Has anyone experience or give me tips or trick’s in tuning and adjusting the mechanical brakes (and hand brake) for my car?
Rdgs Polit
I would start with the shoes. There are square pegs on the back of the backing plates, which adjust the shoes out to the drums.
Turn them in as far as they will go without excessive force, back off one or two clicks, then the shoes should just barely touch the drums when you rotate them, then back off the pegs one click.
Then you can start on the linkage adjustments.
Each rod will have a threaded end, which should be almost fully retracted when the brake pedal is fully released. So that when you step on the pedal and move it a few millimeters, each rod begins to operate at the same point.
Loosen each locking nut, remove the clevis pin, then rotate the clevis end until it is in the right place, or you can also loosen the nut on the other end and rotate the rod, then put the pin back in. Work from each wheel first, then back towards the foot pedal.
10 Brakes.pdf (338.0 KB)
The parking brake linkage is different on my '38, so I’m not sure I can help there.
I found mine was all put together wrong by someone who perhaps followed the Mark IV instructions, or botched it all up somehow, anyway I had almost no brakes when I first tried them.
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Hi Frank,
Rob’s information is great. I had a problem with mine not being balanced properly and very poorly adjusted throughout the rods and links. Even if the shoes are adjusted correctly, the brakes will be poor, inefficient, and unbalanced if the rods are not set up correctly.
Always start at the drums and then adjust so that there is only slight scuffing and the drums still turn freely. I always stab the brake pedal a few times after I think it is just right and often there is a bit more clearance.
Start at the back and adjust the bellcrank per the book, then the rods and work forward - brake pedal - handbrake - front bellcrank. Make sure you can be as accurate as possible with the setback dimensions for the bellcrank static positions. The reason is that it is the only way maximum pedal power transfers to the drums. At maximum pedal force, the bellcranks should be just coming up to the 90° position, but not over. (As mine were). It helps if you can check this with someone pushing the pedal as hard as possible while you check their positions under full load.
Theoretically, when you set this up properly, you should never need to adjust the system again except for brake shoe wear. Remember that excessive brake lining wear is evidenced by longer pedal movement which pulls the bellcranks past the 90°, so reducing the brake force.
I now have very impressive brakes.
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Frank
Unless you have removed the drums previously and know the condition of the shoes and lining, my suggestion would be to remove the drums and check all is well and there is still plenty of lining material.
Then, if all is well, as Rob and Peter suggest, go from there.
Regards
David