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.

Bad axle bearing or a bent axle comes to mind for me.

bent axle shaft?

Gonna have to put a dial indicator on the drum and shaft to narrow things down.

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.

As posted above, time to break out the dial indicator. I have used sections of steel strip bent cold. Clamp or bold the steel to a feature on the axle or housing and bend to get the indicator where needed. A hole and 1/4" bolt to hold the indicator. At least you can check the axle ends that way.

Also it sounds like you trust the machine shop. Still would not hurt to get the drums themselves checked or maybe find a known good drum to mount and check.

Is your differential housing bent?

Can you hear any noise coming from the housing, brake assemblies from this condition when out on the road?

I am having a similar problem with my 70 cuda and am wondering if it could be the axles. I did change my drums and it seemed to help some but when driving I can hear noise coming off the rear wheel area... it sounds like bias ply tires on coarse pavement but the sounds modulates - like a low tone version of what a brake drum lathe sounds like when it cuts a drum with a high spot. It seems to be more predominant at lower to cruising speeds. Also seems to go away altogether in at higher speeds.

Does that sound like bent axle(s)? New timkin taper bearings on both shafts. Original axle shafts were in OK condition. Car had been hit earlier in its life. Front RH and seemingly in the rear too. I never drove it prior to restoring it. Got it as a basket case.

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

New shoes - yes. It does not hop when I brake but that could be because it is affecting the rears only.

I had the same issue with a 92 v8 Dakota, turned out the drum was the problem. Put a new drum on it and problem was gone.

What wheels are you running? I had this problem years ago, the wheel was contacting the 'weight' that is spot welded to the drum and distorting the drum, knocked the weights off and problem solved, let us know how you go on this.

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.

im going to say its the shoes..bent axles on both sides? warped drums on both wheel sides?try different brand shoes..they are not made the same..otherwise wear them in and re-adjust..the high spots will wear down

Check the runout on the axles.
How is the drum to center register fit? It needs to be very close.

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

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.

Another thought...check the flat surface areas where the drum and axle flange meet. Could be something not letting the drum seat properly on the flange effectively making it wobble on the axle. Rust, metal burrs around the stud holes, etc.
That would explain the drum being good on the lathe but appearing bad when mounted.

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=D8NCBcsbNCA

http://www.youtube.com/watch?v=buVdvrEs0cQ

Here you can see how the axle isn't contributing to the wobble (I know sideways, sorry):

http://www.youtube.com/watch?v=MS5FoI0OV8Q

Sooooo... 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.htm

Unless there's some miracle chance of machining this out?

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

http://www.rockauto.com/catalog/raframec...l4068hfum1bdld4

On the specs... my car is an "E". I don't "think" there was any difference in important specs on drums for "B" and "E". Some were finned for cooling and some were not which affects outside diameter but not the "working" dimensions. I did double check the Y1 link and it is for 2.5" x 11". Good luck!

I finally checked my actual runout - one axle barely had .005", the drum (mounted normally, measured at the edge of the friction surface) had .038". The other axle indicated .012" – at that point I figured "close enough for now" and went and ordered some Challenger-spec drums from O'Reilly's. Hopefully when I put them on tonight or tomorrow that'll be the end of this mystery (otherwise Dr. Diff's getting more of my money for axles)

Check them to see if they are out of round before you use them.