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Remove Stuck Brake Pistons Safely
Fix Date 11/12/15
By Ren Withnell
I learnt to do the following trick when trying to get the pistons out for cleaning on my 4 pot blue dot Fazer 600 callipers - so this works even when access is a little restricted. As you can see in the video this is demonstrated on a CBF 125 calliper with some seriously corroded pistons - these brakes have 47,000 miles on them now and are way way way past their best.
You will need some circlip pliers that can "expand" or open by pushing outwards. The idea is to use this expansion to grip the inside surface of the piston. If we were to use ordinary pliers or vice grips on the external face of the piston this would leave grip marks, scores and scratches on the outer surface of the piston. As the outer surface mates with the delicate rubber seals within the calliper any damage may rip or tear the seals. The inner surface is unimportant, so any scratches or gouges here are unimportant.
Of course the piston is too big for the circlip pliers. To resolve this I simply slip in a suitable size socket. The best thing about sockets are that they come in a wide variety of sizes which means this will work on a wide variety of pistons.
So now I shall leave you to watch the video and all will be explained.
Reader's Comments
Henrik said :-
Thanks for sharing, thats a nice methode !!! perhaps some wd-40 or anti-rust spray over night will make the operation more gentle to violate the inside least possible.
01/01/2000 00:00:00 UTC
Ren - The Ed said :-
Hey Henrik. Cheers for that, I was rather pleased with myself when I worked it all out. Now you can correct me if I am wrong but I've always been warned off using WD40 or ANY oils other than brake fluid on brakes. It could just be internet nonsense but some folks suggest anything other than brake fluid can cause the seals to swell. I'm not a seals or rubber expert so I can't say if it's true or not.
01/01/2000 00:00:00 UTC
Ian Soady said :-
I agree Ren, any mineral-based oil will rot the seals. Brake fluid has a different base (apart from some 1950s Citroens but I assume we're not talking about them!). You will be renewing the seals as a matter of course but WD40 or other penetrating oil does in fact penetrate everywhere you don't want it.
Good method though. On the other hand, if the pistons are seriously corroded I wouldn't be reusing them so would probably go for heat and mole grips......
01/01/2000 00:00:00 UTC
Ren - The Ed said :-
Cheers Ian. I am in fact hoping to see if the engineers at work can rustle me up some stainless or brass pistons rather than actually spending my own money. Luckily I purchased a used whole brake calliper off fleabay a while back so that's on the bike and I'll recondition this one in the mean time.
I know the pistons are cream crackered (knackered). I was just using them to demonstrate in this video in case anyone's trying to get their own out.
Would I be correct in thinking WD40 and other such oils can affect all kinds of seals? Engine oil seals...fork seals...shock seals...?
01/01/2000 00:00:00 UTC
Henrik said :-
You should be pleased with you self, I am also not an mechanic oracle, and likely less experienced in general, but trying to catch up on it, with big interest. Sometimes when seeking info 10 places, get 10 different answers :-)
Maybe what you say about oil is true, anyway I would be tempted to do it, and think that infact I did once with the MZ. with no problem I am aware.
That being said I also always clean metal-parts very carefully after, with some "anti-grease" liquid in DK called "sprit", kinda alcohol. And things such as seals and dustcovers I always replace with new ones, to "start on a fresh", and be absolutely sure it will work for as long as possible.
Maybe owerkill, sure, and if seals are rare and hard to get, or extremely expensive, one should try to save them from damage obviously,..
Maybe some experts can step in, each one teach one :-)
01/01/2000 00:00:00 UTC
Ian Soady said :-
"Would I be correct in thinking WD40 and other such oils can affect all kinds of seals? Engine oil seals...fork seals...shock seals...? "
No because they're not made of natural rubber but stuff like Viton etc which is synthetic and in fact oil-based. Brake seals are made of natural rubber and so are attacked by mineral oil. In the same way, you can pour engine oil all over your paintwork and it won't harm it, but don't try that with brake fluid (except for DOT 5 I believe which I think is synthetic).
01/01/2000 00:00:00 UTC
Henrik said :-
Ian: so the conclusion seems to be: that one should try to avoid oil as far as possible when working on calibers where the seals are yet not removed, and if its nessesary to use oil for some reason one should renew the seals and clean the calibre-house very carefully before adding the new seals ???
On a related note: is the brake-seals normally the only part made out of real rubber on a mc ? if not what else ?
Dust-covers often appears as being a bit stiffer so I guess not rubber ?
Last, I often heard that real rubber should/could be maintained and freshed up with clean silicone liquid, so is that the thing to use for braks-seals then in orde to sustain their lifetime ?
01/01/2000 00:00:00 UTC
Ian Soady said :-
Hi Henrik.
I would actually say it's safest to NEVER use mineral oil on any brake component. It's not only the caliper seals, also the master cylinder seals and of course the brake lines.
You can get special rubber grease http://www.redrubbergrease.com/ but for most of us we use so little it's not worth bothering. A little bit of brake fluid is all that's usually needed.
I'm not sure what you mean by silicone liquid. In my mind, brakes are too important to take chances with.
01/01/2000 00:00:00 UTC
Steve Latchford said :-
I've done lots of brake calipers over the last 30 odd years, don't ever re use brake seals, your life could be at risk, they cost practically nothing and you know your brakes will be superior when they are fitted, also if the caliper seals are worn then the master cylinder seals will have some wear as well, even if you don't think so, they have done twice the work because they travel further. Believe me I have just done a bike with 24 seals and they really do work like brand new factory fresh items.
As for stuck pistons, all I do is remove the brake pads then place the caliper back on the mounting and pump the pistons out with the brake lever until they stop on the discs. Yes I know the Pistons are now not all the way out but they are out far enough to be nice and loose to then use the editors method of removal.
To top it all off make sure to flush all the brake fluid out with new fluid, I use a syringe at the bleed nipple end and pump upwards into the master cylinder, removing fluid as it rises with a second syringe, just make sure to keep the lid on the master cylinder or it will squirt 4 feet in the air usually all over your bike.
This method proves that any air and old fluid can and does travel through the tiny transfer hole in the master cylinder piston, so any tales of holding the brake lever in overnight with a cable tie to expel air is complete nonsense, this will only hold air in the system as you will have blocked it's way out. If air makes its way up to the master cylinder let it escape naturally into the pocket of air in the reservoir.
01/01/2000 00:00:00 UTC
Ian Soady said :-
"so any tales of holding the brake lever in overnight with a cable tie to expel air is complete nonsense, this will only hold air in the system as you will have blocked it's way out. "
That's what I've always thought as well, and for the same reason as you, despite everybody saying the opposite. The only slightly credible mechanism I've heard of for this to work is that somehow when under pressure the air bubbles are smaller so can find their way to the top. Convinced? No, neither am I.
01/01/2000 00:00:00 UTC
Stephen Latchford said :-
Thanks Ian seems you are the only one who gets it, the only thing that can happen ( when lever is tied) is that all the air bubbles collect in a 'queue' and when the lever is blipped they then find their way into the res.
of course riding the bike gives the system a jolt which would then liberate bubbles up into the res as well
01/01/2000 00:00:00 UTC
Ren - The Ed said :-
While I agree with both Stephen and Ian that LOGIC dictates pulling the lever back with a zip tie overnight is nonsense - empirical evidence shows the contrary in my experience. I have used this method several times to great effect.
I hate that. I am always arguing with Sharon regarding what logic dictates against her "experiences". Regrettably this is one of those times that while it makes no sense I can only call on my practical experiences.
01/01/2000 00:00:00 UTC
SL said :-
Nope not having it
01/01/2000 00:00:00 UTC
Ren - The Ed said :-
He he!! It is what it is.
01/01/2000 00:00:00 UTC
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