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Discussion Topic:
Mechanical brake question
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FFracer |
01-12-2013 @ 3:29 PM
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Member
Posts: 62
Joined: Oct 2011
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Hey all, Been fighting these brakes for a while now. A real PIA, I have relined shoes, turned drums, did not arc the shoes. All wheels are adjusted for no or very minimal drag The cross shaft front & rear clevis's are directly over one another, adjusted the rods as per the ABC's of adjustment... The fronts ok the rears not so much. Front brakes are fine but the rears don't engage, the swing on the rear levers are MUCH longer than the front in fact about 1"+ of swing or free play before the shoe hits the drum. I have to shorten the rear rods to the point that the threads are completely buried in the clevis. What am I doing wrong, Is there some other adjustment at the moving end of the brake shoes (cam) I relined these shoes because I thought they were correct now I am wondering if where the shoe contacts the cam if there is a difference and that's the problem? Any Help?? Thanks, Chris Thanks, Chris
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supereal |
01-12-2013 @ 8:39 PM
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Senior
Posts: 6819
Joined: Oct 2009
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Back off the adjusters on the backing plates all the way. Block the brake pedal down about half way, then adjust the clevis on each rod at the wheel until the lining just touches the drum. This will equalize the system. Remove the block from the pedal and adjust each backing plate adjuster until the lining just touches the drum, then back off until the wheel is just free. Never adjust brakes by using the rod clevises after equalizing. Be sure all clevises and their pins are not worn, and that the cross shaft bushings are tight, and that the pedal bushing and rod to the cross shaft are not loose. If properly done, you should be able to slide the wheels in a panic stop. I learned this method in my Model A days.
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FFracer |
01-12-2013 @ 9:52 PM
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Member
Posts: 62
Joined: Oct 2011
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had never heard that method... I will try tomorrow and let you know . Thank you! Chris
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FFracer |
01-13-2013 @ 2:50 PM
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Member
Posts: 62
Joined: Oct 2011
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worked sorta. I have a problem drivers side rear. It requires allot more forward movement of the brake rod before the shoes hit the drum so much so if I try to adjust that rod at the crossbar I use up all the thread at the clevis. Something is wrong, I suppose I could 1/2 A$$ it by simply cutting the rod by about 3/4". I don't think those rods are easy to come by so cutting it is not an option. I pulled the drums everything that I can see looks fine, I compared the cams R&L sides there the same length, Both Brake rods measure 61.375" Frustrating!
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flatheadfan |
01-14-2013 @ 5:08 AM
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Member
Posts: 450
Joined: Oct 2009
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Hummm.....It seems like you have done everything except measure the drum diameter. You need a brake micrometer to accurately do this. Most brake shops should have this device. A drum that is excessively oversize would explain the excessive rod pull. Maximum drum diameter is 12.060" Hope this helps. Tom
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40 Coupe |
01-14-2013 @ 5:14 AM
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Senior
Posts: 1674
Joined: Oct 2009
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It may help for us to know what year is the vehicle. It appears to be 33-34 since their rear brake rods are 61 3/8" long. You may want to disassemble the LH rear brakes to see if something has worn. I believe the adjustment clevis yoke is at each wheel and not at the brake "cross shaft" bracket and lever assembly. The unadjustable "eye" end of the brake rod should be at the "cross shaft".
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FFracer |
01-14-2013 @ 7:34 AM
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Member
Posts: 62
Joined: Oct 2011
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I thought about drum dia. so I swaped drums from right to left... No difference. BUT I am taking the drums to NAPA they will mic em' for me. 40 Coupe, 33' cabriolet. Yea I am at that point, looking at the track Kit, springs, adjusting wedges ect. I was looking yesterday to see if anyone sells a complete rear brake backing plate rebuild kit. I did not know the rod clevis was at the wheel, I will make that change, kinda works out, now I don't have to yell for the wife to come out and spin the tire while I adjust... "Come on Spin it! But it's hard & i'm freezing" Ahhhh Good Times LOL! Checked Drum dia. there both at 12.060" Chris
This message was edited by FFracer on 1-14-13 @ 9:19 AM
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supereal |
01-14-2013 @ 11:00 AM
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Senior
Posts: 6819
Joined: Oct 2009
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Overcut drums usually don't prevent braking, unless the shoe contact with the drum is insufficient. The fix is to arc the shoes to fit the drum for the full length of the linings. There used to be machines for that purpose, but the linings can be carefull sanded by hand until they fit. Another consideration is the condition of the brake wedges. If you have the Green Book, you can find the dimensions of the wedges and other brake components on pages 30-31. Due to the geometry of the brake system, very small wear on the wedges is multiplied. As wedges are mostly impossible to find, we weld on material and grind it to reach the proper contour. If your drums are just .060 oversize, they should be usable. Replacement backing plates are available, but about $225 each. I don't believe they will help unless yours are damaged. I'd bet on poor contact between the linings and drums.
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FFracer |
01-14-2013 @ 11:40 AM
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Member
Posts: 62
Joined: Oct 2011
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I agree the reason for excess movement is the space between the shoe and drum. I have a edge sander so I could sand the shoes to fit. In fact I will check this before I put it all back togther. I am going to go ahead and replace the cams, adjusting wedges & the wegde dust caps. I found this and a few other things at Macs. Could not find the shorter fore and aft shoe springs anywere?? I also got some of those S/S cupped washers (Hub nut washer) for the lug nuts on my spoked wheels. The lug nuts were really sucked into the rim, really didn't look or feel right. As always thank you for the input, Chris
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40 Coupe |
01-14-2013 @ 4:00 PM
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Senior
Posts: 1674
Joined: Oct 2009
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Roy Nacewicz has some of the brake parts.
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