Cyclical vibration over 65

[SithSolo1]

About a week ago I noticed a vibration while driving over 65ish. At first I thought it was the badly patched road I was on but its still happening on the smoother roads I'm use to. Its almost like the car shudders for 1-2secs and then its fine for the same amount of time then shudders/vibrates again, off and on until I drop back down below 65. I may still happen under 65 but I can't feel it with the butt-meter. It does it whether using cruise control or just my foot.

I'm the tires look ok on the outside though fairly worn and they are up to the correct inflation but I wonder if maybe one of them is damaged internally or if perhaps I threw a wheel weight and one is out of balance. Anything else I should look for before taking it to a shop?


Update - http://forums.anandtech.com/showpost.php?p=36573129&postcount=14

 

[satyajitmenon]

What car?

On some older BMWs, worn FCABs result in vibrations at a specific speed.

Could also be that one of the weights on the wheel has come off, resulting in an unbalanced wheel?

 

[SithSolo1]

2005 G35 coupe, auto transmission, ~80k miles

 

[MiataNC]

Vibration issues at 55-65mph are almost always a wheel balance issue. Look for missing weights or a bent rim (which creates a wheel balance issue)

 

[SithSolo1]

Ok, thanks. I'll update once its fixed.

 

[96Firebird]

Does it constantly vibrate if you turn left or right (say, to change lanes)? Sounds like what my Buick felt like when I had a bad wheel bearing because of an incorrectly balanced winter tire.

 

[SithSolo1]

Does it constantly vibrate if you turn left or right (say, to change lanes)? Sounds like what my Buick felt like when I had a bad wheel bearing because of an incorrectly balanced winter tire.

As far as I can tell, turning/changing lanes has no affect, only speed.

 

[phucheneh]

If the frequency of the vibration is 1-2 seconds, it doesn't sound like a wheel/tire. At 60-70mph, you would be getting the entire 'cycle' of noise/vibration multiple times per second.

I'd wonder if you aren't feeling something in the driveline, possibly being modulated by your right foot. Is this an AWD car? G35x's can have some pretty awful driveline vibration issues.

 

[SithSolo1]

If the frequency of the vibration is 1-2 seconds, it doesn't sound like a wheel/tire. At 60-70mph, you would be getting the entire 'cycle' of noise/vibration multiple times per second.

I'd wonder if you aren't feeling something in the driveline, possibly being modulated by your right foot. Is this an AWD car? G35x's can have some pretty awful driveline vibration issues.

Its RWD. I does it whether I am in control of the pedal or if the car is in cruise. During lunch I'll try to see if the RPMs are fluctuating when it happens and see if I can get more accurate timing. I had them check the Trans and Diff fluids back around 65k, they said they looked fine and probably wouldn't need changing until closer to 90k. Last time they were flushed was around 38k.

All that said its currently due for an oil change and needs new rotors/pads/brake flush.

 

[SithSolo1]

Ok, I finally found some smoothish road to drive on. The vibration is fairly constant at highyway speeds and increases in intensity as you accelerate above 60mph. I can't feel it below 60 but at 75 its enough to vibrate the rear deck, steering wheel, and dash. I used cruise control for about 6 miles round trip, rpms did not vary with vibration intensity. To me, it feels like its coming from the back half of the car.

 

[fbrdphreak]

This is the outlier, but take a look at the brake rotors to see if one looks different from the other. You should be able to do this with the wheels on. I had a stuck brake caliper that would only cause vibrations above 50mph. You would see more scoring or discoloration on the rotor or lots of brake dust on a corner with a stuck caliper.

That said, a wheel out of balance is your first likely issue. Then comes wheel bearings and/or alignment.

Take it it a tire shop and they should be able to figure it out in short order. Depending how long it's been since you had the wheels balanced and alignment checked, I would have both done as preventive maintenance.

 

[jaedaliu]

This is the outlier, but take a look at the brake rotors to see if one looks different from the other. You should be able to do this with the wheels on. I had a stuck brake caliper that would only cause vibrations above 50mph. You would see more scoring or discoloration on the rotor or lots of brake dust on a corner with a stuck caliper.

That said, a wheel out of balance is your first likely issue. Then comes wheel bearings and/or alignment.

Take it it a tire shop and they should be able to figure it out in short order. Depending how long it's been since you had the wheels balanced and alignment checked, I would have both done as preventive maintenance.

I had a scalloped tire once that I never bothered to rotate on my econobox. Replaced it and 100% repaired. Don't know if this is your issue. But I agree a tire shop isn't a bad place to start.

 

[CubanlB]

Having had a stuck rear caliper in a 2005 G35x, the vibration would be the worst when getting up to speed then get a bit better (in my experience).

G35s seem to have a lot of vibration issues, one thing to check would be the compression arms. The bushings go bad and throw the whole front suspension off a bit. Any clunking while navigating parking lots and speed bumps might be an indication of this issue.

I had my wheel bearings checked and one replaced this last winter and the vibrations remained. I guess the other bearing could have needed replacement, but wasn't bad enough to warrant it?

 

[SithSolo1]

Update:

The shop said the rear passenger side wheel bearing was bad and needed to be replaced.

 

[DaTT]

Update:

The shop said the rear passenger side wheel bearing was bad and needed to be replaced.

Did you notice an audible "hummmmmm" while the car was vibrating? Also a sign of a bad wheel bearing.

Is it fixed now?

 

[SithSolo1]

There was a "hummmm" in the past from that corner but no vibration, since the vibration started I hadn't heard the hum. Its still at the shop, I'm also having new rotors and pads put on all four corners and I'm getting new tires next week. Hopefully after all that I'll be set.

 

[DaTT]

The hum is usually a dead giveaway for a wheel bearing. Glad it's all sorted out now.

 

[SithSolo1]

Final update

Original work done:
Oil change
Replace rotors/pads on all four corners
Replace rear passenger wheel bearing and hub assembly

Results - Vibration still present, brakes much better, no droning sound from the rear while driving

Additional work done:
New tires on all four corners
Alignment

Results - Quieter ride, no more vibration

Rear alignment was out of spec and I was dragging the rear driver side tire resulting in the vibration. End up with some Michelin Pilot Sport A/S 3 tires so we'll see how long they last. I've only had one set that made it over 20k miles.

 

[SithSolo1]

oops