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MG MGB Technical - Brake Rotor Problem?

I just purchased a '68 B roadster. It came with new brake rotors and pacs in boxes. The first time I drove it above 40 MPH I found that when the brakes are applied above 40 MPH there is a violent vibration and it's felt through the steering wheel. When the brakes are applied below 40 MPH they are smooth. I intended to install the new rotors and pads but would like to ask if there are any other likely sources of the problem (like front suspension bushings, etc. maybe?)
J.C. Weidner

Bad front wheel bearings?
Steve S.

JC. As Steve notes, bad wheel bearings can have some effect on how the wheels react to braking. Shifting crossmember can have some effect. Worn tie rod ends. Warped rotors. Wheel bearing end float not set up correctly. Bad wheels, especially wire ones. Wheels not tight on axles. Kingpin/stub axle problems. Steering rack not tight to crossmember. U joint in the steering rack to steering column going bad (actually happened to me--checked all of the above, all was good, U joint tested bad).

Best thing to do is to make a through inspection of the front end and check the entire system out. If you find a problem, it will give you a chance to correct it while you are replacing the rotors and pads (which requires removing the hubs, making a good time to check the bearings, grease seals and set up of those systems).

Les Bengtson

Did you feel any vibration or pulsing in the brake pedal?


I feel very slight movement below 40 MPH (probably slightly warped disc). That's why I questioned the need for new discs. However, since the PO purchased the discs and they came with the car, I intend to replace them. I just wondered what other faults could cause the problem. Les has provided sufficient ideas to keep me occupied for some time. Thanks to all.

J.C. Weidner

This thread was discussed on 25/02/2007

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