Is my front brake piston seized?

[macca__macca]

Hi all,

Recently I noticed my front right brake rotor was cool after riding, and the front left was very hot. This indicated my front right pistons were not 'pushing' out properly when braking and sure enough when I pulled it off the bike two of the pistons were very stiff. I managed to clean them up and make them move more freely, so they are not seized in the sense of being unable to move in or out of the caliper.

However, after riding the bike again I still find that the front right rotor is only warm, and the front left is very warm-to-hot.

What is normal? When you guys get off the bike and put your fingers on your front rotors, are they both the same temperature, and both pretty hot?

Before I go pulling everything apart again I just want to validate what is within the scope of 'normal'.

Thanks all!

[lloydie]

Time to strip and clean them up .
Or send them off to jonesy so he can get his hands dirty , he does a great job at servicing brakes .oh not for free tho .

[agentpineapple]

Time to strip and clean them up .
Or send them off to jonesy so he can get his hands dirty , he does a great job at servicing brakes .oh not for free tho .

+1 for Jonesy, give him a shout, he's a top man and very reasonable. he's looked at all my front calipers over the last few years...

[tony.mon]

Sticky pistons are often the hottest side.
This is because the pistons are pushed onto the disc by quite a lot of hydraulic pressure- they'd have to be bloody welded in to resist that- but the problem is usually that they don't then retract a fraction of a mm to release the disc. They therefore continue to grip the disc, making it run hotter than the other one.

It will be the hot one that' needs stripping and cleaning, often all that's needed is to pump the pistons out, clean and then red rubber grease around the seal and push back in. repeat a few times, and they are nice and smooth again.

But Jonesy is a big recommend, if you're not sure he does a cracking job.

[MacV2]

Yep whip 'em off & send them to Jonesey...

The Master Braker...

[Jonesey]

b

[macca__macca]

Well I don't actually live in the UK anymore, so can't send them to Jonesy, however I did take apart the 'hot' caliper and pulled the pistons. Sure enough they were almost impossible to remove even under the pressure of the brake system! Had to get some pliers on them with some rubber to protect the pots themselves.

I have ordered new seals as the old ones were definitely uneven in shape and need replacing. I will do both calipers.

Thanks all for the help.

Macca

Sent from my LG-H815 using Tapatalk

[tony.mon]

Well I don't actually live in the UK anymore, so can't send them to Jonesy, however I did take apart the 'hot' caliper and pulled the pistons. Sure enough they were almost impossible to remove even under the pressure of the brake system! Had to get some pliers on them with some rubber to protect the pots themselves.

I have ordered new seals as the old ones were definitely uneven in shape and need replacing. I will do both calipers.

Thanks all for the help.

Macca

Sent from my LG-H815 using Tapatalk

Newsflash!
International postage now available in most countries!

It's about time Jonesy started doing an exchange service, with a deposit in case your exchange ones are knackered.

[Jonesey]

Yep that sounds like a great idea, I'm all for it
If people are interested, or not- I'm glad to help if I can.
CJ

[macca__macca]

Ok so I've overhauled both calipers, replaced all seals, polished the pistons and they seem to be much better; I no longer have a hot disc and no binding :-)

However, I now notice that every now and again when I pull my front brake lever it's very stiff and I get no brake power for a moment - it's like the lever can't be pulled in! If I release and then try again it's usually fine and the braking is strong. This happens about 1 in every 15 times I use the lever.

I got home and re-bled the system again and just kept bleeding until it did it again during the bleed!? It happened just as I was pulling the lever in and cracking the bleed nipple - so it occurred at a time where there was no pressure in the system as such and I definitely should have easily been able to pull in the lever as I opened the nipple.

What could this be? it's not air - I bled the system really carefully several times and there's no air in it that I can tell, but I don't know what else could explain it? Could my master cylinder somehow be jamming up all of a sudden? I've never had the issue before and it seems very coincidental that it's happened only now after I've totally overhauled both calipers...

Macca

[fabiostar]

if it was stiff to pull without any pressure id be looking at the other end of the system. time to check the master.

[agentpineapple]

JONESY!!!!!!!!!!!!!