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Hello Everyone.

I'm working out the bugs in my 31 AA, which I acquired in April and whose engine I rebuilt over the summer. Working on the brakes, I found them getting bound up by this guide on both sides of the frame. It is directly below the center of each door. When I press the brakes several times, these guides will either rock back or forward and, depending upon the direction they lock, the brakes either remain partly engaged or won't fully engage.

In the photos below, the guide is centered but is freely pivoting. In the yellow circle, you can see how it's bent the rod when the brake pedal is crushed to the floor, trying to fully engage the brakes but is prevented from fully engaging by this 'sprung' guide.

My question is: Are these guides supposed to be fix (bolted tight) or should they be allowed to pivot?

Thank you!!

That is not a guide, there is two brake rods that hook together there and that bracket should pivot.

Bob

Hello (again) Bob,

That's not what's happening with my truck - it's one long rod from the forward bell crank to the rear brake. And that 'guide' pivots and locks up, pointing forward or back, binding up the rod's movement.

I can see that it does make mechanical sense to have two shorter rods instead of a single, long rod which is more subject to bending, kinking or other undesired movement/vibration.

Does anyone happen to have a diagram or photo of how the two rods are supposed to couple at that pivot point? I will have to fabricate it from my single rod.

The first two images show the brake rod hookup on a AA-157 chassis. Note the retracting spring is missing.

 

 

This is on a 1929 AA-131:

 

The June, 1930 Service Bulletin shows the method of attaching
the retracting spring:

 

The best I can tell from the parts books is the rod from the front brake actuator to the rocker is 61 5/8"
without the adjustment eye and the rod from the rocker to the brake cross shaft is 25 7/16".
This is for the front brakes on a 30-31 long wheel base.

Bob

Phil, thank you very much for the information!

Correction - this rod is to the front brake, not the rear.

So, it appears that I am missing the springs on either side as well as having a full length rod passing through that 'guide' and NOT anchoring at it. I will have a look at the vendor catalogs and see about the spring. I should be able to break the rod and weld on eyes.

The 30-31 did not use the springs. The springs you see are for the rear brakes on the 28-29.

Bob

Only the AA157 used a front brake rocker arms with two rods. The cross shaft to front rocker arm rods were 25-7/8" long with an eye on both ends. The front rocker arm to front axle was 61-5/16" long with an adjustable clevis at the front and an eye at the rear. This was the same as used for the 1930/1931 AA131's. The rod had a spring pocket button which was 27-3/8" from the fixed eye. The button was for the brake retracting spring. The spring was the same as used for the A chassis. It was bolted to a bracket riveted to the frame.

Thanks Neil.
Mine is a 157 wheelbase. Looking over the vendors, I don't see a two-rod kit. So, I'll either cut them and weld eyes or thread clevises.

rustywiring wrote:Thanks Neil.
Mine is a 157 wheelbase. Looking over the vendors, I don't see a two-rod kit. So, I'll either cut them and weld eyes or thread clevises.

I don't believe vendors sell any brake rods which are AA parts. The 1928 and 1929 AA's used the A chassis front brake rods, brake equalizer to operating shaft rod, hand brake rod to equalizer rod, and (for trucks with emergency brakes) the break pedal to cross shaft rod.

You are correct Neil - vendors only sell fronts for 28/29. Took me awhile but i was able to scare up a set of rears for mine. If you need one or two rods I may have an OK condition one or at least one i can get measurements from so you can make one. Not too bad of a job to do if you must make them.

Revision 4 of the Restoration Guidelines & Judging Standards (available from MAFCA or MARC). It has a new E Supplement (Heavy Commercial Vehicles). This supplement includes area E7 - Brake System which has an AA Brake Rods Table. This table is subdivided into the four AA Brake System designs. For each design each brake rod is listed showing the diameter, length, front/rear eye or clevis, and the spring pocket button location. The AA brake system are:

• • Design 1 – Trucks without emergency brakes (through 1928)
  • Design 2 – Trucks with emergency brakes (through 1929)
  • Design 3 – AA131 trucks (1930 through end of production)
  • Design 4 – AA157 trucks (all production)

Fantastic information, Neil. Thank you again.

speaking of brake rods, the beads on my front brake rods were about 6" forward of the return springs (in addition to being heavily pitted, worn and bent) so I replaced them with rods offered by Snyder's and the beads are still shy of the springs.
Has anyone else encountered this? Snyder's only offers one front rod for 1930-31. Is there a source for different rods or have I got something wrong?

are you absolutely sure you ordered/clicked on A-2501-A and not the number for the rear brake rods that are 4" longer? looks like its about 4" off in your pic....

I used to have some oddball rods that the bead was not where it was supposed to be (old repops) but you said you got new and snyders is a reputable place...

i would measure what you got...