MG-Cars.net

Welcome to our resource for MG Car Information.

Recommendations

Parts

MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG MGB Technical - Brake knocking

I have a problem that is really starting to annoy me and I'm hoping someone can help shed some light on the situation. Last summer I completed a full rebuild of my car, and that included the brake system. I rebuilt both front calipers, replaced the pads, rotors, brake hoses, and the master cylinder. Whenever I lightly press the brake pedal there is a knocking noise coming from the right front wheel. The speed of the knocking noise is directly proportionate to the speed of the car, and slows as the car slows, additionally there is a bit of a surge feeling when I press the brake pedal. The master cylinder is NOT loosing any fluid, and I know the pistons inside the caliper are both facing the correct direction. (The depression in the piston lip facing the mounting bolts) My suspicion is a bad rotor, but I would like some other opinions before I start tearing things apart.

Thanks in advance,
Justin
Justin

Justin;
I would agree with your diagnosis.The fact that you are experiencing surge suggests a warped rotor. If you have a magnetic base dial indicator settup, you could check runout.Max runnout is given as .006" in Haynes,which seems like a lot.
Also check how your pads are contacting the rotors. I have seen pads that have the outer edge beyond the rotor a little bit, causing a lip to form at the outer edge of pad where it misses the rotor as it wears. If the od of the rotor is not running true, it could cause binding that feels like surge from warped rotors. It can also make the pads click & clack, but usually when brakes are not engaged.

Pete Haburt 76B
Pete Haburt

I'd agree with the slightly warped rotor as a first guess. But don't discount a loose wheel bearing, which can give the same symptoms.

Matt K.
Matt Kulka

Maybe stating the obvious, but check to confirm that the caliper mounting bolts are secure. It wouldn't be the first time I've seen them work loose.

Good luck.
Steve Mc

I had the caliper off last weekend to make sure the pads were seated properly and there were no problems of that nature. The bolts were quite tight..... The idea of a loose wheel bearing entrigues me. When I re-greased and installed the bearing last August everything went together firmly. I didn't know this was the sort of thing that could work loose. How does that happen?

Thanks,
Justin
Justin

As a rough check of the wheel bearing jack up that corner and rock the wheel. You should have just perceptible play in the bearings, but this will also reveal play in the axle bushes. Rule one when encountering a sudden problem: What did I last fiddle with? Did you miss a shim when reassembling? Did you recheck the end-float? Have you checked the run-out of the rotor yet?
Paul Hunt

This thread was discussed between 16/04/2002 and 17/04/2002

MG MGB Technical index

This thread is from the archive. The Live MG MGB Technical BBS is active now.