Adjusting Front Brakes on 1929 Model 633

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29wrench
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Joined: Tue Jan 12, 2021 2:51 pm

Adjusting Front Brakes on 1929 Model 633

Post by 29wrench » Tue Jan 12, 2021 3:07 pm

I had the brake shoes relined on my Model 633 and have followed the Bendix Brake Service Bulletin #204 (12/1/29) in adjusting them. I followed the procedure with the wheels straight. With the front right and left balanced and no brake application, I turned the wheel hard left and the left wheel locked up while the right was free of any drag. Reversing this, turning hard right, the right wheel locks up and the left is free of any drag. This can't be right. Any suggestions?

Adam
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Joined: Fri Sep 04, 2009 4:15 am
Location: lincolnshire, uk

Re: Adjusting Front Brakes on 1929 Model 633

Post by Adam » Mon Jan 18, 2021 2:03 am

That is strange and can only mean that at the extreme of steering lock, the brake cross-shaft is pulling the shoes into contact with the drum. Difficult to say without seeing it, but it might be worth checking that the swivel joint where the cross shaft enters the back plate is nice and free, that the steering lock is not adjusted to be too tight (check the lock stops) and that the shoes are not adjusted so tight as to cause them to drag as a quirk of the linkage. I hope you find the solution, but please let us know because I will be working on my 1928 533 brakes soon.

Adam..
"Do not underestimate the English cousin.....they are not as stupid as they look!" - Signor Altabani in The Italian Job.

29wrench
Posts: 3
Joined: Tue Jan 12, 2021 2:51 pm

Re: Adjusting Front Brakes on 1929 Model 633

Post by 29wrench » Sun Jan 24, 2021 8:35 am

Thanks Adam for these suggestions. I didn't adjust the steering lock stops from their previous settings and I never experienced any braking problems before (admittedly I never tried this extreme steering position brake test with everything off the ground). The linkage mechanism was free for both right and left sides. I'll have to dust off the geometry books to see if the basic layout of the design results in cam actuation with the turning of the wheels (again, hard to imagine the design working satisfactorily if this were the case). The brake linings are all new but since I can adjust them to spin freely at any steering angle without drag (brake cables disconnected) I don't see them as the problem although they are the only physical components in the system to be changed.

If I adjust the cable adjustment nuts for no brake drag in the extreme steering angles, the cable hangs slack and loose in the other positions and is not effective in actuating the brakes - no surprise. So, I'm back to making the basic adjustments with the wheels steered straight as the instructions seem to imply. I'm using the Bendix Brake Service Bulletin #204 dated Dec. 1, 1929. Nowhere do they ever suggest making settings or even checking the brakes in anything but the straight position.

Adam
Posts: 1107
Joined: Fri Sep 04, 2009 4:15 am
Location: lincolnshire, uk

Re: Adjusting Front Brakes on 1929 Model 633

Post by Adam » Wed Feb 03, 2021 5:54 am

You certainly seem to be on top of this. Might it be so simple as to require adjusting the shoes a little bit slacker, then bedding the linings in a bit before final readjustment? I cannot offer any reasons why that should be, but I would try it and see if the problem goes away.
"Do not underestimate the English cousin.....they are not as stupid as they look!" - Signor Altabani in The Italian Job.

29wrench
Posts: 3
Joined: Tue Jan 12, 2021 2:51 pm

Re: Adjusting Front Brakes on 1929 Model 633

Post by 29wrench » Sun Feb 07, 2021 1:01 pm

I'm with you on this one Adam. I ran through the adjustment and balancing procedure one more time and buttoned it up. As soon as the weather warms up a bit, I'll try it on the back roads here and see if it beds in. The brake cables to the front wheels are already looser (almost slack) than I recall but the wheels do lock up when the brake pedal is fully depressed. I'm going to give it a go.

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