Brake drum balancing?

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I recently replaced all the rear brake hardware on my Taurus (wheel cylinders, shoes, springs, drum, etc). Since this is my wife's car I rarely drive it, just the occasional test drive to make sure everythings working OK. Well, I took it out on the highway awhile back and I noticed a bit of vibration around 65-70mph. I thought it was a tire/wheel balance problem so off I go to Tires Plus for the free lifetime balance/ rotation bit (bought the tires there). It still didn't solve the problem. It feels like the back end is shaking/ vibrating but I can't confirm it. Is it possible the drums are causing the vibration? I no longer have the old drums so I can't verify that's the problem. Any ideas? BTW- the drums were purchased at Carquest and were made in Argentina.
 
I've had rear wheel alignment cause the condition you're describing ..but it reasons that it this wasn't there before and it's there now that the drums may need to be trued.

Here's the thing. This was recommended even back in the 70's. Brand new drums were out of round ..at least according to our drum cutting machine in class ....but SO WAS THE BOLT PATTERN in relation to the center hole. The lug holes would be rotating in a elliptical pattern that matched the out of roundness of the drum.

That is, it appeared to me that there was always some casting shift that was out of spacial relationship with the center hole. We even put dial indicators on the shaft to assure that it wasn't the cause.

So, I pondered if we just made the drums out of round by using the center hole as a point of reference. I guess it would depend on the clearances ..or how much slack each had (center hole vs. lug pattern) in fitment.
 
Originally Posted By: Gary Allan
Brand new drums were out of round ..at least according to our drum cutting machine in class ....but SO WAS THE BOLT PATTERN in relation to the center hole. The lug holes would be rotating in a elliptical pattern that matched the out of roundness of the drum.


Both, my Chevy and my Buick had that problem. Back then I thought it was a fluke, but now I realize it was totally normal. Thanks for clarifying that.
 
So, would I have to get a new set of drums to solve this? Or could a machine shop fix them? I suppose if the lug pattern were off they couldn't be trued. My wife says she doesn't notice the vibration (OK-OK let's hear the jokes
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) so I'm probably just going to leave it.
 
Originally Posted By: road_rascal
So, would I have to get a new set of drums to solve this? Or could a machine shop fix them? I suppose if the lug pattern were off they couldn't be trued. My wife says she doesn't notice the vibration (OK-OK let's hear the jokes
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) so I'm probably just going to leave it.


I dunno. I guess they could assure that the center hole was centered in the casting ..and do an offset enlarging to put it where it belongs. If the lug holes are out of whack ..then I think you would be back to the same situation after wearing in. They could assure that the lug holes are equidistant from the center hole and then offset enlarge the center hole to that point of reference ...but if that's out of whack with the casting ..then you've got another problem. The brakes and drum will wear perfectly ..but the thing may be so off center/eccentric that it creates its own imbalance.

I feel like Tyrell telling Roy Battey the multiple complications in giving him "more life" in Bladerunner.
 
New factory drums have balance weights welded on, so there is a chance balancing is to blame.
But being so close to the center of rotation, I doubt it.
Out of round drums are more likely.
Even more likely are tires that are imperfect.
Also, front brake rotors could be the problem.
If you haven't driven the car for a while at those speeds, maybe they were bad before the brake job.
 
I did the front brakes last year and I did take the car on the highway and it rode just fine, which is why I now suspect there's something (possibly) wrong with the drums. I guess there could be a problem with the tires, but Tires Plus checked everything out twice. Like I said, I'll probably leave it alone unless my wife complains about it. Right now I'll keep an eye on the tires and see if any strange wear patters develop.
 
"BTW- the drums were purchased at Carquest and were made in Argentina. "

No warranty? Think the first thing I'd do is pull them and return for replacement.

Bob
 
How about the wheel bearings? My Outback made a "wobba-wobba" sound from the rear at certain speeds that I thought was either the differential going bad, or an out-of-balance tire. Turned out that one of my wheel bearings had gone bad.
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I've always chuck up my brake drums and disc's in an engine lathe and have had to touch every one up just a little bit. I think it makes a difference. And you're right check the bearings too. Also make sure that the brake shoes make full contact with the drums and arch them in if needed.
 
Jack up the back and check the tires for out of roundness, they can be balanced but still not round. Easiest thing to do and IMO most likly.
 
Only drum I've ever seen that needed balanced was off the park brake assembly mounted at rear of transmission on a large motorhome. These are a mehancally activated drum brake assembly with backing plate secured to transmission tailshaft,drum installed as part of driveshaft, turning at driveshaft speeds. This particular one had been driven with parkbrake ON and wharped. We removed it,resurfaced to elimimnate wharp, then mounted to wheel balanacer (in static mode) and spun up to determine how much balast to weld back to exterior of light spot.

Bob
 
Originally Posted By: Tom_T
Jack up the back and check the tires for out of roundness, they can be balanced but still not round. Easiest thing to do and IMO most likly.


I've had this occur. It's hard for some to understand. The tire was just deformed. It was balanced perfectly. We're having the same problem in perception here. The drum can be in perfect balance ..yet be somewhat rotating on an eccentric. It can also be out of balance and spinning just fine.

Quote:
Or, have the tires balanced "ON" the car..


I haven't seen an on the car balancer in over twenty years. They were great in that you would balance the entire rotating assembly. There appeared to be an evolving campaign against this process in most of the para-trade recommendations. Recommendation after recommendation was always bracketed by "off the car". I think it had more to do with the skill required to operate the machines and the (perhaps) risks involved as opposed to the caged/shielded machines we have now. They too have evolved from high speed rotation to a crawl.


One thing that I know. If ever I have cause to buy drums again, I'm going with a caliper and check to see how everything relates in the casting. I may find out that YMMV between what's on the shelf.
 
i had a drum off my dads dodge ram 2500 truck. the truck had a vibration at high speeds that nothing would fix. i finally took the rotors and drums off and put them on the tyre balancing machine to check.
the machine has 2 modes for balancing things. static and dynamic.
dynamic is for tyres and wheels. static is for things like drums and rotors, motorcycle tyres, airplane props, mower blades, etc.

one of the rear drums was 9 ounces out of balance. 9 freakin ounces! i couldn't believe it. i ended up welding odd nuts and bolts to the outside of the drum until i got it overcompensated. then i use a angle grinder to slowly remove metal while re checking the balance. finally i got it zeroed in (well the machine is only a 1/4 oz sensitive so its pretty close.).
the remaining drum was an ounce out, and the 2 rotors were half ounce out each.

after balancing the wheels, tyres, drums and rotors, that truck ran so smooth at 75mph it was unbelievable. my dad has always thought the truck was just overly sensitive to the road. turns out it just had american made junk for rotors and drums.

9 ounces guys. thats ridiculous. but we spun some new drums from napa and they were a few ounces out too! plus i noticed what someone else had said about the drum wobbling. i don't think they machine these things very good , maybe the machinists are always drunk?

9 ounces! ill never forget that one.
 
When I had my 1970 Torana with 4 wheel drums, the drums had balance weights welded the the flat faces of the drums. Just checked my 2003 Nissan, and it doesn't...they are rivetted.

It's got me wondering on which centres these aftermarket kits are being machined and checked.

I'm not a machinist by any stretch, but you should'nt change the references during the machining unless absolutely necessary. Raw casting into external 3 jaw chuck to get centre bore. Centre bore to get PCD and Drum ID. Centre bore to balance.


Gary, the on car balance machines left favour down here as people needed to rotate tyres, include a spare etc...people found that after a rotation (or even remounting the same wheel in a different stud location) vibration could be bad.
 
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