Brake caliper corrosion - advice wanted

[Twitchy]

Hi guys, long story short (read my build thread for the long one..) my bike has sat for a couple of years. When I bought the SP2 calipers, I stripped them, the pistons had some pitting and marking;

Also, the pistons;


The pitting is not actual holes or dents in the surface, but raised, like particles stuck there, and REALLY well! Question for the brains trust, do I run over them with some 1200 grit wet n dry, or replace them? US$24 each from partzilla says I emery them, but concerned with the ultra fine scoring letting brake fluid through.

I polished them up with Autosol Metal polish and some old carpet (a trick learned from a truckie with an aluminium bullbar), and they came up pretty good. Now with the bike sitting so long, I have lost pressure in the front brake and clutch levers. So I stripped the front calipers, and found the pitting had gotten a lot worse, and there was corrosion in the landing between the dust seal and main seal (this is the inboard pistons on the left side caliper, the outboard landings have just started to show similar signs), fyi the right side caliper is fine;



And the 2 worst pistons (can't remember if these 2 came from the above location);




So I have bitten the bullet and purchase new pistons (yeah, lotsa $$$$), BUT.. what do I do about the corrosion? Has the corrosion on the caliper transferred over to the pistons? Would the corrosion cross over to new pistons with no pitting? Do I need to rub back and recoat (somehow) the affected area?

Any reasonable advice??

[Wicky]

Did you get aftermarket stainless steel piston replacements?

https://www.ebay.co.uk/i/123726847207

Also carefuly scrape out from the seal recess any corrosion with a fine pick, and on reassemby use red grease to help prevent corrosion building up.

Hard to totally prevent brake rot esp if bike is used all year round esp with winter road set in UK, but just service them a bit more often to keep on top of it.

Edit see you're in West Australia so little chance of Winter road salt - are you near the sea? Calipers look relatively okay - so concentrate on new seals, pistons, red grease new fluid and service them every season.

[Twitchy]

Thanks Wicky, I wasn't aware of the use of red rubber grease for brake system reassembly - that will help a lot.

I sourced new OEM calipers from Partzilla and CMS, at a large cost but considering the state of the originals, I felt I had no choice. 2 things I will never scrimp on is tyres and brakes, they don't function properly at almost any speed and you're in the sh!t!

I also bought new seals, and also the seal kits for the clutch and both brake masters.

I have read more about this problem and one suggestion I have found is to run some steel wool around the seal grooves to help remove the loose corrosion. Or Brillo for the Poms! My old boss was from Newbury, and his wife's name was Brillo, and one day he explained to me it was a nickname because of her curly hair, and then had to explain what a Brillo pad was, I never actually knew her real name

[fabiostar]

Thanks Wicky, I wasn't aware of the use of red rubber grease for brake system reassembly - that will help a lot.

I sourced new OEM calipers from Partzilla and CMS, at a large cost but considering the state of the originals, I felt I had no choice. 2 things I will never scrimp on is tyres and brakes, they don't function properly at almost any speed and you're in the sh!t!

I also bought new seals, and also the seal kits for the clutch and both brake masters.

I have read more about this problem and one suggestion I have found is to run some steel wool around the seal grooves to help remove the loose corrosion. Or Brillo for the Poms! My old boss was from Newbury, and his wife's name was Brillo, and one day he explained to me it was a nickname because of her curly hair, and then had to explain what a Brillo pad was, I never actually knew her real name

a really small brass wire wheel on a dremel type device is better, the brass wire wheel is softer than normal steel wool and wont damage your calipers

[Twitchy]

a really small brass wire wheel on a dremel type device is better, the brass wire wheel is softer than normal steel wool and wont damage your calipers

Hey Fabio, thats exactly what I ended up doing! I have a dremel type tool with flexible extension, gently cleaned up the oxidised parts to clean bare aluminium, installed the new seals, spread some red rubber grease around the area between the two seal grooves and installed the pistons. Hopefully all good.