Sticking disk brakes in the mornings (and evenings...)

rat_race

Hi,

Recently, my brake pads seem to be really stuck every morning, and I don't know why. Also, it seems to be AFTER I've pumped the brakes once or twice...it hasn't been left like that from the evening before: the bike is okay until the brakes are used. It takes about 20 minutes of riding before they stop, and it feels fairly normal again. By the end of the ride, it's usually 100% grand again.

They can initially rub so much that it's nearly impossible to move the bike manually.

Some background:

Since I bought my second hand (2010 Ninja) bike, I've always noticed there is some brake pad rub. Even up up on a stand, neither front nor back wheel will do a full rotation if I yank it by hand. Not ideal, but I'm guessing it's common-ish.

It was rare that it got bad though, and I often never noticed. But recently, I reckon the cold might be a factor. I'm not sure. I didn't really notice it this bad last Winter.

Also, when I changed the pads 5 months ago, one thing I noticed was the pistons were pretty dirty. Small dots of cement-like dirt on them in places. And I cleaned as much as I could BUT, in the end I had no brake cleaner so they're still a bit dirty. But nothing too bad.


Any ideas why this is happening? It could possibly be too much fluid, as I had a mechanic top the fluid up when I had <1mm of pad left. Then I replaced the pads (and had to let a small bit of fluid out to get the pistons back). BUT, as the brakes worked reasonably okay up until now, I can't see the fluid levels being responsible. Thoughts?


Cheers,
rat_race

blu3r0ri0n

I use to have the same issue on my Dragstar, the pistons were getting corroded, once cleaned and greased they didn’t get stuck again.

Wossack

yea, calipers need to be rebuilt (complete, with new seals) by the sounds of it

bladespin

More than likely it's crud on the pistons stopping them retracting, what weight was the brake fluid you used?

rat_race

Wossack wrote: »

yea, calipers need to be rebuilt (complete, with new seals) by the sounds of it

I'd hope not to have to go that far. Probably be cheaper to buy new calipers as a whole...?

bladespin wrote: »

More than likely it's crud on the pistons stopping them retracting, what weight was the brake fluid you used?

But they do retract after a while, which is odd...but it just takes a few mins of riding. That, OR the I'm wearing a layer off the pads every morning. After 30 mins of riding, if I stop, and pump them, then release, then they are fine. But left overnight, something happens.

I reckon I will figure out how to bleed, then go clean the calipers and pistons, and re-bleed. If still giving issues, I'll buy new ones (or rebuild). It's my only mode of transport right now though, so it'll take some planning

No idea what brake fluid, but I presume dot 4. I haven't replaced or topped it up yet (service topped it up this time last year)...

rat_race

I'm going to rebuild front and back brakes (clean, new seals, change fluid)...anyone know where I can buy seals online?

Also, to clean, I presume any standard brake cleaner will do?

I presume I don't need any special tools??? I have torque wrenches, and can find some suitable 3/16" pipe handy enough I'm sure.

Please Kill Me

rat_race wrote: »

I'm going to rebuild front and back brakes (clean, new seals, change fluid)...anyone know where I can buy seals online?

Not 100% sure, but try places like Horsepower or Demon Tweeks or even Ebay. I came across seal kits there the other day when I was looking for something else.

rat_race wrote: »

Also, to clean, I presume any standard brake cleaner will do?

Yeah pretty much. If you're going to get some, the Muc-Off brake cleaner is pretty good, I've used it myself a few times. The Putoline is good stuff too.

rat_race wrote: »

I presume I don't need any special tools??? I have torque wrenches, and can find some suitable 3/16" pipe handy enough I'm sure.

Nope, once you have the basic tools and/or a decent socket set, you'll be grand.

rat_race

Please Kill Me wrote: »

Not 100% sure, but try places like Horsepower or Demon Tweeks or even Ebay. I came across seal kits there the other day when I was looking for something else.



Yeah pretty much. If you're going to get some, the Muc-Off brake cleaner is pretty good, I've used it myself a few times. The Putoline is good stuff too.



Nope, once you have the basic tools and/or a decent socket set, you'll be grand.

Thanks, PKM!

Xios

Might i suggest that it could be water in the brake fluid, which is expanding/contracting with the temperature?

rat_race

Xios wrote: »

Might i suggest that it could be water in the brake fluid, which is expanding/contracting with the temperature?

Something like that seems more likely to me, but I can't be sure?...It seems to stop sticking after driving the bike for a while...and the cold does seem to affect it.

I've noticed it's only the back brake. I think a rebuild will be fun anyway...

Cienciano

Put grease on the discs.








don't

Wonda-Boy

When was the last time the brake fluid was changed?

rat_race

Wonda-Boy wrote: »

When was the last time the brake fluid was changed?

Never. Bike reg'd April 2010, so not too old.

Wossack

Try wemoto.com for parts

Red rubber grease is oft recommended for the seals, but I've never used it (jut cause ive only seen it for sale in huge industrial tubs of the stuff- more then I'd use for a thousand rebuilds )

rat_race

Wossack wrote: »

Try wemoto.com for parts

Red rubber grease is oft recommended for the seals, but I've never used it (jut cause ive only seen it for sale in huge industrial tubs of the stuff- more then I'd use for a thousand rebuilds )

Thanks! Have been quoted 54e for the 8 seals (4 back, 4 front), from a well known Irish Kawsaki dealer. Bit steep for some pieces of rubber...is that fairly typical?

Wonda-Boy

rat_race wrote: »

Never. Bike reg'd April 2010, so not too old.

Is it not recommended that the fluid be replaced every 2 yrs for optimal performance?

rat_race

Wonda-Boy wrote: »

Is it not recommended that the fluid be replaced every 2 yrs for optimal performance?

Haha, you're really giving me a hard time today!!!

Yes it is...and I will replace it soon...but it is unlikely to be the problem, I reckon?

Given the dirt I remember seeing on the pistons before, I think a rebuild is a good idea (any excuse to try something new)...

Fr Dougal

Have you tried the simplest things first? Simply doing a proper clean of the calipers/pistons might fix the problem? When were they last cleaned? I clean mine every couple of months cos bike is in everyday use.

I would have expected dodgy seals to cause leaks or spongy brakes, rather than hard brakes
EDIT: Just re-read your first post, they were last cleaned 5 months ago. Deffo try cleaning them first. Squeeze out the pots a couple of mm. Use Wd40 and strips of old denim to clean behind the pots. This will help remove the cement like dots. Then wipe off all traces of Wd40 before replacing pads. You could also get a tool to turn the pots, don't use pliers as this will damage the surfaces.

Google how to clean motorcycle calipers, there are loads of links with fotos. I would post links for you but on mobile at the moment

rat_race

Fr Dougal wrote: »

Have you tried the simplest things first? Simply doing a proper clean of the calipers/pistons might fix the problem? When were they last cleaned? I clean mine every couple of months cos bike is in everyday use.

I would have expected dodgy seals to cause leaks or spongy brakes, rather than hard brakes
EDIT: Just re-read your first post, they were last cleaned 5 months ago. Deffo try cleaning them first. Squeeze out the pots a couple of mm. Use Wd40 and strips of old denim to clean behind the pots. This will help remove the cement like dots. Then wipe off all traces of Wd40 before replacing pads. You could also get a tool to turn the pots, don't use pliers as this will damage the surfaces.

Google how to clean motorcycle calipers, there are loads of links with fotos. I would post links for you but on mobile at the moment

Yeah, I think I'll not bother with the seals just yet. I really do think this is temperature related. The colder the day, the bigger the problem. Warmer days and there doesn't seem to be any issue...

I will try to clean them (I presume when you say pots you're referring to pistons). I will replace the fluid too while I'm at it...

I'd like to take the pistons out, but won't that let fluid leak? Or is it somehow a closed system?

Fr Dougal

rat_race wrote: »

I will try to clean them (I presume when you say pots you're referring to pistons). I will replace the fluid too while I'm at it...

I'd like to take the pistons out, but won't that let fluid leak? Or is it somehow a closed system?

Yeah, pots are the pistons. Don't take the pistons out cos they will let the fluid out.
It is not a closed system. Just gently press the pedal until the pistons come out a couple of mm only.

rat_race

Fr Dougal wrote: »

Yeah, pots are the pistons. Don't take the pistons out cos they will let the fluid out.
It is not a closed system. Just gently press the pedal until the pistons come out a couple of mm only.

Thanks...though, I was hoping to take them out and clean the pistons properly and inside the caliper.

Before, when I noticed dirt on the pistons while putting in new pads, I failed to clean completely (though, I did try), and also used a small plastic clamp thingy to push them back inside the caliper as they were very stubborn. So I wouldn't be surpised if there was some dirt in there ...