Brake Caliper Grease

I'm having one of my 'get it right you fool' moments.

Last time I rebuilt my rear brake caliper I think I made a bit a hash of it, mainly to do with 'sticky' pistons. I don't recall using the little pack of grease which came with the kit.

Having Googled some tips, I can't see anybody using the grease to rebuild brake calipers. Most people say that using fluid to install the pistons will lubricate them.  I am wondering which parts should be applied with 'brake fluid' and which parts with 'grease'? The inner seal in the bore is obviously a fluid seal. The outer seal is a dust cover but does it also act a grease seal to stop the fluid and grease mixing?

If so, it means coating the pistons and bores with great dexterity. Have I missed something?

....bearing in mind that my Marbles are already loose.

Hi Chris.
As you might be aware, I re-ferbed my Front and Rear calipers recently using Stainless Steel pistons in a hope that the salt won't stick to them. I also clean the piston bore with a white scotch pad(non scratch) because the crud gets in under the seals, I made a special scrapper to scrape the seal grooves because of the corrosion build up in the bottom.
I always use the red grease to seat the dust and piston seals in the caliper then a smear of Dot 4 on the pistons to push them into the calipers.
My rule of thumb is.... if you can push the pistons in but can't pull them back out with just your fingers there's still crap in the seal groves causing them to bind on the piston
Then bleed and test for binding, the usual faffing.

Hope this helps.

Be safe, be seen!

Hello
I usually wash my brake stuff in ethanol alcohol
scrape the piston packing groove with a home-made special tool
polish with fine sanding cloth, lubricate pistons and cylinder inside with the red brake grease from ATE + a little inside on dust seal before assembly bleed with the cheapest suction brake breather on aliexpress and thanks to this super forum my glue clamps on brake handles held for 24 hours = super brakes

Sounds logical but if there is red grease on the bore seals, does it have a nasty reaction with the brake fluid when you insert the pistons?

I'd be interested to see your bore groove cleaners.

one of the tools is made of 2mm welding wire with a 180 degree bend
the other is a leftover sheet metal strip with a 90 degree bend
unfortunately can't post any pictures, guess have to go to training for that
Stefan

Just for information this topic was in "Introductions" so I moved it over to "Maintenance". Carry on!!!

Thanks Glenn. That'll be me not paying attention again.

I've dismantled my used rear brake caliper and it all seems to be in good condition. I've removed some crud from the pistons using Autosol Metal Polish.

They look like stainless steel pistons;



After doing some Googling I can't decide what to 'wash' them with to remove traces of metal polish. Any recommendations welcome, particularly if you've ever done this.

Hi Chris.
The thickness of the side wall of the piston tells me It's Stainless.

Firstly, don't forget to clean the bottoms of the seal grooves in the caliper.

I just use a rattle can of brake cleaner to clean the sight window and to remove any possible residues then wipe off with kitchen towel or leave to self dry where applicable.

Hope this helps.

Be safe, be seen!

Just put all the parts in the dishwasher. What could possibly go wrong?

Ha! You may jest my friend but after all the manual labour involved in this job, the thought had occurred!

Well, I'm rebuilding my rear brake caliper and confusion between using brake fluid to lubricate the new seals with brake fluid or grease has driven me to despair.

After much online research there seems to be no definitive conclusion. So, I am going to lubricate the outer and upper and lower edges of the new seals with red rubber grease when installing the seals themselves, this will protect the rubber when in situ. Then. I will apply a small smear of said grease to the inside surfaces of the seals which make contact with the pistons. When I push the pistons into their bores the grease will allow a free slide into the bores.

After that I'm hoping that the pistons will have swiped off most of the grease from the inner surface of the the seals and thereby not contaminate the new brake fluid when refilling the system with new brake fluid.

The general opinion is that brake fluid is not a good lubricator and dries over time, apart from attracting moisture and causing corrosion on the pistons and seals.

Wish me luck.

Using grease on seals is a good idea, especially in seal grooves, very effective keeping moisture out, brake fluid does the opposite (hygroscopic), just wipe any excess from outside areas to keep dust/dirt from sticking, any grease that mixes with brake fluid should flush out when brakes are bleed.