How hot should inboard brake discs get?

[JohnWoodman]

I was driving to work today and got a wiff of hot brake pad. I had only been trundling along at 40 to 50 mph with very light use of the brakes. When I pulled over the rear discs I could not touch. They were hotter than the front discs so how hot should they be with this sort of driving?

I have also noticed a squeak after I have been driving for a few mins. The squeak goes away when the brake pedal is pressed.

Squeaking rear brakes

The above thread talks about putting copper grease on the back of the pads (ie the part of the pad that contacts the piston) what effect does this have? Is this to prevent squeaking from pad to piston face shearing action?

Brakes were fine at the SVA and this has only started happening in the last 100 miles (and I've done about 400 now). I guess the pads could be glazed so I'll remove them and rough them up with some wet and dry.

I originally assembled the pads onto the pins which they slide along without any copper grease, would it be advisable to grease them?

Thanks
John

[craggle]

Brakes do normally get a bit warm as the pad dosen't really get pulled back off the surface of the disc after releasing the pedal, Just the pressure behind them gets less.
Did you fit reconditioned calipers or the original ones straight off the donor car? It is possible for the pistons to stick or get stiff in the calipers.

One other thing is the handbrake pads could be rubbing. My new handbrake pads didn't fit the shape of the discs when first fitted and rubbed for a while. They have now bedded into the shape of the discs and no longer do it.

Copper grease on the back of the pads helps stop squealing by damping the vibration created in the pads. This is only really necessary though if the pads are plain steel backed. The EBC ones I use have a rubber pad on the back that does the same thing. I have never grease the retaining pins on my brakes.

Craig.

[JoMo]

Hi John, I had a similar problem last year with my inboard rears. I arrived at a friends house after a 30 mile drive with smoking rears. I found that one piston on each side was sticking slightly causing the pad to rub slightly. Strip down, clean out, new pads( copper slip on back of pads and the edges where the pad backing slides on the caliper, I never put anything on the pins.) no problems since. Oh yes, they do squeak when they rub!

John

[craggle]

One other thing is to ensure the pedal is fully returning and not being held down by anything.
Try jacking a wheel up and spinning it round then pump the pedal a few times and spin it again. If it is tighter or impossible to turn the second time you may have a pedal or master cylinder problem.

My sisters Peugeot had a brake light switch stick and it held the pedal down a few millimeters from the stop. Every time she pressed the pedal pressure was building up and not being released. She managed to drive about 20 miles with the brakes hard on! All new discs and pads were required and now the CV boots, Steering joint boots and wheel bearing seals are failing. Guess they got a bit hot too!

Craig.

[slogger]

.............I had a set of Mintex rear pads that jammed in the calliper so they were rubbing. I cleaned the paint from the edge of the pads and the calliper. Very very thin film of copper slip on the back and edge of the pads and all was well.

The hand brake pads are another problem if not set correctly.

[JohnWoodman]

Calipers were re-conditioned from Ward engineering. I'll take the pads out this weekend and have a look. Dax tunnel is removable, but not really once it is covered in carpet. So it looks like an evening on the floor under the car.

Cheers
John

[slogger]

Originally Posted by JohnWoodman

Calipers were re-conditioned from Ward engineering. I'll take the pads out this weekend and have a look. Dax tunnel is removable, but not really once it is covered in carpet. So it looks like an evening on the floor under the car.

Cheers
John

My carpet is held down with poppers. That way it can be removed then clipped back in seconds. Must admit on my Dax version you need to strip the interior, seats and all and drain the water to get the tunnel out!!

[JohnWoodman]

Took pads out, all looks ok. De-glazed the surfaces and re-assembled with copper grease on the backs and edges of the pad mounting plate. Squeak has now gone, discs are still approximately the same temperature. Checking after a run showed that the discs were hot but there does not seem to be any heat transfer to the diff, drive shaft or calipers. All of these assemblies were no more than warm. So I'm thinking everything is fine, maybe I'll look into making a duct to force some air over the discs.

One thing to point out to builders, make sure you get the pins that retain the pads in such a way that they can be removed without having to remove the caliper. On mine I found I could not extract the pins because they fouled the chassis rail. There is one pin however that will foul the chassis in one direction and the diff case in the other direction. What have others done about this pin?

Cheers
John