I’ve been thinking I should try and get some, since my car spends long periods without moving and I’m slightly concerned that the brake pistons will corrode, as happened to a similarly immobile truck I had in the UK.
I’m assuming that a silicon grease will tend to be rubber-friendly, and so should be OK to use on the brake pistons.
I’m in Australia at the moment so it may be easier to find the right stuff here than it is in Taiwan.
Any recommendations?
Where do you want to apply the grease, where the brake pad side are or the brake oil side?
I’ve found that normal grease seems fine on the brake pad side, and I’ve never put any kind
of grease on the oil side. I just put grease in the piston cup and on the back of the brake pads.
Not a lot of course, don’t want the grease to get on the working part of the brake pad. Never
had any problems doing that.
I’m also curious, on the truck where there was corrosion on the brake piston, where was it on
the brake pistons?
I just looked at my shop manual for my scooter and where it talks about servicing the caliper,
it suggests using silicon grease on the piston and on the oil seal. I’m guessing that where you
apply the grease would just be on the walls of the piston that contact the caliper.
Hope this helps…
I didn’t see the truck problem, just had it described to me as an advisory by garage doing an MOT prep, but I’d noticed one of the front brake drums was pretty hot on arrival, presumably because it was stuck. They said they had to clean up the piston due to corrosion, and had applied some grease to it. I asked what kind of grease they used and they said something like “general purpose grease”, perhaps looking slightly shifty while doing it.
I suspect they used a mineral-oil based grease, which could attack seals and O-rings and lead to failure of the wheel cylinder. This was a bit worrying, since a 4 ton truck could make quite a mess of a bus-queue, though I’d hope the failure would not be sudden/catastrophic, and I suppose the corroded piston could also threaten seals.
This kind of thing is one reason why I don’t much like getting other people to work on my vehicles, but I didn’t have much choice in this case, the truck being rather big, and my (illegal) London residence at the time.
So I’m after a high-temperature (rubber-friendly) silicone-based grease for the piston sides. Ideally, it should also have anti-seize properties so I can use it elsewhere in the braking system.
A bit of Googling suggests Permatex Ceramic, Molycote M-77 (though spec says “compatible with many elastomers - test for compatibility” - Oh yeh? HOW exactly?, so probably not that), or Sil-Glyde as possibilities. Might not have time now for mail order to an address in Australia so I’ll have to see what I can find in the shops.
Oh, and there’s Bendix ceramlub, which may be the same stuff as the Permatex.
I’ve got personal objections to Honeywell, though, so that’d be a last resort.
Local car place had a couple of products that I’ve heard of being used on brakes, but which aren’t specified for that use:-
Permatex dielectric grease (#81150), which is dimethylsiloxane and fumed silica - should be rubber friendly
CRC thread lube (SL35925), which is an anti-galling/seizing compound, from the MSDS essentially a mineral oil/lithium based grease, so not rubber friendly, though it might stop the crappy wee cross-head screws found on motorcycles welding themselves into the ally castings, like they otherwise do.
They also had a “traditional” rubber-grease, based on castor oil (probably in combination with bentonite, though it didn’t say so on the tube). I’d heard of these (I took their existence as partial support for my dodgy DIY veg oil tyre treatment not being too damaging) but castor oil, though rubber-friendly, is quite a lot less stable than mineral or silicon oil.
Of these three I’d probably go for the dielectric stuff, but I’ll see what else I can find.
I could only find the Bendix (= Honeywell, unfortunately) Ceramlube stuff from Repco. They had it in big 1000 years suppy bottles/tubes for 35AUS$, or wee one shot sachets for a couple of bucks, so I got a couple of the latter. Sod’s Law would suggest I’ll find the Permatex stuff in Taiwan next week for half the price.
Alladdin’s Cave-stylee tool stores are everywhere here (probably like the US, though I don’t remember being in one when I was there.) Going to miss that back in Taiwan.