m38a1 brake drums

circleburner12 · Post by **circleburner12** » Wed Jan 11, 2012 6:54 pm

took them to the machine shop to be turn, and was told they could'nt be turn because the way they were made.

can anyone explain this to me. thanks

danrothe2001 · Post by **danrothe2001** » Wed Jan 11, 2012 11:49 pm

I just did mine and they were awkward. It has to do with the large hole in the center along with the small diameter of the drum. I used a small cup on the inside to clear the cutter bit. Then I put the cone and spring on the outside which is backwards to the norm. Then I used a larger cup on the outside to clear the large cone. Everything worked fine. Just have to think outside the box instead of blindly following instructions.

Dan

artificer · Post by **artificer** » Thu Jan 12, 2012 12:53 am

You are aware that you need to fit oversize linings to the shoes otherwise you will not get good brakes.

Recommend oversize linings bonded then cam ground to suit the new drum diameter.

Needs to be done at a reasonably good brake shop not the chain variety that you are possibly going to now.

Also be aware that drums should be machined in pairs or all 4 to be the same diameter.

Off course the drums can be machined unless too much material needs to be removed.

Post by **wesk** » Thu Jan 12, 2012 1:23 am

As mentioned above the shop you use should be a very well equipped (both personnel and machinery).

Unless you are building an interstate rocket jeep then the light weight 50 MPH unit can do without cam grinding linings.

You should always increase the installed diameter of the shoes the same amount that you cut out of the interior of the drums. There are oversize shoes available and there is the art of shimming riveted shoes.

Also keep in mind that federal and state laws usually prevent a shop from turning drums past their legal wear limit.

artificer · Post by **artificer** » Thu Jan 12, 2012 2:16 am

With all due respect Wes let me add to the "brake knowledge pool" here:
Cam grinding shoes as suggested does nothing more than ensure the linings are precisely concentric with the newly machined drums when the re-lined [cam ground] shoes & linings are first adjusted....what that has to do with interstate rocket ships or Jeeps is in someone's imagination. Maybe it's a terminolgy thing that brake blokes have been exposed to.

Post by **wesk** » Thu Jan 12, 2012 1:58 pm

With all due respect John, the need for cam grinding jeep 8" and 9" brakes on stock jeeps is really not necessary.

Interstate rocket is my easiest identifiable description of a jeep that is modified to run at the much higher interstate speeds in the US. Very much a reality and not imagination.

Lets leave our distracting discourse for the PM system if you feel the need. Here we should post the two opinions and leave it at that and move on unless we have some new case supporting industry data to introduce.

TomM · Post by **TomM** » Thu Jan 12, 2012 7:04 pm

find a different shop. I just had two turned last weekend.
Tom

artificer · Post by **artificer** » Thu Jan 12, 2012 7:48 pm

Far from being a distracting discourse there are right ways to do things & whether the drums are 9" or not is absolutely irrelevant.
Also a number of "enlightening points" were made for the non tradesmen such as ensuring all drums are of equal diameter etc

A simple google search on "how to cam grind brake shoes" resulted in

Collector Car Restoration Bible: Practical Techniques for ... - Google Books Result

books.google.com.au/books?isbn=0873499255...Matt Joseph - 2005 - Antiques & Collectibles - 400 pages
Then, shoes were "arc ground" ("arced") or cam ground to specification. On non-servo brakes, this grind was from 0.010 inch to as much as 0.025 inch under.....including a paragraph starting with....YET RECONDITIONING WITHOUT THE BENEFIT OF AN ARC/CAM GRIND IS POOR PRACTICE

anyone interested can read the full page & I will rest my case after asking one other question "why when some folk reline brakes do they pull in all different directions even when all indications are they are adjusted perfectly?"

I agree with Tom....go to a real brake shop & it really helps if we know where you are e.g. if you were in KCMO I would suggest Gooch Brake & Clutch.

circleburner12 · Post by **circleburner12** » Thu Jan 12, 2012 8:53 pm

i dont have a shop that relines brakes shoes anywhere close to me, so that's out of the question.

wesk, is the oversize shoes necessary? if so where can they be purchase (orielly's autozone)?

tom, where did you get your drums turn?

thanks

artificer · Post by **artificer** » Thu Jan 12, 2012 11:22 pm

If you have machined or re-ground the brake drums & you want efficient brakes you must use oversize linings equal to the material removed from the drums.

If you don't depending on how much material is removed from the drum only a small centre section of the linings will be in contact with the drum when the brakes are applied.

Post by **wesk** » Fri Jan 13, 2012 12:19 am

Hello Circleburner,

As I already posted above:

You should always increase the installed diameter of the shoes the same amount that you cut out of the interior of the drums. There are oversize shoes available and there is the art of shimming riveted shoes.

This you can do yourself. You just place the appropriate shim stock (equal to the cut made on the drums) and add it between the shoe and the lining.

Why don't you call a local heavy truck fleet operator and ask him where he gets his brake relining done?

TomM · Post by **TomM** » Fri Jan 13, 2012 8:24 am

Circleburner,
I usually keep my business local. There is an old skool auto parts store in Wakefield Rhode Island - County Line Auto. They do not have internet, mail order, facebook or ebay stoes. Just a phone and parts books. Small shop, wood floor, shelves groaning from parts loads, little room to walk and a counter guy who knows what a flathead is and what drum brakes are. He maintains the small machine shop in the back. Drums turn for $12 each.
I farm it out shoe relining. My original Bendix shoes went to Then & Now
. They bond instead of rivet They also exchange so if you want your exact cores back you need to talk to them. I dont know how they would handle different size requests.
THEN AND NOW AUTOMOTIVE
447 Washington St Weymouth Ma 02188
oldpartstom@aol.com
www.then-now.com OR email: our1932@aol.com

Try to find those local shops that know what you are talking about. Chain stores dont want to work with you if your car is pre-2005.

Suggestion: update your profile with a location so that others in your area can give you their local information and resources.

Tom