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MG TD TF 1500 - Pulsating Front Brake

At times my 52 TD would uncomfortably pull to the right. Otherwise the brakes worked fine. After checking the archives for solutions I discovered my right drum was visually out of round compared to the left drum. I figured the brake pads would catch on a low section of the drum and cause the sudden pulling to the right. I brought a very decent replacement drum (used) which was visually more round when spinning on the axle hub. No drum measurements were made however. After pulling a sticky inner wheel bearing and replacing the oil seal I put the drum assembly back on the car and torqued it close to 70 ft. lbs. Well the pulling to the right is gone but now the front right wheel has a very noticeable pulsating and choppy vibration when stopping. Stopping on a gravel road shows roughly equal stopping tracks for both front wheels. I was wondering, I did not file the brake shoes which were good but obviously worn in to the old "out of round" drum to match the replacement "round" drum. Only read about this after I refitted the brake drum. Can this make such a difference and be the primary cause of my choppy front brake? The archives don't have much on the cause of a choppy brake drum, at least what I can find.

Any ideas on what I should try next would be appreciated. Thanks, Tim


Tim Debes

The pulsing brake pedal is generally caused by out of round brake drums (or warped rotors on disc brakes). As the drum rotates and the surface moves in and out in relation to the brakes shoes it will cause a higher and then lower pressure in the brake line which you will feel in your braking foot. It's almost always caused by overheating the brakes. If it isn't excessive it can be corrected by having the drum turned.
MG LaVerne

Thanks LaVerne, I have a local shop who can do this (family friends) and will report back. I will have them turn both drums and go with the best one. Your advice makes sense to me. Tim
Tim Debes

Beware Tim that if the drum has been turned in the past or if it requires a great deal of material to true up the drum, it may become unuseable. I don't believe I have ever seen a number for the maximum useable ID or the minimum wall thickness but I would imagine somebody here should have a useable working number. Also you may find that the brake adjusters will not travel far enough to allow a proper adjustment of the shoes after having them turned. If the drum is useable and that happens, you can shim the adjusters to make them serviceable.

Have the shop do a good inspection for cracks before investing the time to turn the drum.
MG LaVerne

Ok, I will check the archives and my manuals for a max ID. No use in making the drums unusable or unsafe. The original drum took four click turns to properly set the brake shoes. The replacement drum took only 2 click turns so I may have enough drum thickness to turn the drum into a true round drum. Thanks for the seasoned insight. Tim
Tim Debes

9" TD drums are very robust, and very seldom need turning at all. Obviously, an out-of-round situation needs addressing.

I use 9.10" as my standard for when a drum is questionable, although I have seen them much larger on cars that performed just fine. You will run out of adjustment, and will need to shim the adjusters with a clipped penny or a welded plate on the bottom of the mask.

Tom Lange
MGT Repair
t lange

This thread was discussed on 18/10/2015

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