rear brakes - Printable Version

rear brakes - Printable Version

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+--- Thread: rear brakes (/showthread.php?tid=61545)

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rear brakes - gordon - 18-01-13

failed mot on back disc being cracked x5,brake pad worn on right side and piston not working on left side,

is there any easy way of doing the piston lads ?

8 months on the road since i got it cant belive that the disc has cracked 5 times in that time and not picked up on last mot .

any help would not go a miss as i,m new to biking

Re: rear brakes - Dead Eye - 18-01-13

I guess it depends on what's caused the piston to seize? Could just need a good clean and re-greasing which should be easy enough.

Re: rear brakes - His Dudeness - 18-01-13

well you'll need a new disk obviously. you can go for an OEM one from a yamaha dealer or a cheaper ebay jobbie. the pistons are probably sticking in the caliper because the seals need to be replaced. you get a bit of corrosion in the recess behind where the seals are located and that pushes the seals out a bit and causes the piston to stick. i'd always go for OEM seals because you're guaranteed a perfect fit with OEM ones whereas copies tend to be a bit hit and miss. you'll also need a bottle of brake fluid and some rubber grease.

replacing the seals is not too difficult. getting the stuck pistons out is probably the hardest part. you have to make sure that the two pistons come out evenly and if one is stuck you'll have to clamp the one that is moving with a c clamp and keep pumping until the stuck piston frees itself. then reverse the clamp and pump the other so that the two come out evenly. you might have to add a little fluid as you pump them out. once they're out its just clean everything, add a bit of rubber grease to the seals and pistons and then push the pistons back in with the c clamp. then bleed some new fluid through. that can be easy or a right pain

Re: rear brakes - darrsi - 18-01-13

Rear's a damn site easier than the front 2 to sort out!

Re: rear brakes - darrsi - 18-01-13

@His Dudeness
Pistons?
There's only one?

Re: rear brakes - Dead Eye - 18-01-13

(18-01-13, 11:40 PM)darrsi link Wrote: @His Dudeness
Pistons?
There's only one?

Pretty sure there is one on either side of the caliper? Unless I'm thinking if something else? Gordon did mention it was the left piston which implies there is a right one as well Tongue

Re: rear brakes - wezdavo - 18-01-13

(18-01-13, 11:40 PM)darrsi link Wrote: @His Dudeness
Pistons?
There's only one?

Re: rear brakes - darrsi - 19-01-13

Sorry, me being daft, 2x pads, pushed from either side!!
DOH!!!
I was being nosey IN THE PUB, my bad

Re: rear brakes - His Dudeness - 19-01-13

(18-01-13, 11:52 PM)wezdavo link Wrote: [quote author=darrsi link=topic=5917.msg52588#msg52588 date=1358548819]
@His Dudeness
Pistons?
There's only one?

One?

No two!

I pull them out with a purpose made tool that grips the inside of the piston, you just give them a twist as you pull and they pop straight out.

Just clean and regrease with red rubber grease..

Never had to replace seals, even with a badly seized ones..

Done some a few weeks back, halved the caliper to make things easier..
[/quote]

he might get lucky and not need them. mine definitely needed to be replaced. i had another yamaha with the same problem but it was the front caliper and it needed new ones that time too but maybe i was just unlucky with them. thar definitely be two pistons in the rear unless someone's pinched one of them!

Re: rear brakes - wezdavo - 19-01-13

If you have to get the bike straight back on the road its best to have a set of seals ready to pop in, which in this case i would replace them as a matter of course..

When i last done them the bike was laid up anyway so if i needed to or order some it was no biggy, but as luck would have it they were fine, but if you need the bike for work dont rely on lady luck!!

Re: rear brakes - darrsi - 19-01-13

I was in the pub, with a new phone, trying to do my worst!
Apologies, i got so close to giving a good answer and then some numpty nudged me as well, i wasn't happy and gave up! :lol
Just got in now, messy night! :b

Re: rear brakes - gordon - 19-01-13

thanks lads, sounds like its going to be fun or not . if one pad is gone down a lot more than the other one surly that means that the piston is ok on that side ?

where as the other side is ok so its that one is stuck etc ? am i right in saying that
will let you know it goes when parts get here

Re: rear brakes - stevierst - 19-01-13

Replaced the caliper on one of my fzs600's as it was completely knackered when I got it and totally beyond repair. My current one has a sticky piston, and the seal is making the piston jam on, causing brake drag. Seals are only a few £, so its worth replacing them whilst you have the caliper off.

Re: rear brakes - gordon - 19-01-13

parts not turned up today, all took apart ready only one piston wont come out at all
off work on monday now as need it for work

Re: rear brakes - His Dudeness - 19-01-13

did clamp the piston that was moving freely? your options are

1.put the piston that came out back in and refill and bleed the caliper, then clamp the piston that's moving and pump until the stuck piston comes out.

2. split the two sides of the caliper and get the piston removal tool that wezdavo mentioned

3. if you have a compressor you can use a blast of compressed air to pop the piston out. put a piece of wood or something behind the piston because they can fly out and damage the piston or hit you!

Re: rear brakes - gordon - 20-01-13

back brake all ready for new bits on monday, the only thing is i cant undo the disc bolts any one know what
size the hex key is ( allan key ) ? or how to undo them easy ?

Re: rear brakes - Dead Eye - 20-01-13

I've been told that they are particularly stubborn and can be prone to rounding off the head so be careful - not sure on size though, sorry Sad

Re: rear brakes - packie - 20-01-13

(20-01-13, 12:16 AM)gordon link Wrote: back brake all ready for new bits on monday, the only thing is i cant undo the disc bolts any one know what
size the hex key is ( allan key ) ? or how to undo them easy ?

The previous owner (or factory) could have used thread glue so be careful. The best way forward is make sure you have a good hex bit (I think its a 6mm) from a socket set, but mount it on an impact screwdriver to shock them open. Maybe ever a socket wrench might be good enough. You will certainly have more leverage over a hex key. As mentioned, be careful not to round the screw or you'll be in deeper sh*t. If it's not coming, dont try to force it. Get the proper tool like an impact screwdriver or take the wheel to some mechanic who has one. Best of Luck.

Re: rear brakes - markbubble - 20-01-13

yea as already mentioned use a good quality bit in an impact driver or take to a garage to do as once rounded off there a real pain,it might also help getting some heat from a blowtourch or similar onto each bolt before you try loosen it to try and soften the locktight,if in doubt leave it to a garage to do

Re: rear brakes - Fazerider - 20-01-13

I found them extremely reluctant to undo when I changed my disc last year. The threadlock Yamaha use seems to get stronger with age. Front discs I never had much problem with, but the mileage I do means those get replaced every 3 or 4 years... the bolts on the back disc hadn't been touched in 13 and wanted to stay put.
I tried a gentler heat than a blowtorch at first, propped the whole thing up a foot above a small ring on the gas hob and after 20 minutes or so it was just getting too hot to touch. All but two of the bolts came out fairly easily then with an extension on the allen key.
Those last two needed less subtle treatment... I ended up welding a length of scrap steel to the remains of the heads. Massive leverage and the more extreme heat did the trick.