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Question on rear brake drums BN6 wire wheel

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BN6_2197

BN6_2197

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Gents,

I have some questions about original brake drums for BN6 with wire wheels:
* what is the original part number (mine have 1B.7526 / MOWOG)?
* what is the original color (mine are silver painted)?
* are they ribbed or not ribbed (mine are ribbed, some suppiers say ribbed version is for disc wheels)?
* what is the maximum inner radius (my radius is irregular and i wnt to bore them to get the radius regular)?

By the way: what is the best procedure to remove the brake shoes?

Volker
 
for removing, i usually just grab one of the shoes and slide up off the adjuster. of course it helps to have it backed off all the way first. once you pop one out they come right off. if you are not changing the wheel cylinders i usually put a wire tie around it so the cylinder can not expand.

take some pictures as to the orientation of the shoes and how the springs are hooked before you start. good to have a reference if your memeory is as short as mine.
 
It was always my understanding that the originals were ribbed (at least for wire wheels) but the suppliers have cheapened up and only offer the smooth as replacements...Look at the link Steve posted from Moss, the drawing clearly shows ribbed for wire wheels but if you click on the drum in the parts listings below, the picture is of a smooth drum for wire wheels. I do believe the ribbed ones cool better.

Moss doesn't list a drum for the disc wheels and I'm not sure that they are available anywhere else. I have bolt on wheels and before I changed to discs I used wire wheel drums and an aluminum spacer to get the correct wheel mounting surface - a lot less unsprung weight (and you can find the ribbed ones sometimes on ebay)
Dave
 
Gents,

can somebody comment on the original color and the max radius for booring?

Volker
 
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I tried to get a local shop/store to turn the drums on my BJ8. They could not find a max. diameter/min. thickness--whatever they use--for the drums and refused to turn them; said here in California it is a crime (felony?) to do so without a spec. I believe the original/correct color is a satiny silver similar to the color used on painted wheels, but I painted my BJ8's drums black because it really makes the chrome wires stand out.
 
My 62 mkll side shift tri-carb (built Nov. 61) has wire wheels with silver painted ribbed rear drums.
 
Bob_Spidell said:
I tried to get a local shop/store to turn the drums on my BJ8. They could not find a max. diameter/min. thickness--whatever they use--for the drums
Click to expand...

My local garage is willing to tunr them but they asked for a max diameter since the radius of the brake shoes must fit after processing the drums.
 
My local garage is willing to tunr them but they asked for a max diameter since the radius of the brake shoes must fit after processing the drums.​
Click to expand...
​
The max dia. call-out is to make sure the drums are still safe and not overly weakened by removing material, and has nothing to do with the shoe arc.
Your shop should also be able to re-arc the shoes - that is normally what is done, drums turned and then shoes re-arched to match.
Dave
​
 
Bob_Spidell said:
I tried to get a local shop/store to turn the drums on my BJ8. They could not find a max. diameter/min. thickness--whatever they use--for the drums and refused to turn them; said here in California it is a crime (felony?) to do so without a spec. I believe the original/correct color is a satiny silver similar to the color used on painted wheels, but I painted my BJ8's drums black because it really makes the chrome wires stand out.
Click to expand...
Bob what they told you was incorrect. They probably never had anyone that was a licensed inspector in their employ
A direct quote from the May 2015 version of the California Brake Adjuster Handbook regarding certification of a brake system states:

"Before you reline any brakes, measure the drum diameter with a micrometer. It is recommended that you do not machine a drum to exceed the maximum diameter as identified on the drum. It is also recommended that an older drum not identified with a maximum drum diameter should not be machined to exceed 0.060 inches inside diameter over its original size. If the vehicle or brake parts manufacturer provides a specification,such specification may be used. This recommendation applies to light-duty passenger vehicles, including light trucks."

Having once possessed a California Brake Inspection License, this has been the standard for many decades. Personally, I would feel more comfortable sticking to under .030" above the original diameter.
 
red57 said:

​
The max dia. call-out is to make sure the drums are still safe and not overly weakened by removing material, and has nothing to do with the shoe arc.
Your shop should also be able to re-arc the shoes - that is normally what is done, drums turned and then shoes re-arched to match.
Dave
​
Click to expand...

You are not likely to find any shop today that has the equipment to re-arc linings. The last time I had access to such equipment was nearly 30 years ago AND we were not allowed to use it due to lack of dust collection equipment necessary to prevent any asbestos dust from becoming airborne. While today's linings should not use any asbestos, who really knows if that is the case when the linings likely come from China.

Most reputable brake shoe suppliers manufacture their linings to be arced for a drum that is .030" oversize. I would not assume that the suppliers of brake linings for our vehicles follow that standard. It just means that there will be a longer "break-in" period for the drum brakes as they will have to wear in to match the drum diameter.
 
CraigC said:
Bob what they told you was incorrect. They probably never had anyone that was a licensed inspector in their employ
A direct quote from the May 2015 version of the California Brake Adjuster Handbook regarding certification of a brake system states:

"Before you reline any brakes, measure the drum diameter with a micrometer. It is recommended that you do not machine a drum to exceed the maximum diameter as identified on the drum. It is also recommended that an older drum not identified with a maximum drum diameter should not be machined to exceed 0.060 inches inside diameter over its original size. If the vehicle or brake parts manufacturer provides a specification,such specification may be used. This recommendation applies to light-duty passenger vehicles, including light trucks."

Having once possessed a California Brake Inspection License, this has been the standard for many decades. Personally, I would feel more comfortable sticking to under .030" above the original diameter.
Click to expand...

Thanks for the info, Craig. I'll print out a copy of the relevant passage and show to the shop, and if they won't do it I'll find a shop who will (maybe the shop couldn't find the original diameter spec, and gave me a line of manure).

ps. The handbook looks to be good bedtime reading.
 
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