Arghh!! Piston Lube, can you, can't you?

[flamegrape]

A short time back I posted about one of my pistons refusing to tow the line and work with the others to push my pads!!

I followed everybody's advice and removed the calliper, cleaned everything up and (short of rebuilding the damn thing - which I'm manly enough to admit... I'm afraid of doing!!) got all my pistons dancing in time.

Now the same one is playing up again. If this little sh*t was only pushing the brake pads as much as it pushes it's luck I would not be trawling the net for a solution, only to find so many differences in opinion!

Anyway, my question is, I think I can fix my problem (without stripping the calliper) with some cleaning and lubrication. I've read WD40 is a suitable light oil to lube the pistons, others say brake fluid, others say red grease , others say to use brake grease and NEVER to use Copper Grease.

Can anybody suggest a solution/lubrication method to help? This is not a huge problem (despite my hysterical outburst!) and not causing a load of bother (but I can hear the pad brushing the disk when when riding) but I don't like riding knowing there is something which needs fixing because that means something isn't working right!

Any help and advice would be greatly appreciated!!

Thank you.
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Jonny (Riding his Kawasaki ZX6R J1)
It's one big learning curve right now

[.....]

Don't put WD40 on your brake pistons. It sounds like you really do need to pop the pistons out and clean behind the seals and probably put new seals in. It's actually a quite straightforward job. When putting the seals and pistons back in lube them with brake fluid.

[flamegrape]

[Frost]

Brake fluid is piston lube. Make sure you soak the seals in it and put some on the piston before you put it back in.

[0l0dom0l0]

stripping the calipers, and replacing the seals is easy. if you want to do it in an afternoon, order the new parts before. wemoto do a kit i think, it will be around £30, and i can tell you thats proably the cheapest you will find.

just pop all the pistons out, and give everything a darn good clean. where abouts are you located? if you near me, i dont mind giving a helping hand!

[LongJohn22]

In your original thread, you said the pad was rubbing against the disc. If this is your only problem, you simply don't have a problem. All disc brakes operate in the same way. There are no return springs, so nothing to lift the pad off the disc. The only time it becomes a problem is when a fault develops that causes the brakes to bind, which will become apparent when you suffer a loss of power and the brake disc heats up substantially.

[.....]

Don't the seals pull the piston back ever so slightly? Otherwise the brakes would bind all the time.

[flamegrape]

[0l0dom0l0]

[Frost]

Warning, a piston that doesn't retract and stays running on the disc, e.g seized, as they usually are, won't be blown out with a weak compressor and can't be pulled out by hand without destroying the piston.

Remove the pads with the calliper still on the bike. Place a screw driver where the disc would have been and pump the lever. Initially only 1 piston will move until it hits the screw driver and stops. Continued pumping will move out the other pistons until all are unseised and can be removed.

[0l0dom0l0]

[flamegrape]

Superb!!

I'll get onto YouTube and see what there - different people do things different ways - being new to it I'm always unsure who to follow for advice and which is good/bad advice.

I'll get this sorted ASAP and I'll drop a reply to this post and let you know how it went!!

Cheers guys!!
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Jonny (Riding his Kawasaki ZX6R J1)
It's one big learning curve right now

[flamegrape]

PS: Thanks 0l0dom0l0 for your kind offer!!
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Jonny (Riding his Kawasaki ZX6R J1)
It's one big learning curve right now

[Blue_SV650S]

Red rubber grease is the lube you are after.

So clean the gunk from behind the seals and re-assemble with red rubber grease, it is not only perfectly safe on brake seals, it is actually recommended to apply

https://morrisminorspares.co.uk/shop/images/graphics/LUB108.jpg
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The purpose of life is to fight maturity.

[evoboy]

Youll probably find youll need to remove the pistons and dust seals to stop it seizing.

I persissted with the 6pots on my j1 for nearly 2 years till i just stumped up the cash and bought a set of Nissin 4 pots off a 1200bandit.

Not only a stiffer lever and more reliable braking power, but they havent seized up on me yet!
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Suzuki GT250 x7------- Fazer 600------CB250RS------Aprilia Rally 70----- Bandit 600

APT Motorcycles

[TUG]

[Bull]

I got to do the same on my ER5 i got
As someones said go on www.wemoto.com i think its com and not co.uk)
Put in the make and model of your bike and your get a list of ALL the parts they do

My ER5 they do a Stainless Steel Piston and Seals (mine has 2 pistons one small one bigger and there both around £20/21 each I think that maybe Delivered aswell,

I still got to order mine when i get chance

O and sounds like your going to have to remove it Fully as i did the same as you tried doing it on the bike worked abit but still catching,
So that will mean Bleading the brakes ( i also hate brakes lol O and Red Grease is whot you want to put the pistion back in with and you can get a tube off Wemoto at the same time as the pistion and seals,

[stinkwheel]

[flamegrape]

If I remove a piston to clean and replace the seals - do I need to bleed the brakes and will there be a haemorrhage of brake fluid when I pop it out
____________________
Jonny (Riding his Kawasaki ZX6R J1)
It's one big learning curve right now

[D O G]

I'm a shit mechanic, and have rebuilt calipers before, and have three more to do soon.

Whilst in principle it isn't 'difficult', it's not, IMO, the pOp dom indicates. Getting pistons out can be a total bastard - there was a recent thread on here with a guide from some guy doing his TLR calipers. Well worth a read.

A good tip for getting annoying pistons out if you don't have a compressor, is to use a cycle pump - the big upright ones, and a high pressure valve from a road pushbike inner tube. You can cut the valve from the tube, trim the rubber so it screws tightly into the caliper thread, and pump the air in. If the 'other' piston is secured one sticky one should pop out.

If you manage to get them out easily (ho ho), then on reinstallation make sure that the seals are correctly orientated - some seals are tapered, put them in the wrong way round, and if you force the piston in - like I did, you're fucked, new seal time. They should press in with finger pressure.

Then you have to bleed the brakes. Which is not that easy, and I've heard that the 6 pots are particularly gruesome.

If I was doing this, and I had all the parts and tools available to me straight away, I reckon I could do it in a day. Maybe. Probably a whole weekend after all the messing about.

Just a word of reality from someone who has only done this once.

[Robby]

One bit to add on what everyone else has said. You're not scraping behind the seal to remove seal residue, you're scraping out alloy corrosion. Lots of loose white powder will come out when you scrape in there, keep scraping until no more white powder comes out.

[LongJohn22]

There appears to be a degree of confusion as to how a disc brake actually works. As I stated earlier the pads are in constant light contact with the disc because there is no mechanism to withdraw the piston after the brake lever has been released. The following has been lifted from an item on the web titled "How disc brakes work", it can be found at;
https://auto.howstuffworks.com/auto-parts/brakes/brake-types/disc-brake2.htm
As I also stated earlier, based on the information previously given by the OP, I am far from convinced that a problem exists, a binding brake will manifest itself in a significant loss of power and a disc literally too hot to handle.

The single-piston floating-caliper disc brake is self-centering and self-adjusting. The caliper is able to slide from side to side so it will move to the center each time the brakes are applied. Also, since there is no spring to pull the pads away from the disc, the pads always stay in light contact with the rotor (the rubber piston seal and any wobble in the rotor may actually pull the pads a small distance away from the rotor). This is important because the pistons in the brakes are much larger in diameter than the ones in the master cylinder. If the brake pistons retracted into their cylinders, it might take several applications of the brake pedal to pump enough fluid into the brake cylinder to engage the brake pads.

[0l0dom0l0]

[DrDonnyBrago]

[Blue_SV650S]