Drums out of balance?

[Dyn Blin]

This may be a draft question,  but do drums ever become out of balance as they wear?

After swapping out both when I rebuilt the rear sets last week, I drove it on the freeway tonight for the first time.   An annoying vibration I haven't been able to find between 45 and 55 is gone.

That's the only recent change to anything that would remotely affect driving.  U joints seem OK as part of of my overall attempts to track it down.

[Angelo Voltura]

The short answer is yes, they do. But the chances of you actually noticing or feeling it are next to none. You would feel a warped brake rotor first.

I would be checking your driveshaft. An out of balance driveshaft, which is possible especially after replacing u-joints, will cause an on/off vibration at cruising speeds.

I would doubt that brand new drums wore /that/ fast to cause amounts of vibration that would be noticeable. As someone who has 400k miles on original drums and does not have vibration from them, I would be skeptical.

However in your case they could have very well have been. Sounds like you've fixed the issue.

[Gary Lewis]

If you are saying they are new drums, then they may not have been balanced from the factory.  They won't wear very far out of balance, like Angelo said, but they may have gotten out of the factory w/o being balanced.

[ArdWrknTrk]

Drums can warp and then shoe action can wear them out of balance.

I'd tend to think there is a harmonic in the drive shaft as Angelo mentioned, OR you have a pinion engagement (backlash) issue.

This might show up at a certain road speed because there is neutral throttle.
Does it happen while accelerating, or braking through this speed?

[Whisler]

I read the OP as saying the new drums eliminated the vibration. Am I mis-reading?

[ArdWrknTrk]

In retrospect it seems you are absolutely correct.

I was following Gary's lead and lost sight of the OP.

[Gary Lewis]

Yep, I mis-read it.  My bad.   

[Angelo Voltura]

Glad I was not the only one!

[Dyn Blin]

Thanks gentlemen.  I got an unexpected shift and couldn't check back- thanks for the responses.  

Yes, the drums are the only recent change.   I've had 3 more freeway runs since the note and it's still smooth in that range.  

I kept the old drums.  I suppose I could put them on again and go for another run, or take them to get them turned and see if the shop can tell me anything.  

I keep expecting the vibration to come back, if it does, I'll update.

[ArdWrknTrk]

Please try not to expect the worst.
Having no expectation is better than raising your cortisol levels.

[RenoHuskerDu]

My master tech buddy has noticed a spate of inexpensive drums as sold on fleabay and amazon that are not round from the git go.

Encountered this myself on our Bully whilst fighting a lengthy brake issue. Bad drums was a root cause, but not the only one. I bought some name brand drums and that solved the grabbiness when cold.  Pulsing was only evident to the trained driver (not my driving daughters).