Chasing down a vibration

[Matt_S]

I've been feeling a vibration coming through the chassis of my car on the highway recently. I started noticing it after getting new tires, but I'm not sure the tires are totally to blame. I lifted the rear of the car up on each side so that the wheel was just barely off the ground, then spun the tire. I was able to see that there is a little out-of-roundness. I imagine that a small degree of this is acceptable, but how much? I also was able to detect a small amount of warpage in my rear rotors. It's not visible, but you can feel it drag a little more in one spot when spinning the wheel hub. The same symptoms are true for both rear tires. I haven't checked the fronts, assuming that I'd feel a problem there in the steering wheel. Also, I've rotated tires, which changed nothing.

I guess I'm looking to see how much out-of-roundness is acceptable. I assume that balancing should take care of a small amount of that. Should I have the tires re-balanced or balanced in a different way? Could the small amount of warpage in the rotors be to blame, even though I feel the vibration when I'm not on the brakes? I'm not sure which direction to take and don't want to just start throwing money at it.

 

[paulo57509]

Since you started noticing the vibration after getting new tires, I would look at the tires first.

How is the tire inflation pressure? I've had tire installers grossly over-inflate the tires before.

Perhaps take the car back to where you got the tires and have them verify the balance. Have them spin them up before they remove the weights to verify that they are indeed balanced.

You might try swapping the wheels around; fronts to back, left to right, etc. to see if the vibration changes any. You might be able to isolate the vibration to either the front or rear of the car. Once you do this, swap either the left or right tire with the spare and see if the vibration goes away. I had a bent wheel on my '74 Camaro and I found it using this method.

How's the front/rear alignment?

I'd forget about the warped rotors at this point, IMO.

 

[Ugly3]

High speed vibrations can be really hard to find. There can be many many causes. Hunter has a "road force" balancing machine that will eliminate 95% of the problems and tell you if the tires have "hard spots", if the wheels / rims are out of round, etc.

Here is the Hunter web site: Hunter GSP9700

Good luck, I had a similar problem earlier this year - the problem ended up being the axle shafts.

 

[kenw]

it could be the phase of the unknown moon orbiting Pluto.....

before you look for complex and rare causes, let's apply some simple logic:

It started right after you had new tires installed.

what does that say???

"Could be something as simple as the tires were not balanced correctly in the first place. Generally, if you feel the vibration in the steering wheel it is the front end, if you feel the vibration in the seat it is the back wheels. "

bingo!

and it may take a few trips to some different tire balancing experts to solve it. Just because Joe the Tire Balancer says it is balanced don't make it so. No guarantees of course, but let's rule out the obvious causes first.

Hoare's Law of Large Problems:
"Inside every large problem is a small problem struggling to get out."

 

[Matt_S]

Update:

When I originally got the new tires, they told me the left front wheel bearing needed replacement. Them being a tire dealer (Belle Tire), especially considering I hadn't worked with them before, I didn't trust the diagnosis. It's been nagging at me ever since, though. That's why I asked if a bearing could do that.

OK, so I'm thinking this whole thing over this afternoon in light of all the good advice I've gotten so far. I call Discount Tire about the RoadForce balancing: $15/tire. Ouch. OK, I said I'm not just going to throw money at this, so that's out. Then that bearing thing starts nagging at me again. So I get home, lift up the left front and sure enough, it's bad. So I dropped that and lifted the right front. Nice and tight. Both rears are also tight, no play whatsoever.

So the next thought that goes through my head is "Well, Belle Tire was right about that bearing (as much as I didn't want them to be), and I can't eliminate that as the cause of the vibration, and if I bring it back to Belle, the first thing they're going to say is 'Well, you still have that bad bearing', and a bad bearing is certainly not helping anything, so I'd better buck up and replace it."

So I got the part from AutoZone, along with an axle nut socket (free rental) and some excellent instructions I found on clubgp.com and 45 minutes later, I had a new wheel hub.

My test drive showed a definite improvement. The car feels much tighter, but I'm still feeling a little something. The kicker is that it's hard for me to tell whether I'm feeling the road or the tires, though. The stiffer sway bars and rear trailing arms I recently installed make you feel the road a lot more, which makes it all that much more difficult to make a call one way or the other. Also, because of this recent suspension work, I'm confident that nothing else is loose, as I've just been in there. I was on a brand new stretch of concrete this evening and felt nothing. After I got back on some older pavement, I was feeling vibrations again, so I'm inclined to believe that I'm feeling the road, not the tires. I do have free balancing at Belle, though, so tomorrow I'll bring it to a different store and get them re-balanced. I'll update after I get a chance to test drive it.

I hope you're all able to follow my somewhat-rambling thought patterns. Thanks again to everyone.

 

[labman]

A long time ago, I had a lot of confidence in Belle Tire. Likely no experience with them in your lifetime. If you can feel a difference in drag on the rotors, I would have them turned. There has to be some runout or they would never push the pads back to release the brakes.

 

[Matt_S]

quote:

---

Originally posted by labman:
A long time ago, I had a lot of confidence in Belle Tire. Likely no experience with them in your lifetime. If you can feel a difference in drag on the rotors, I would have them turned. There has to be some runout or they would never push the pads back to release the brakes.

---

That will be my next step if the balancing doesn't work. When I was replacing the hub this evening, I noticed that the front pads are getting close and the rotors aren't in the best shape, either, so I might as well tackle those, and have the rear rotors turned (hopefully) or replaced while I'm at it.

 

[Matt_S]

quote:

---

Originally posted by Ugly3:
High speed vibrations can be really hard to find. There can be many many causes. Hunter has a "road force" balancing machine that will eliminate 95% of the problems and tell you if the tires have "hard spots", if the wheels / rims are out of round, etc.

Here is the Hunter web site: Hunter GSP9700

Good luck, I had a similar problem earlier this year - the problem ended up being the axle shafts.

---

Oh, great! Don't tell me that!

I like the suggestion about the balancing machine. According to Hunter's web site, there's a Discount Tire near me with that machine. I'll have to stop by tonight and see what we can find.

In the meantime, please keep the ideas coming. I do agree that the tires are the most likely suspect, but could something like a bearing cause this? I'm not hearing any noise, but is that a possibility?

 

[Ugly3]

Matt_S - I do agree that the tires are the most likely suspect, but could something like a bearing cause this? I'm not hearing any noise, but is that a possibility?

A bearing is a very remote possibility. More likely something is loose and allowing the wheels to bounce on the road. Worn struts, ball joints, even tie rod ends can contribute. Hard spots in the tires can do it, and tires out of round (and there are specs for that) can do it.

Could be something as simple as the tires were not balanced correctly in the first place. Generally, if you feel the vibration in the steering wheel it is the front end, if you feel the vibration in the seat it is the back wheels.

 

[Lumberg]

quote:

---

Originally posted by Matt_S:
Update:

When I originally got the new tires, they told me the left front wheel bearing needed replacement. Them being a tire dealer (Belle Tire), especially considering I hadn't worked with them before, I didn't trust the diagnosis. It's been nagging at me ever since, though. That's why I asked if a bearing could do that.

OK, so I'm thinking this whole thing over this afternoon in light of all the good advice I've gotten so far. I call Discount Tire about the RoadForce balancing: $15/tire. Ouch. OK, I said I'm not just going to throw money at this, so that's out. Then that bearing thing starts nagging at me again. So I get home, lift up the left front and sure enough, it's bad. So I dropped that and lifted the right front. Nice and tight. Both rears are also tight, no play whatsoever.

So the next thought that goes through my head is "Well, Belle Tire was right about that bearing (as much as I didn't want them to be), and I can't eliminate that as the cause of the vibration, and if I bring it back to Belle, the first thing they're going to say is 'Well, you still have that bad bearing', and a bad bearing is certainly not helping anything, so I'd better buck up and replace it."

So I got the part from AutoZone, along with an axle nut socket (free rental) and some excellent instructions I found on clubgp.com and 45 minutes later, I had a new wheel hub.

My test drive showed a definite improvement. The car feels much tighter, but I'm still feeling a little something. The kicker is that it's hard for me to tell whether I'm feeling the road or the tires, though. The stiffer sway bars and rear trailing arms I recently installed make you feel the road a lot more, which makes it all that much more difficult to make a call one way or the other. Also, because of this recent suspension work, I'm confident that nothing else is loose, as I've just been in there. I was on a brand new stretch of concrete this evening and felt nothing. After I got back on some older pavement, I was feeling vibrations again, so I'm inclined to believe that I'm feeling the road, not the tires. I do have free balancing at Belle, though, so tomorrow I'll bring it to a different store and get them re-balanced. I'll update after I get a chance to test drive it.

I hope you're all able to follow my somewhat-rambling thought patterns. Thanks again to everyone.

---

Matt. it's refreshing to see someoen using good logic and common sense when dealing aith automobiles. I wonder if I myself would have handled the problem as well.

 

[Matt_S]

Thanks for the compliment, Lumberg.

No real update yet. The Belle Tire I went to last night was very busy and it sounded like they already had enough work to keep them past closing, so I'll stop by again tonight.

I did, however, stop by Murrays and pick up some Bosch ceramic brake pads. $50 w/$10 mail-in rebate. I noticed the front pads were low when I changed out the wheel hub and I figure you can't beat that price for ceramic pads. I've got Bosch semi-metallics on there now and they've lasted 43k miles already with no problems, so hopefully the ceramic ones are of at least the same quality.

 

[Matt_S]

Well, I got the free balancing done. I heard the service advisor/sales guy instruct the tech to check the wheels for problems too. They came back and told me 3 of the wheels were out of balance, but only by 1/2 to 3/4 of an ounce. The car initially felt a lot better. It's still got that vibration on the highway, though, and I'm still conflicted as to whether it's the car or the road. My handling is as good as it's ever been, though, with the new bearing and balanced tires. The car feels super-tight.

Tomorrow I'm pulling the rear rotors to check the parking brake and see if I can tell if the inside surface of those rotors, which acts as a mini-drum for the parking brake, is out of round. I'm also going to put the front end in the air and see if I can spot any problems there.

Question: if I were to raise both sides of the front end, putting them on stands and assuming the car was held rigidly in place, and throw it into drive, would my tires spin normally or would the differential goof things up? I don't intend to spin them any faster than idle speeds. I'd like to do this with and without the tires mounted. My main intention is to check the axle shafts and CV joints for any wobble. Any comments?

 

[69 Riv GS]

quote:

---

originally posted by Matt_S:
Question: if I were to raise both sides of the front end, putting them on stands and assuming the car was held rigidly in place, and throw it into drive, would my tires spin normally or would the differential goof things up? I don't intend to spin them any faster than idle speeds. I'd like to do this with and without the tires mounted. My main intention is to check the axle shafts and CV joints for any wobble. Any comments?

---

I've done this in the past to help pinpoint noise/vibration origins. The tires will spin normally(same direction). To simulate a highway vibration you'll want to duplicate that speed.

As a side note: If your a perfectionist - keep in mind with the frame/engine cradle supported and the suspension unsprung that the half-shaft geometry will be altered, this in of itself could produce a very small amount of vibration while inspecting. Keeping the front suspension "loaded" is an option, although this is sometimes virtually impossible to safely accomplish do to lack of a good jackstand point on the lower control arms. But, if your able to, and decide to go this route just make sure the frame is also supported - and high enough off the ground, so in case a wheel suddenly became unsprung[jack slipped] it would still be above ground level!

 

[Matt_S]

Well, I've finally located the problem. It was indeed a bad tire, specifically the driver's side front. I wound up switching that tire with my spare and test drove it. The vibration went away. When I moved the spare to the rear, putting the driver's side front back in place, the vibration came back. I switched the driver's side front with the driver's side rear and it went away again.

So back to Belle Tire I go. I'll try to get both driver's side tires replaced, as the one that doesn't vibrate has an indentation in the sidewall. I don't know if it's a real problem or not, but it's still a defect as far as I'm concerned, so it should be replaced. I'll still be satisfied with at least the one new tire, though. I'll be calling them tomorrow to make arrangements. Wish me luck.

 

[Matt_S]

IT'S FIXED!!!!!!

I took it to Belle Tire today and they found problems with all four tires! Two of them were worse than the other two. So they warrantied all four tires. I wound up paying about $20 a tire to get them all replaced. Needless to say, this finally fixed my problem and I'm very happy right now. Thank God I can finally put this one behind me! Thanks to everyone for all the good suggestions I got.

 

[ediamiam]

I wouldn't be happy about paying $80 to have warrantied tires replaced. Especially when the problem started almost immediately.

 

[Matt_S]

I'm not so happy about having to pay $80, but I AM happy about putting this whole thing behind me.