Front brakes binding

[olr159w]

See here first : viewtopic.php?f=4&t=32294

So I took the Sprint out for a test drive and the main issues experienced as a driver were the vibration noise and the general long standing state of the steering play.

But there was also some occasional high pitched squealing, definitely wheel related. When I got back I check the wheels - rears fine, fronts hot.

The wheels are now off and if you spin the hubs the brake pads are gently but noticeably binding. In doing the rear brakes per axle oil leak I also replaced the rear brakes pads and cylinders and refitted the Goodrich braided hoses that the car had when it came to Australia. They didn't pass the regs here because no one had ever heard of them.....

So stock cheapies went on and the Goodrich ones sat in a bag for 13 years or something before getting swapped back on per above. All bled and all seemed fine.

Now the brakes bind. I have to be honest - I don't understand why disc brakes release anyway. What makes them bring the pad back off the discs?

And what could be the cause? Might the braided ones have deteriorated in the bag causing that inner lining one way valve problem I've read about? Or would people more suspect the caliper seals?

Thanks

[Jon Tilson]

Take the pads out and see how hard it is to push the pistons back in. If they dont slip back quite easilly then you have sticking pistons.
I have never known a goodridge hose do the one way valve thing. The rubber hoses do that all the time...

The pads get knocked back off the disc pretty easily if the pistons are free, so don't bind.

Jonners

[olr159w]

OK. And caliper overhaul kit and rebuild etc if they are sticking? ie there's no way of resolving this without going that route?

thanks

[tony g]

While in the binding state, undo the bleed nipple and see if the caliper goes free. If so the hose or pipe is restricting flow. If nothing changes, tighten nipple and proceed to push the pistons back and pump them back out (with pads in) and it might free off enough to stop binding.
Pistons release tension because of the seal structure and shape. When pressure is applied they swell into the bores and when released they retract back a tiny amount which releases the grip.

Tony

[Richard the old one]

When I check my cars over prior to their MoT's I do the following.

I have kept a set of well worn pads which I fit loosely and then operate the brakes to push the pistons out as far as possible. I then push the piston back in again. I do this several times and it does seem to help to keep the piston free over their complete travel.

[olr159w]

I just checked the NS caliper. Pressing with both thumbs I can't move either of the pistons. Bearing in mind they've sat still and the last overhaul was probably 2002 I think I can safely say it's time to revisit.

I think we'll consider this question resolved particularly given Jonners positive words about Goodrich braided pipes not being known to collapse.

thks

[tony g]

I doubt they would move much with thumb pressure tbh. Did you undo the bleed nipple and try it?
Tony

[MIG Wielder]

How about fitting stainless steel pistons from Canley Classics.
I think the Dolomite callipers are "Type 14 " Is that right please ?
I fitted them on my daily driver 1850 as they corroded due to salt in the winter.
Quite expensive at about £60 a set.
Tony.

[olr159w]

I just tried the NS caliper with the bleed nipple undone. It made no difference at all.

Clearly they are partly seized and it's time to re-do the front brakes.

[Jon Tilson]

I agree about thumbs unless yours are strong and you can push in a non sticking caliper.
I always use a large flat screwdriver and an old worn pad to get an even push...You can skew the piston if you just push on
the edge and that will make it stick.

Push the pistons out one at a time with the brake pedal.

I tend to fit new pistons too as at 12-15 quid each its kinda false economy not to.

Jonners

[SprintMWU773V]

I resisted buying a piston wind back tool for years and eventually bought one for a tenner or so. It consists of 2 paddles and a screwed shaft. You simply put the paddles between the pistons and wind away. Best £10 I've spent and made the job much easier having battled for years with G clamps, bits of wood, screwdrivers and such like.

Looks like this https://goo.gl/images/cJtEWB

[olr159w]

I reckon my thumbs are strong enough but there was no movement even with the bleed nipple undone.

I guess I could try it with a pad and some leverage but these seals haven't been changed in probably 14 years and the car has had limited use. It's time.

Why should the pistons really need replacing? You are going to say corrosion right?

[grahamwatson]

Yes. They tend to corrode in the area under the rubber dust cap, and that can become the critical sealing area when new thicker pads are fitted.

[xvivalve]

I don't know what carriage to Australia would be (I've successfully sent stuff to NZ with international economy rate), but the fully reconditioned callipers the club supply are very competitive at £40 each; less than the sum of the parts if you do them yourself!

[olr159w]

That is a good price although shipping whole calipers would be a lot more than just the overhaul kits !!

Do these calipers have stainless pistons too?

thks