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'66 BJ8 brake drum spec?

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TRdarrel4

TRdarrel4

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I need help.

Does anyone have a factory spec for the maximum grind on a BJ8 brake drum? (and exactly how is this measured, anyway? I'm guessing: inside diameter?)

You see, I am in the midst of a mild restoration of a '66 BJ8 "barn-find" that had been on blocks for the past 25 years (with some rain exposure). Of my challenges is the resurfacing of the rear drums. I have the suspicion that they were nearly new at the time the car was put up. And considering this, I am certain that there is enough 'meat' there to mill down the accumulation of rust that I have. My problem is that my shop will not do the job without having that factory minimum / maximum measurement. Any help would be appreciated.
:thankyousign:
Darrel
'64 TR4
'66 BJ8

. ..^(^..aloha..^)^.. .
 
this has been discussed before on the forum with no results:

https://www.britishcarforum.com/bcforum/u...ency#Post860200


Re: rotor thickness discrepency [Re: Hoghead]
Bob_Spidell
Jedi Knight

Registered: 02/25/07
Posts: 947
Loc: California USA
FWIW, I tried to get my BJ8's rear drums turned a few years ago; the techs couldn't find a minimum thickness spec anywhere and refused to turn them. In CA, it's apparently a pretty serious offense (criminal, even) to turn rotors or drums down below spec. Sounds like there aren't any specs for rotors, either.

I bought Moss rotors a few years ago on sale. They are Brembo; good enough for me. You could call Moss and see if they are still selling Brembos.

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Thanks Tim K. for your response.

I was afraid that might be the answer. Looks like there simply was never a spec issued. That sure complicates things.

note: I did, however, find a reference to a .335" (8.51mm) minimum for rotors, in an original BMC workshop manual.

___________________________

Darrel
'64 TR4
'66 BJ8

. ..^(^..aloha..^)^.. .
 
8.51mm for a front rotor seems very thin if they start life at 12.5mm
In any case new ones are cheap, and cheaper last week at 30% off, at Moss and hardly worth the bother of turning
 
TRdarrel4 said:
I need help.

Does anyone have a factory spec for the maximum grind on a BJ8 brake drum? (and exactly how is this measured, anyway? I'm guessing: inside diameter?)

You see, I am in the midst of a mild restoration of a '66 BJ8 "barn-find" that had been on blocks for the past 25 years (with some rain exposure). Of my challenges is the resurfacing of the rear drums. I have the suspicion that they were nearly new at the time the car was put up. And considering this, I am certain that there is enough 'meat' there to mill down the accumulation of rust that I have. My problem is that my shop will not do the job without having that factory minimum / maximum measurement. Any help would be appreciated.
:thankyousign:
Darrel
'64 TR4
'66 BJ8

. ..^(^..aloha..^)^.. .
Click to expand...

Darrel, call Allen Hendrix at Hendrix Wire Wheel (https://www.hendrixwirewheel.com). Allen balances brake drums and may know if there is a limit thickness stamped anywhere on the drum, or he may know of the limit otherwise.
 
Hi there Hoghead.

Re: that rotor spec ..
Personally, I'd agree that to mill nearly a third of the material from the original disc seems questionable. I'm just relaying the info I'd pulled from the factory manual. Not saying I'd risk, or advise, such an aggressive cut - especially considering that you can pick up an aftermarket replacement for not much more than the shop cost to do so.

Thanks for your input. :iagree:

( btw - I was able to have my rusty rotors machined to a factory finish - and I still have 10.42mm on the bone :thumbsup: )
 
I dug out the Brembo BJ8 disks I bought from Moss a few years ago (bought them on sale but haven't installed them). They have "MIN TH. 11,4 MM" on the edge (11,4 is European for 11.4). IIRC, BJ8 disks are half-inch wide (12MM and change), but disks for earlier Big Healeys were thinner (3/8"?).
 
I too saw the 8.51 in the manual but do not believe it and it may be a carry over from the earlier thinner rotors. I would think that 1mm would be max

My Tiger uses the same Girling 16P callipers and will check the manual and advise
 
Bob is correct, the early discs were .375 thick and the spec that Darrel quotes at .335 is correct for early discs.= max turn is .040 off the original.

BJ8 rotors are .500 thick and I have a set that have the same stamping on the edge that Bob said, min is 11.4MM.
 
TRdarrel4 said:
...I have the suspicion that they were nearly new at the time the car was put up. And considering this, I am certain that there is enough 'meat' there to mill down the accumulation of rust that I have. My problem is that my shop will not do the job without having that factory minimum / maximum measurement. Any help would be appreciated.
Click to expand...


What I would do: get some emery cloth and sand the rust off the inside of the drums (use some chemical rust remover if you like). Clean thoroughly. Install new shoes if necessary and break them in properly. Drive and enjoy your car.
 
Thanks guys for that info. Once again, things seem to make sense -- at least with regard to the rotors. Not so much with these drums, however. :frown: Neither Moss tech support nor the guys at Hendrix could recall such a spec for these.

In the end: new drums and rotors it is! And that solves that.

Much Mahalo for all of your combined knowledge and wisdom.
 
I know this is an old thread, but I bought some drums from Moos and the max. inside diameter was stamped on the edge as 281 MM. I also called Moss and got the same number. Unfortunately the drums I received were not quite round and caused a shudder or vibration when braking, so I sent them back. They were only slightly under the 281 max. diameter, so didn't have enough "meat" on them to be turned to true.
 
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