Breaks Binding.

[Pete Mar]

Morning all,

 

Managed to get the old girl out for her first proper outing at the weekend and I noticed that the breaks seem to be binding front and rear to the point that they will hold the car on a slight hill, this seems to get worce when warm. I have drum rear breaks and the fronts are 4 pot Wilwood callipers on unvented discs, all brand new.

 

I have tried the following:

 

1. Adjusting the break peddle so that there is plenty of space between the peddle stop and the rod bushing the piston in the master cylinder so this is not putting pressure on the system.

2.I have adjusted the rears to make sure these are not tying up on the auto adjusters.

3.I have also measured the callipers to make sure they are centred on the disc and they are

 

The breaks work fine and pull the car up very well, just seem to have these binding issues.

 

Anyone come across this before?

 

Cheer

Pete

Edited April 14, 2014 by Pete Mar

[Guest Ian & Carole]

Even though you say you have plenty of space around the brake pedal / push rod are you sure that the brake master cylinder piston is returning to its stop in the cylinder.

 

If it isn't returning it will mean that the brake fluid is under pressure and keep the brakes on slightly.

 

I am of course assuming that you have checked for seized calliper pistons and rear brake cylinders.

[Pete Mar]

Hi Ian,

 

Not sure on the master cyclinder piston, I will take a look later tonight, I did take the calipers off and they seemed fine. I did push them out and give them a little wipe over with copper grease just to be sure though.

 

Cheers

Pete

[Guest Ian & Carole]

Just another thought on this, jack up and check for binding brakes and just crack open the bleed nipples with a bit of cloth over the end if it is the master cylinder not returning, when you crack open the nipple you might get a little squirt of fluid and the wheel should then rotate freely.

 

Having done this apply the brakes again and see if you get binding again.

Crack open the nipple and see if you get fluid release under pressure and then free spinning wheels will confirm the brake master cylinder is your problem.

[richyb66]

How are your brake light actuated, pressure switch or a switch directly on the pedal. If it's a pressure switch and the brake lights aren't on all the time, then the problem isn't residual pressure in the system.

[Pete Mar]

I have the pressure switch and the lights are not stuck on so I guess that means it is not pressure in the system. I am going to have to take a real close look at the calipers and the pads I guess,all seemed to be inline though.

 

Cheers

Pete

[richyb66]

Jack up each corner and see which wheel is/are binding to try and elinimate a few other possible causes.

[Guest zoomzoom]

Hi, I had the same problem with my zero on its first run (to sva)

The front brakes where locked solid when I arrived for the test. but as the car cooled down they unlocked.

It was the heat expansion in the pedal box pressing the pedal and pressuring the system, so a little clearance soon sorted it out.

 

You will just have to check which wheel of wheels is binding by jacking up when the problem happens

might be a kinked hose on one of the front calipers holding pressure on the side or of course some thing else........

good luck

[Pete Mar]

Cheers for the feedback gents. Given me a few more bits to look at.

 

Pete

[Longboarder]

Can I add my support for jacking the car up corner by corner and trying to turn each wheel. This will identify which wheel has the problem. Then it's simply a question of investigating one wheels components. If it's all four wheels then it has to be a component common to all four wheels. The only component common to all four wheels is the brake master cylinder. Regardless of what you think the brake light pressure switch is telling you. (Don't assume the brake light switch is working at 2psi. It might be sticky and only working above 15psi or some figure that applies some braking.)

The master cylinder piston must be able to fully return to its stop when you take your foot off the pedal. (This is not the same as the pedal returning to it's stop. There must be free play between the pedal and the operating rod.) The last 2mm of travel open the hole to the brake fluid reservoir allowing heated/ expanded fluid to escape back out of the lines or new fluid to enter the cylinder if needed. If you loose those last 2mm of travel the system is effectively sealed and any fluid expansion will apply all four brakes.

Also ease off the handbrake adjuster and rear wheel adjusters and allow the rears to self adjust on the pedal only. Then take up the handbrake slack. Too many people adjust up the handbrake to take up slack in the rear brakes.

 

Nigel

Edited April 15, 2014 by Longboarder