Front Bakes

[ftfo]

I have a problem with my front brakes binding. Its so bad it failed the MOT.
I have recently fitted new discs,pads,braided lines and master cylinder. After the bike failed its MOT I took a look at the calipers and found the left hand one was the problem. I got a good second hand one fitted it but the brakes are still binding. The only thing left to change is the 3 way splitter on the forks.
Any Ideas on what it could be or have any of you guys had a similar problem.
I'm pulling my hair out trying to sort it.
Cheers

 

[MattW]

Are you sure the pistons are sliding freely in the calipers?

BTW, people will need to know the model and year of your bike and whether it's ABS etc if they are going to be able to offer advice

 

[ianboydsnr]

how do you know its the left one, did they bind before you replaced the lines, master cylinder and pads,
when you loosen the caliper nipple and pull the lever does fluid come out, the master cylinder that you replaced, was it new,

do the pistons slide back easly, with or without the caliper bleed nipple opened,
does it bind on the full disc or just in parts,

have you had anything done which involves stripping the front end, what model bike is it?

I actually thought this thread was about baking

 

[DrFarkoff]

If the bike has been ridden in the winter "salts" find thier way in behind the wiper seals (and when really bad the main seals too) and jam the seals against the pistons not letting them fully release

Piston rubbers do swell too You can get kits for about £45 which have pistons and seals from motorworks, motobins or sherlocks

My master cylinder piston rubbers swelled up and it wasn't returning to the zero pressure position and was therefore always keeping the brake on a little the big clue was the lever had loads of free play and it got worse

There's no big problems with the brakes on these bikes except the servo ones which are a right pain in the arse! if you remove a calliper just seal the end with a bit of inner tube and a spring clamp to prevent fluid running thru

come back and let us know what the problem was

 

[ftfo]

The bike is a 1100 with ABS
Master cylinder is new. I know its the left hand caliper as I took it off put a piece of hard wood to hold the pads back and tried the brakes. The right hand one works fine. Did the same the other way round and the left one stays on. I have replaced that caliper with a new one but the problem is still there. So the only thing I can think of is the splitter on the forks. This is the only place that fluid could be prevented from being returned. I have bled and re bled the brakes. Put over a litre of fluid through. The binding is constant so I know the disc is not warped. I guess I'll just change the splitter and see what happens.
The discs I put on were not BMW ones. I have ridden the bike as is and the ABS works fine.
Any clues as it is driving me nuts.
As for the BAKES You probably could have cooked on them !!

 

[DrFarkoff]

IF you pump the pistons out can you push them back in with moderate pressure on that calliper?


Discs ???Ah Ha Not BMW ones ?

So if you refit the calliper is the disc running nearly at dead centre of the calliper?

If not then new pads could be constantly binding! Due to the offset

Try a thinner set (i.e. worn ones) and see if it still occurs

 

[ftfo]

Will be giving it another go later today. Let you know how I get on.

 

[ianboydsnr]

I dont see how it can bind at the splitter, only either the hoses or the caliper

 

[Steptoe]

I dont see how it can bind at the splitter, only either the hoses or the caliper

Same thought here - it'll be the lower flexable hose thats collapsed inside stopping the fluid returning on that caliper.

 

[ftfo]

The hoses are new braided ones. Thats the reason I changed them as I thought they may have collapsed inside!! Had that problem with a mini about 20 years ago. So I'm still stuck with binding brakes after renewing nearly the whole braking system. If I had any hair I'd pull it out

 

[Stewart H]

I think you need to get the pistons out of the caliper and clean them and the bores using a green pan scrubber and brake fluid, get the seals out and clean behind them too, reassemble using red rubber grease if you have it and brake fluid if you dont.
Stewart

 

[DrFarkoff]

The hoses are new braided ones. Thats the reason I changed them as I thought they may have collapsed inside!! Had that problem with a mini about 20 years ago. So I'm still stuck with binding brakes after renewing nearly the whole braking system. If I had any hair I'd pull it out

????????

Discs ???Ah Ha Not BMW ones ?

So if you refit the calliper is the disc running nearly at dead centre of the calliper?

If not then new pads could be constantly binding! Due to the offset

Try a thinner set (i.e. worn ones) and see if it still occurs

 

[Steptoe]

Is the front brake lever returning fully.

 

[ftfo]

Ok I've had a look at the disc and it runs just about centre. Give or take a fraction of a mill. So the pistons should be able to cope with that.
Also the lever has a good feel and returns to its outer most point no problem.
Didn't have time today but am going to take a look at the splitter. This may have some crap in it so not letting the fluid return from that side.
The old rubber hoses were pretty shite so may have degraded internally and caused a non return valve at the splitter.
Its my only hope!!
Will let you all know when do. Thanks for all the advice so far though.
FTFO

 

[ianboydsnr]

you could try back bleeding the troublesome caliper using a syringe, you'll know wether or not the issue is with either the master cylinder or lines, depending on wether or not you can back bleed them

 

[ftfo]

I Have got it sorted. A small piece of the old flexible brake line had got stuck in the 3 way splitter it was working like a valve. Letting fluid past but not back to the reservoir. Thanks for the input on this just glad its sorted. Can now go get an MOT.