Old Britts
Commando Front Drum Upgrade Information
By: Fred Eaton

Summary:

This article will be assuming that you are rebuilding your front twin leading shoe drum brake completely. We will be having the following services professionally done; laced and true the wheel, Polish the hub and backing plate, the brake drum trued, and the brake shoes re-lined and arced to the drum. We will provide as much information about how to do the steps we are jobbing out and provide names of the firms that we use to perform the services we job out.

Four main performance enhancements:

These four enhancements will make your front twin leading shoe drum brake perform better than the stock Commando disc brake. If you just want to improve your front brake performance and do not want to do all four of the recommended enhancements, each enhancement will increase your performance. Just upgrading your brake shoes will improve your stopping performance. New brake shoes and upgrading your backing plate will greatly improve your stopping performance. The four enhancements are:

  • Turn the drum to guarantee roundness.
  • Have your front brake shoes re-lined or replaced with a modern friction material and arc to drum.
  • Bush the backing plate spindle shaft for proper fitment.
  • Install the brake performance kit (part # 06-3410).

Rebuilding steps:

When rebuilding a front wheel, you need to perform certain steps prior to another step, so the order you should follow is:

  • Remove the old tire and tube.
  • Unlace the wheel. If you are not going to reuse your old spokes, the easiest way to unlace the wheel is to use a bolt cutter and cut the spokes.
  • If you are going to reuse your rim, clean or re-chrome the rim.
  • Remove all the linkage on the backing plate.
  • Remove the four cam bushings and short pivot pin.
  • Thoroughly clean the backing plate.
  • Remove the bearings from the hub and thoroughly clean the hub and bearing spacer.
  • Install the spindle bushing upgrade (more on this later).
  • Have the backing plate and hub polished.
  • Lace and true the wheel. We use the experts at Buchanan's in California (626) 969-4655 to lace and true our wheels. What we do know about wheel lacing you can read in our article on Wheel Lacing Information.
  • Install the brake performance kit, see our article Drum Brake Performance Kit on how to install this kit.
  • Install the brake linkage on the backing plate.
  • Remove the old bearings from the newly laced wheel.
  • Send the wheel, backing plate and old shoes to Vintage Brake in California (209) 533-4346 to have the shoes re-lined, the hub turned and the shoes arced to the drum. Vintage Brake only rivets the new linings to the shoes and they need to be arced to the drum. According to the literature provided by Vintage Brake, if you want to arc the linings yourself, mount the shoes on the backing plate and turn on a lathe (300-350rpm) to .020" under the drum I.D. Turn down in cuts of .010".
  • Install new sealed bearings, see our article Wheel Bearing Upgrade Instructions for information on how to install sealed bearings.
  • Mount and balance the tire. If you are using spoke weights, we have some information about how we install the weights in our article Fastening Spoke Weights

NOTE:To true the wheel after having it laced, they like to have the bearings in the hub. To turn the brake drum, and it needs to be turned after the wheel is laced, they do not want the bearings installed. What we do is re-install the old bearings without the bearing spacer for wheel lacing, then remove the old bearings for turning the drum. This way you are not removing the new bearings, because you have to pound on the inner race of the bearing to remove them.

Spindle Bushing Upgrade:

The stock spindle bore in the backing plate is around .705" and the spindle is around .6673" or .002" under the 17mm (.6693") wheel bearing I.D. The .002" bearing to spindle clearance is what you want to achieve for the backing plate spindle bore. What I am told is that the factory increased the spindle clearance to allow for the brake shoes to self align themselves to the drum, but if the brake shoes are arced to the drum, this extra clearance is not required, and in fact lets the backing plate wobble in the drum, decreasing the efficiency of the brake.

What we do is take some .750" round 6061-T6 aluminum and bore it out to 17mm to make the spindle bushing. We then bore the backing plate spindle bore to around .748 and press the bushing into the backing plate. We then re-bore the bushing to 17mm.

Spindle Bushing

Backing plate with new spindle bushing.

Front drum brake services provided by Old Britts:

The prices are current as of 12/14/17.

  • (Part No. 06-3410/I, $454.99) Front Drum Brake Upgrade, Backing Plate Only. This service includes the spindle bushing upgrade and installation of the brake performance kit.
  • (Part No. 39-100209, $130.00) Front Drum Brake, Install Spindle Bushing Upgrade. This service is only the installation of the spindle bushing.


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