The Stovebolt Site Forums The Parking Lot Panels 'N Burbs 1950 Suburban Brake Drum Tolerences?

Hi Guys, you helped me out big time with my last post so I thought I'd lean on ya again. I need to get my brake drums turned but my local machine shop doesn't know what the tolerences should be...and obviously either do I! Anyone that can aim me in the right direction would be awesome!

If he has a brake drum mic.(micrometer) that will tell him.
Example: if its a 10 inch drum,and its turned past a certain measurement,then its not usable.

The brake drum mic's. ive seen,have a red zone to tell you the drums too far gone.

Thanks Marty, maybe he just didn't want to turn them? I'll try a different shop.

As a rule-of-thumb, the limit for turning brake drums is .060" oversize, but some can go larger. Newer drums are often marked with the maximum size; yours might be marked if they have been replaced. The size will be stamped/cast into the open rim of the drum if it is there. Otherwise, you need to know the stock diameter before you can determine if your drums can be turned, and how much they can go. It is not necessary to remove all trace of blemishes from the drum in order for it to be satisfactoy for use- you can turn a drum up to the limit and leave small imperfections/grooves if they don't go completely around the shoe surface. Different shops have different views of what is allowable, and they even make mistakes with their drum gauges. Getting another opinion is a good idea.

Harvester

So that's the million dollar question.......what is the stock diameter for a Suburban 1/2 ton brake drum? it was built November, 1950, so a lot of the parts on this are actually for a 1951 Suburban, I know the brake shoes and wheel cyl are 51's.
Thanks for the help Harvester.

I'll see if I can find the original drum size. Might take a while.

Harvester

Unless you get those odd size mid 1980's GM truck shoe sizes. What was up with that??

From my 48-51 Chev truck shop manual: Half-ton truck has 11 inch drums, front and rear; 3/4 ton has 12 inch rear drums, 11 inch front. Maximum size is .060" over for both. Your '50 model has 'Articulating Link' brakes with the anchor pin at the bottom; they look different from the 'Duo Servo' setup that is the later model system and has the adjuster at the bottom. The Duo Servo system was used in 1951 and later vehicles. I don't think your truck uses primary and secondary shoes- I'll have to look at the shop manual again. If you are honing the cylinders, the maximum size is +.004" for wheel cylinders; +.005" for the master cylinder, measured with a thin feeler gauge between the piston and cylinder bore- I don't think you can find brake cylinder gauges any more.

Harvester

Thanks Harvester for all your time and research

If your truck is a 1/2 Ton, you are lucky because you can buy the drums new. I believe Jim Carter lists new drums for the 1/2 Ton of that year.