I’ve put gt 85 on my pistons on my elixir r brakes and it’s help my pistons not stick

I am good

Certainly modest!

It might not help long term though. The solvent in stuff like gt85 might screw up the seals over time (make them swell). I would use a thicker grease, rather than the spray on stuff in future.

Glad that you freed them up though.

one to bear in mind if you sell elixir R brakes in the future…

in all seriousness, best use the same oil that is inside the brakes as you know it won’t degrade the seals.

Ruined the seals on my elixirs

Its silicon based grease you should use on pistons and seals.
It lubes but doesn’t affect the rubber seal. I occasionally remove the pads, extend the pistons out spray inside the caliper with silicon lube spray and clean the pistons with a cotton bud.
I had this info from speaking to hope a while back.
Andy

I spent about 5 years doing the same with WD40 on my Hopes. They worked fine.

WD40 do a silicone based spray that is for use on rubber seals.

Never used it on my bikes, but used plenty on airpistols

Its the wd40 one I use. We did some industrial testing for them at work for their new range.
I had a bottle to do some testing myself.
http://www.toolstation.com/shop/p89943
Also had some lithium grease which I haven’t used properly yet. interesting stuff though. i sprayed a bit on my front mech and thought no more till i came to ride home and wondered what was all over my mech. goes on clear (like wd40) but dries white and thickish.

Trimix, is the solvent used in wd40 the same as gt85? Are Hope seals the same material as Avid seals?

Having done a lot of work previously compatibility testing various types of rubber with various solvents, I am very wary of just spraying unknown solvents onto unknown rubber material. The degradation can be massive and can occur almost instantly or over a number of months.

Andysredmini says he has spoken to Hope about the suitability of a certain spray on their products, but it would be wrong to assume that what works for Hope will work for Avid. Even different suppliers of the ‘same’ rubber can yield differing results.

It’s one of those things that might be ok, but might not.

I hope this doesn’t sound like a dig. It isn’t meant to. Just trying to suggest that people don’t randomly spray ‘some slippery stuff’ onto their seals assuming it will make things better. It might in the short term, but might make things a whole lot worse in the long run.

Brake pistons don’t move through the seals each time you apply the brakes; the flexibility of the seals is what allows them to move and the pistons only creep through the seals as the pads wear. Lubricating the seals won’t make any difference.

globalti – Member

Brake pistons don’t move through the seals each time you apply the brakes; the flexibility of the seals is what allows them to move and the pistons only creep through the seals as the pads wear. Lubricating the seals won’t make any difference.

So why is it that one side ends up ‘sticky’ then (doesn’t extend as much as the other side)?

I’d guess because of crud build up over time in the piston bores and on the pistons themselves. Probably also degradation of the lubricant on the seals too.
If done regularly i would imagine it would help reduce sticky pistons ocurring in the first place.

Does anyone know what the elastomer material that is to make the seals used in disk brakes? Generally Buna or Viton elastomers are the most common for this type of duty, both of which are suitable for use with silicon greases. Many solvents will attack Buna elastomers. Viton will resist solvents better.
I don’t know what seal types are used but I look at elastomer compatability as part of my job so if anyone can let me know I could draw up a safe to use list of oils, greases etc.
I agree that using the hydraulic fluid that is recommended for the brakes is the safest course of action.