28 AA brake adjust advice

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birdacre
Posts: 284
Joined: October 8th, 2013, 2:37 pm
Body Type: AA express
Model Year: 1928

28 AA brake adjust advice

Post by birdacre » July 17th, 2017, 7:38 am

i have a 31 model A and made up a piece of wood with the notches to engage the brakes at different points for adjustment. works great and is illustrated in the model a repair manual. Is this method good for AA brakes as well. i tried it and am experiencing difficulty with rear brakes. does not seem to have enough travel in pedal to lock or unlock rear drums, seems to be caught in the middle when wood block is removed. drums still hang up with no pedal. if backed off a few notches they then fail to lock up under full pedal. all new shoes, springs etc. anyone have any ideas, does this indicate MORE travel needed as in lengthen rods to rear. or is it LESS length for quicker response. would love to hear any advice. thank you, kevin

Stakebed
Posts: 1035
Joined: June 14th, 2007, 7:29 pm
Body Type: Grainbox
Model Year: 1929
Location: Illinois

Re: 28 AA brake adjust advice

Post by Stakebed » July 17th, 2017, 8:40 am

hmm let me see if i understand:


tightening the wedge on the backing plate will lock them tight

pedal does not lock them tight when the wedge is adjusted to barely any drag

Questions:

were the shoes arched to the drum?

were the backing plates built up and ground flat?

was the wedge replaced or checked for wear? Same with cam and all brake parts?

Are the wedges on each shoe that the adjusting cone rub on measure the same length? Does the cone have nice easily identifiable clicks?

If using used parts you may have to adjust the wear out at the rods so shorten them.

First off ignore the wood block

remove the brake rods

adjust the wedge on the back of the backing plate to full tightness then back it off in one click increments till you can rotate the wheel with barely audible drag felt/heard.

spin the wheel and pull on the brake arm and note how far and at what angle it has to move to engage the brakes to lock up. It shouldn't have to move very far. Ideally like the front brakes you want full lockup when the arm is 90* to the road for max leverage so relaxed the rear should be tilted 15* backwards with all slop removed. If your going past 90* for lockup your leverage is lost and wont get a good brake pedal.

if that all checks out then pull the slack out of the brake arm and adjust the rods accordingly - might be different on each side due to wear so ignore that block o wood.

njcar757
Posts: 67
Joined: March 4th, 2009, 4:00 pm
Body Type: closed cab
Model Year: 1929

Re: 28 AA brake adjust advice

Post by njcar757 » July 17th, 2017, 9:04 am

Recently I completely dismantled a 29 AA differential, starting with the hubs and all the brake parts. When I got to the 2 cams, they were completely froze solid inside the camshaft along with the 2 spring behind them. The cams are supposed to float inside the camshaft and find the drum.
hope this might help nick c

birdacre
Posts: 284
Joined: October 8th, 2013, 2:37 pm
Body Type: AA express
Model Year: 1928

Re: 28 AA brake adjust advice

Post by birdacre » July 17th, 2017, 9:20 am

thank you for your help. i appreciate your time and advice. i will keep you posted. kevin

Stakebed
Posts: 1035
Joined: June 14th, 2007, 7:29 pm
Body Type: Grainbox
Model Year: 1929
Location: Illinois

Re: 28 AA brake adjust advice

Post by Stakebed » July 17th, 2017, 10:37 am

njcar757 wrote:
July 17th, 2017, 9:04 am
Recently I completely dismantled a 29 AA differential, starting with the hubs and all the brake parts. When I got to the 2 cams, they were completely froze solid inside the camshaft along with the 2 spring behind them. The cams are supposed to float inside the camshaft and find the drum.
hope this might help nick c
yea that too, remove any groove found in the cams so it can easily float and not catch.

njcar757
Posts: 67
Joined: March 4th, 2009, 4:00 pm
Body Type: closed cab
Model Year: 1929

Re: 28 AA brake adjust advice

Post by njcar757 » July 18th, 2017, 6:59 am

By any chance are the cams in an automobile and a AA truck the same?
nick c

Stakebed
Posts: 1035
Joined: June 14th, 2007, 7:29 pm
Body Type: Grainbox
Model Year: 1929
Location: Illinois

Re: 28 AA brake adjust advice

Post by Stakebed » July 18th, 2017, 7:23 am

I dont think so.

Bob C
Posts: 1058
Joined: April 24th, 2003, 11:50 am
Body Type: Mail truck, Stake tr
Model Year: 1931
Location: SO CAL

Re: 28 AA brake adjust advice

Post by Bob C » July 18th, 2017, 7:47 am

The parts book shows the cam the same as the Model A , A-2230 rear brake cam.

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