Rear brakes act warped cold & fresh from machine shop
#1638080
06/24/14 09:03 PM
06/24/14 09:03 PM
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Joined: Jul 2011
Posts: 817 Eugene, Oregon
Secret Chimp
OP
super stock
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OP
super stock
Joined: Jul 2011
Posts: 817
Eugene, Oregon
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I have 11x2.5 inch rear drums on my Coronet wagon and I can't figure out why they aren't running true.
Before taking them off to be machined & reinstalling them with new shoes, either wheel would catch on a higher spot on the drum when I tried to adjust them out, and you could feel the rear end pulsing under braking.
A couple years ago I took them off, had them turned, and threw them back on, still had the problem, but said "eh" as I wasn't driving the car like I do now. Back then the guy who helped me said it didn't even look like they'd been turned before
This time, the drums were machined to 11.059 and 11.060 by the same automotive machine shop here (not parts store) and immediately after bolting the wheels back on – car in the air, lugs hand-tight, both drums still dead cold and never used - the drums still don't drag evenly and in fact act almost the same as pre-machined, again.
I can't adjust the shoes out for slight drag because either drum catches on a certain spot as if it's warped. So right now I have slight drag across the area the shoes want to catch on and then they're too far in for the rest of the rotation. This still manifests if I have the wheels off (the wheels aren't warping otherwise-straight drums).
What could be out of whack in my rear end that would cause this? Or could the drums somehow just be off in a dimension that wouldn't appear on a lathe? Ordinarily I'd just throw new parts at this, but I can't find 11x2.5 rear drums for a decent price anywhere.
1967 Dodge Coronet Deluxe station wagon
1.03" T-bars, QA1 arms/rods, Cordoba/GM Metric/Volare brake & knuckle, XHDs, Hellwig rear sway, 318 Magnum w/ air gap, 727, 3.23s
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Re: Rear brakes act warped cold & fresh from machine shop
[Re: Secret Chimp]
#1638082
06/24/14 09:06 PM
06/24/14 09:06 PM
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Joined: Sep 2007
Posts: 14,889 up yours
Supercuda
About to go away
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About to go away
Joined: Sep 2007
Posts: 14,889
up yours
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bent axle shaft?
Gonna have to put a dial indicator on the drum and shaft to narrow things down.
They say there are no such thing as a stupid question. They say there is always the exception that proves the rule. Don't be the exception.
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Re: Rear brakes act warped cold & fresh from machine shop
[Re: Secret Chimp]
#1638083
06/24/14 09:13 PM
06/24/14 09:13 PM
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Joined: Jul 2011
Posts: 817 Eugene, Oregon
Secret Chimp
OP
super stock
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OP
super stock
Joined: Jul 2011
Posts: 817
Eugene, Oregon
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This happens on both sides, not just one or the other. I had been wondering if my axles could be bent or if the bearings are junk - when I got the car the rear end preload was pretty loose (like a good 3/4 inch back and forth). I knocked it back in to spec and it's still in the ballpark a couple years later.
1967 Dodge Coronet Deluxe station wagon
1.03" T-bars, QA1 arms/rods, Cordoba/GM Metric/Volare brake & knuckle, XHDs, Hellwig rear sway, 318 Magnum w/ air gap, 727, 3.23s
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Re: Rear brakes act warped cold & fresh from machine shop
[Re: Secret Chimp]
#1638087
06/25/14 09:23 AM
06/25/14 09:23 AM
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Joined: Jan 2003
Posts: 21,080 Niles , Ohio
therocks
oh wait.but hey.lets see.oh yeah.
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oh wait.but hey.lets see.oh yeah.
Joined: Jan 2003
Posts: 21,080
Niles , Ohio
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Did you change the shoes also?Ive installed new drums and shoes and found some with slight hi spots.They used to arc the shoes to the drums years ago.Now they dont as no one has the equipment.Does the car sort of hop when you use the brakes?Rocky
Chrysler Firepower
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Re: Rear brakes act warped cold & fresh from machine shop
[Re: Secret Chimp]
#1638091
06/26/14 01:01 PM
06/26/14 01:01 PM
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Joined: Jan 2010
Posts: 667 Los Osos, Ca
CKessel
mopar
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mopar
Joined: Jan 2010
Posts: 667
Los Osos, Ca
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See if you can scare up another pair of drums. Maybe a freind has a pair on his car to switch out. I know from working in the parts industry that you have to store drums laying flat not sitting verticle. If they have sat verticle, they can get egg shaped. Rotors are not as touchy. Something else you can try is to put them on inside out to check with a dial indicator. May not work well though if the center hole is a loose fit on the axle center pilot stub.
Carl Kessel
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Re: Rear brakes act warped cold & fresh from machine shop
[Re: Secret Chimp]
#1638094
06/27/14 09:39 AM
06/27/14 09:39 AM
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Joined: Jan 2003
Posts: 21,080 Niles , Ohio
therocks
oh wait.but hey.lets see.oh yeah.
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oh wait.but hey.lets see.oh yeah.
Joined: Jan 2003
Posts: 21,080
Niles , Ohio
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I had one at work that I did new drums etc on.Used hi buck Bendix drums.Went for a ride and when I hit the brakes it felt like the rear was coming out of the car.Replaced the drums and problem was gone.Sometime the shoes arent centered also and it will cause a drag on hi/low spots.Drums can have a hard spot also even if they were turned.Rocky
Chrysler Firepower
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Re: Rear brakes act warped cold & fresh from machine shop
[Re: therocks]
#1638095
06/27/14 12:50 PM
06/27/14 12:50 PM
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Joined: Jun 2005
Posts: 5,112 Western Md.
skicker
"The Champ"
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"The Champ"
Joined: Jun 2005
Posts: 5,112
Western Md.
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Sounds to me like 1 of maybe 2 things. 1st would be that the center hole in the drum is larger than the axle flange and is no longer hub centric. 2nd as previously mentioned the axles could be slightly bent. I would flip the drum over on the axle (install it backwards) and check it for run out.
...FAFO...
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Re: Rear brakes act warped cold & fresh from machine shop
[Re: nomore65BelvJim]
#1638097
06/29/14 12:38 AM
06/29/14 12:38 AM
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Joined: Jul 2011
Posts: 817 Eugene, Oregon
Secret Chimp
OP
super stock
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OP
super stock
Joined: Jul 2011
Posts: 817
Eugene, Oregon
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Fun developments! I knocked my left drum off and the axle flange itself runs dead true. I put the drum back on backwards to see how runny-outy it was: http://www.youtube.com/watch?v=D8NCBcsbNCAhttp://www.youtube.com/watch?v=buVdvrEs0cQHere you can see how the axle isn't contributing to the wobble (I know sideways, sorry): http://www.youtube.com/watch?v=MS5FoI0OV8QSooooo... bonus points for everyone who guessed the drums vs the axles. They are mounted against a spare set of nuts screwed down all the way, not against the flange (would not sit flush backwards). Any tips on where to look for 66-74 11x2.5 rear drums? I can't even find them indexed in most places I usually shop (Summit, RockAuto, Jegs, Amazon). I've only located one vendor – they don't offer actual part numbers for cross-reference and they want $120 apiece: http://www.jimsautoparts.com/brake.htmUnless there's some miracle chance of machining this out?
1967 Dodge Coronet Deluxe station wagon
1.03" T-bars, QA1 arms/rods, Cordoba/GM Metric/Volare brake & knuckle, XHDs, Hellwig rear sway, 318 Magnum w/ air gap, 727, 3.23s
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Re: Rear brakes act warped cold & fresh from machine shop
[Re: ahy]
#1638099
06/29/14 01:16 AM
06/29/14 01:16 AM
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Joined: Jul 2011
Posts: 817 Eugene, Oregon
Secret Chimp
OP
super stock
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OP
super stock
Joined: Jul 2011
Posts: 817
Eugene, Oregon
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Quote:
I got a set of 11x2.5 drums a few years ago from Year One (E). Looks like they still carry them. Rock Auto has some also (4 left on the one I looked at).
https://www.yearone.com/Catalog/1966.74....s/rear-.-e.body
=0&ck[idlist]=0&ck[viewcurrency]=USD&ck[PHP_SESSION_ID]=ooomu6q5omrl4068hfum1bdld4]http://www.rockauto.com/catalog/raframec...l4068hfum1bdld4
Cool... maybe. These don't exactly match when they have specs, so this is where I'm unclear about things I can ignore and things I shouldn't.
I looked up the Bendix PDR0365 they had listed there, and they only x-reference it for 69 and up B-bodies. I measured my drum vs this one and there's about a half inch in overall height (depth?) difference - 3.9 inches for mine vs 4.4 inches for the new one.
I dunno if that means nothing, if they're going to hit my backing plates or be misaligned with the shoes, etc.
YearOne also only lists 10 x 2.5 drums for B-bodies. Did you use E-body drums in a B yourself?
1967 Dodge Coronet Deluxe station wagon
1.03" T-bars, QA1 arms/rods, Cordoba/GM Metric/Volare brake & knuckle, XHDs, Hellwig rear sway, 318 Magnum w/ air gap, 727, 3.23s
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