pistons with 3 in one silicon spray.

I did and have lived to regret it tonight . 😳

Scenario yesterday changed wheels and went for a short ride with the dog the back brake was just touching and making a noise.
So this morning I knew I was going on a ride tonight so had a quick look and thought I had a sticky piston ( Hope Mono M4`s)
so thought a quick fix would be a tiny lube with silicon spray would do the biz .

Result it certainly sorted the sticky piston out .

But and this is my theory my back brake was suddenly very draggy when off and the lever nearly solid after the first few applications .

this meant a tour of Gisburn forest with Smudge and every climb became a granny ring torture fest for me and all the wildlife in the vicinity hearing the noise and vanishing .

I think the pistons which rely on the seals to pull them back off had now become slippy and didn’t retract so the pistons kept pushing out resulting in the extra resistance training I would have rather done without .

Bike brake sorting session tomorrow morning 😥

Silicon spray might have caused the seals to swell.

Were your lights ok though? 😉

Re-title thread “WARNING Don’t go near your brakes A) with lube B) if you haven’t tinkered with brakes before? 😆

Lights were great 😀

B) 😳 Tinkered with lots of brakes and lesson learnt wot not to do 😳

100% silicon spray is fine on rubber pistons and keeps them clean but 3 in 1 has other ingredients which may not be ok on rubber pistons.

The spring in the master cylinder helps pull the pads back. even if it didn’t, the rotors would push them back to an annoying light scuff. sounds more like a mineral oil causing the seals to swell and bind on.

silicon spray shouldnt have done any harm unless it was a mix of something?

Some oils are petroleum based, which is no good for rubber seals, makes them swell.
Silicone should really have been ok though…..

BB7s are the answer…

Brake pistons don’t move through the seals when you apply the brakes; anybody who has tried to remove a piston will know that. It’s the flexibility of the seals, which allows the pistons to move and then spring back. As the pads wear the pistons do creep through the seals very gradually when you grab them extra hard but they don’t slip back.

Possibly you have altered the hardness of the seals or the silicone allowed the pistons to creep through then the seals settled with the pistons too far out.

Possibly you have altered the hardness of the seals or the silicone allowed the pistons to creep through then the seals settled with the pistons too far out.

Globalti that appears to be what is happening now its daylight and I can see the action close up the pistons are coming out and not returning
and after a few pumps of the lever they are holding the disk quite hard
so as an attempt to spin the wheel gets a quarter turn if that .

It would appear I have buggered the seals good and proper . 😥

Probably something in the 3 in 1 then, as manufacturers use silicone assembly grease on the pistons and seals when putting them together.
Edit- if you can’t get anybody local, give me a shout and i’ll get them sorted for you, you’ve helped me out in the past, one good turn and all that.

Thanks Coatesy will do if stuck

currently trying
Have pumped the pistons out as far as I dare and given them a good clean
and a smidge of brake fluid now trying the zip tie the lever back for a while and see it that improves it while I order some new seals .

I find I replace the seals in my M4’s rather more than I’d expected to, (even with clean, unworn pistons) – mine often seem to end up with a piston that either sticks in, or won’t retract properly …

Happily, M4’s do have great spares availability (IME); they strip down fast, go back together properly and bleed through quickly and easily too, in a nice, predictable way, so whilst it’s a bit dull to do it too often, it’s not an especially onerous job. (Fluid smell aside).

If/when you get to the ‘in bits’ stage, see if that piston has picked up a bit of wear – hard to imagine how this happens, given the forces / travel / materials, but it’s something that can cause a bit of leakage, and/or attract ‘muck’ – which can make the piston sticky (more sticky).

I usually end up swapping pistons around between calipers when I’m rebuilding mine, albeit non-deliberately, due to everything being cleaned at the same time.

Immediate problem sorted I have swapped the back brake with the one off the FS bike .

Might be time to get a new one. As this one is pretty old now .

Of the four brakes I have. 3 are Tech M4. And the bad one is an old Mono M4
Be a good time to have all four matching