Bad Brake drums?

[Hawker7]

I have a bad vibration between 40-60 MPH and tonight I tried to see if where it was coming from. I jacked up the truck and took the rear wheels off and run it up to 50 MPH and still had a bad vibration. I then took the drums off and ran it again and there was much less vibration. The drums are about 1 year old with 1k miles on them and I bought the them at autozone.

Has anyone else got drums that were bad? If I took them to a machine shop do you think there is anything they could do as far as balancing them?

[dmwphoto]

still have your old set to test this? Drums are pretty cheap but I have not seen them cause this. ya never know tho....

[ChevLoRay]

I think that removing the brake drums is probably masking the real problem. The speeds at which you say you have the vibration are more indicative of a driveshaft/u-joint issue, but that doesn't mean that it is the problem. I've personally had a vibration that was a bad rear shock, on one side. I've seen driveshafts that were not centered in the pinion mounting on the rear end. I'm not going to say your drums aren't the problem, but I've never heard of them causing a vibration.....but that doesn't mean it won't happen. Any imbalance in the driveline is going to be amplified by the sum of the components of the chassis. Have you run it with the tires/wheels in place, but with the vehicle elevated?

How are your bushings on the trailing arms? What about the center bearing mount if you have a 2-pc drive shaft? Shock mounting grommets good?

[Hawker7]

Originally Posted by ChevLoRay

I think that removing the brake drums is probably masking the real problem. The speeds at which you say you have the vibration are more indicative of a driveshaft/u-joint issue, but that doesn't mean that it is the problem. I've personally had a vibration that was a bad rear shock, on one side. I've seen driveshafts that were not centered in the pinion mounting on the rear end. I'm not going to say your drums aren't the problem, but I've never heard of them causing a vibration.....but that doesn't mean it won't happen. Any imbalance in the driveline is going to be amplified by the sum of the components of the chassis. Have you run it with the tires/wheels in place, but with the vehicle elevated?

How are your bushings on the trailing arms? What about the center bearing mount if you have a 2-pc drive shaft? Shock mounting grommets good?

I just went back out and put the wheels on without the drums and ran it back up to 60 MPH and there was no vibration, so I think it must be the drums.

[stich626]

Originally Posted by Hawker7

I just went back out and put the wheels on without the drums and ran it back up to 60 MPH and there was no vibration, so I think it must be the drums.

it might have tossed a balance weight they spot weld to the drums

[Gobbles]

Originally Posted by stich626

it might have tossed a balance weight they spot weld to the drums

x2.

I used to do commercial tires and any vibrations in a specific speed range were almost always balance issues. If there is no vibration without the drums I would expect a poor balance to be the culprit.

[Hawker7]

Well, I put my drums on a balancer and one was off by 13 ounces and the other by 9. One even had the weights put on the wrong side making it even worse. They were past being able to be balanced so I put them into the AutoZone junk category and a lesson learned.

I picked up two new drums from O’reilly's and one had no weights on it and was perfectly balanced but the other had a lot of weights on one side and was off by a few ounces. I figure that there is only so much weight they can put on due to lack of space so there must be a weight range they allow for it to be off. I just went back and got another one that had no weights and that one was close to perfect as well.

What a difference this made. I can now drive the truck over 50 MPH. Before the vibration was so bad I really couldn’t go any faster, but now it is as smooth as a new truck.

[passthebuck]

My dad told me that back-in-the-day you could get your wheels balanced on the car and in-situ. Makes sense to me if you don’t rotate your tires.

[68gmsee]

Originally Posted by passthebuck

My dad told me that back-in-the-day you could get your wheels balanced on the car and in-situ. Makes sense to me if you don’t rotate your tires.

Yeah. Back in the 60's I had mine balanced on the car. From what I remember, they would set the tire on a device with small rubber wheels that rotated the tire. On the wheel they attached a mechanism that the operator could turn as it was rotating until there was not vibration.

I've heard that some places still do it but I've never seen anyone in my area that does it. Not sure why.

[Sammy]

Originally Posted by 68gmsee

Yeah. Back in the 60's I had mine balanced on the car. From what I remember, they would set the tire on a device with small rubber wheels that rotated the tire. On the wheel they attached a mechanism that the operator could turn as it was rotating until there was not vibration.

I've heard that some places still do it but I've never seen anyone in my area that does it. Not sure why.

Ages ago the spin balance was considered the most expensive way to have them balanced. Fewer folks paid the additional money and used the then bubble balance cheaper method. But with the newer computer balance machines they use similar but more acurate tire and wheel balancing off the car/ truck.
The real issue is the quality of drums and why the drums were out of balance. I bought a set of new rear drums from O Rielly's stamped made in Canada. One of the two started getting cherry red after short drives. That drum wasn't true on the inside and had to have it turned true before it solved my problem. Quality of aftermarket drums is the real issue.