Front Brake Shudder

[Tony]

Having fitted new 8 inch brakes to my Series 2 car I find that I am getting a brake shudder very similar to what you get when a drum not true. The car is fitted with brand new drums, shoes and brake cylinders (master & slave).

I was convinced the new drums were not round so I took them to a local engineering firm who check them and confirmed that they were good. However he pointed out that for position, the hub fits against the rebate on the drum and advised me to check the clearance. I did this and found that I could get a 10 thou feeler gauge between the rebate and the hub, meaning that there was a 5 thou clearance all round. (see photo). I checked the hub against an old drum on a friend’s car and found that the hub fitted snugly against the rebate with no measurable gap.

I contacted the supplier of the drums who advised that they had had a batch where the holes for the 2 locating screws were misaligned and the solution is to remove the screws and then the drum should centre itself.

I have discussed this approach with an ex DfT engineer who advised me that mating surfaces should mate and it could be potentially dangerous for the drum to ‘float’ as advised.

My inclination is to chuck the new drums and get some good secondhand ones. But first I wondered if anyone else had met this problem. Any ideas or advice would be appreciated.
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[bmcecosse]

The screws effectively do nothing (the drum is clamped in place by the wheel/wheel nuts - so try with them out. And I never considered that the drum would face up to the 4 corners of the hub.....seriously - it may just be the new surface of the drum needing to be 'run in' against the shoes - and did you file the leading edge off each brake shoe? Your's is not the first case of 'shudder ' with the new parts - But I would persevere, work them hard and see if they settle down. Could also try swapping the drums side to side - it may help.

[mike.perry]

I have my doubts about the locating screws, you should fit the drum and tighten it on to the hub using the wheel nuts, then fit the screws which are retaining screws, simply there to keep the drum against the hub, not to tighten the drum which is the cause of the crosshead slots getting bxxxxxd. If the screw holes do not line up with the threads in the hubs then the supplier should turn the drums through 90deg and re drill the holes at his own expence, not fob you off with dodgy drums only after you have complained