Locking Right Front Wheel

[fjmuurling]

Hello,

When I brake hard my right front wheel locks up (Only that one) The car is a LHD 1990 SE with the TMC front brakes and has EBC Greenstuff pads. When braking normal all is right ie the car doesn't pull to one side. Any idea's as what is causing this and which one is the most likely one. The calipers are free and not sticking on the sliding pin. The right hand front disc has some dark spots which are equally spaced around the circumfence of the disc. I don't know if this is the cause of the problem or if this is the result of locking up the wheel. Furthermore all the brake hoses are of the stainless steel braided type and the brake fluid is fresh. Any idea's are welcome.

Freek

[Glyn Harper]

Could be a little bit of air in the left hand pipe maybe? Or if one of the handbrake calipers at the back is ceizing slightly, it would upset the weight balance on braking which would cause this.

I assume you've checked the first obvious thing.. tyre pressures?

If one tyre pressure is lower than the other, it'll unbalance braking noticably as the flatter tyre has more grip under braking as more of it's surface area is in contact with the road.

[Esprit Aviation]

I would have to agree w/ Glyn about the tire pressures. I also wonder if it may be due to a lack of weight on that side. Since there is no side to side brake biasing.

Lee

[CNH]

Did you recently change pads?

Sometimes as the old pads wear it exposes the caliper piston which pits or experiences corrosion spots. When new pads are installed this piston area is retracted back into the caliper that may stick. I have heard of such occurrences when the car is not used often and has long intervals between pad replacements as the piston is exposed for long periods.

The dark spots are most likely caused from high temps by hard or prolonged braking.

They can be caused by the pad material being imbedded into the disc surface during high heat. I would probably be looking at a sticking piston if I were in your situation.

Calvin

Edited April 17, 2007 by CNH

[fjmuurling]

The pads were changed 2 years / 7000 km's ago and are still in good shape. The handbrake cables are also new and the tire/tyre pressure is 2.1 bar all around and I check the pressure very regularly (almost every time if I take the car out if the car was sitting still for more than 2 weeks ar so). This is not a recent problem, I had it in the past also a few times but 2 days ago I had to brake hard in order to avoid a crazy volvo v70 driver who thought he could drive on the wrong side of the road.

The brake system is airfree.

I hope somebody has some more idea's, next week I'm going to check on the caliper but from memory when i changed the pads they were all ok.

Freek

Edited April 17, 2007 by fjmuurling

[CNH]

Does the pad stick on pedal lift off?

The calipers also will float with no load but if they are dry and the grease hardened up they may stick under load. Lube both the float pin and with the pads out have a friend slowly press the pedal. This will extend the piston from the caliper. Use caliper grease and apply to the piston. You will have to gently pull the boot out of the way, do not rip it. After you have lubed the piston use a C clamp to retract the piston. Hopefully that will help. Use high temp synthetic grease made for brakes or the grease will dry out and cause sticking.

Edited April 17, 2007 by CNH