris.

I think people have covered most of the subject.
I would still DO A TEST PATCH EXTERNALY on the Ali with the brass wire brush because some makes are brass covered steel wires used in the brushes (particularly cheap ones).

Be safe, be seen!

Good idea Johny. They're Dremel brushes so I'm hoping they're the real deal.