Caliper grease
I do regular maintenance on my vehicle and have always wondered about the correct lube for caliper slide pins on ATE calipers, which run in rubber bushes. For years I have used copper grease and, until recently, this has been OK. But the last time I changed the discs and pads, the grease had burned away and just left dirt.
I have just bought a complete kit of slide pins and rubbers for both sides which came with two small sachets of silicone guide pin grease. However, on ebay there was a seller claiming that the only lube to use on guide pins was the one he was selling, which was listed as being polyalkylene glycol with a lithium soap base; as far as I could see, the pot (25g for £5) was unlabelled.
His objections for using ‘normal’ slide pin grease were that: 1) Copper grease dries out as the oil base is not heat resistant
(as was my last experience). It also swells the rubbers. 2) Red rubber grease is not a lube as it is vegetable oil and
shouldn’t be used near caliper pins under any circumstances. 3) The silicone grease supplied with overhaul kits is a “poor metal-to-metal lube and does not stop fretting corrosion.” I would very much like to hear your take on this subject. Geoff Martin Polyalkylene glycol has been around for about 60 years and is in a family of products referred to as PAG. The formula is a viscosity builder for mainly water-based products, this one being described as having a lithium soap base. The formula has a wide operating temperature and can be exposed to extreme pressure without suffering from breakdown of the components.
Red brake grease is a vegetable oil product and won't damage the rubber seals of a caliper. It is a lubricant and has been successfully used for years to assemble caliper seals.
Silicone grease is a modern product and has replaced red brake grease due to its high temperature resistance and lubricating properties, while copper grease is technically an assembly lubricant and it is the copper factor that is depended on for lubricating. It is not designed to be used with rubber and its use in caliper slides is dependent on the type of surfaces.
The ebay seller seems to have ignored one other alternative, which is ceramic grease. This is formulated for lubrication of automotive brake calipers, specifically those using electronic ABS braking systems that require a non-conductive grease. Additional uses for it include high temperature anti-seize and mould release applications. It is similar to copper grease, only without the conductivity.
I did find the listing you mentioned and the seller also advised taking a grinder to the brake pads before fitting them to prevent them being too tight in the caliper. This is not something I would advise!
The product comes in a plain pot with no details, but is described as being Molykote G-3407. This is sold by
gannonoils.co.uk, but as far as I can see, only in 18 kilogram or 180 kilogram tubs. I would imagine the ebay seller is repackaging it to sell it on in more practical quantities, no doubt at a profit. He does have a good feedback score and his purchasers seem happy with his product. One pot is apparently enough to lubricate four calipers. The pot is described by one buyer as being around the size of a £2 coin.
I have not tried this product, but from the information available on the manufacturer’s website, I would judge it to be a suitable lubricant to use. The recommendation to stop using any other product is, in my opinion, just a sales pitch – there are perfectly good alternatives.