Plasticman

03 convertible with automatic, essentially stock with non-run flat BF Goodrich tires on stock rims, Corsa cat back, Bilstein shocks, and Diablo tune.

Vibration is felt mostly in steering wheel and comes & goes at about a 3 second interval starting about 60 and does not change frequency, but does feel stronger at higher speeds.

Tires / rims were Road Force balanced, and it made no difference.

Looking for suggestions on where to look next. Will put it on lift and check CV joints, axles, bearings, etc., but I have done this in the past with no obvious clues.

Since it does not change in frequency, I don't expect it to be driveline related (but I have been wrong before).

I had a 93 GM Typhoon that did the same thing, and the rims were the issue (whenever the balancing was done, it was with mounting via the center hole, not the lug nut holes, and they were not concentric - new rims solved that problem), but I have not heard that C5 rims had the same issue (but another thing to check).

We just put on a couple thousand miles, and the vibration was the same before and after.

Thanks,
Plasticman

4DRUSH

What the hell is "Road Forced balanced"

Plasticman

Balancing technique by Hunter that applies a road load to the tire, as it is being balanced. Have used it with very good results on several vehicles.

http://www.gsp9700.com/

Plasticman

4DRUSH

Testimonials all say shops are saving money on wheel weights, hmmm wonderful

Plasticman

Your questions and comments are meant to give me bump? Thanks!

As I mentioned, I have several vehicles that the Road Force would work nicely (including a few that would not balance out with a standard balance job).

Besides, something I did not mention in my first post, the Typhoon vibration could be slowed or stopped while on an interstate curve in one direction (acted like it had balanced out), and then on an opposite turn it would increase in frequency (faster rate of surging). That told me it was tire or rim related. The 03 Vette does not do that, with the surging frequency never changing.

Plasticman

mrr23

you are about 1.5 hours from my shop. you can bring it to me to take a look at it. might be a wheel bearing, but i want to look at the tires myself. does the steering wheel move when the vibration occurs, or do you just feel it?

Plasticman

I would welcome another set of eyes on it. We will have to set something up. I am putting it on my lift this weekend, and we can go from there.

I just feel it in the wheel, no actual movement (just the pulsation, like going over a rough portion of road - every 3 seconds...).

Thanks,
Plasticman

firebirdfan

Just posting to see the results. My car is doing this right now at the 55-60MPH mark. Going faster or slower seems to help. It's in the entire body, not just the steering wheel.

It's also not RPM dependent. I can be in any gear and the pulsing is there.

It does seem to go away with temperature though. As the car warms up, it tends to go away.

I'm thinking it might be something with the balance of the tires or possibly the brakes. I haven't put new rotors or pads on the car yet.

Plasticman

It won't be until next week at the earliest that I get over there, after I check it out first (actually "again").

In your case, it sounds to me like typical tire/wheel balance, and I would start there first. Obviously (from my previous posts), I would balance it on a Hunter Road Force balancing machine. Could be just a simple "thrown" wheel weight.

Here is an excellant website that identifies most (if not all) of the possible vibration caused problems areas to check:

http://www.aa1car.com/library/vibrations.htm

Plasticman

Plasticman

Did an under car inspection (saw nothing "obvious"), inspected wheel bearing tightness, and took a "few" readings.

1. Tires are dated late 2007 & early 2008 and have ~15k miles. The depth across the tires is "not bad" and pretty consistant around (took reading every 90 deg. , and across at each of the 4 grooves). No cupping or feathering. Fronts are showing more tread in the center than edges (by about .020" to .030"), so I think I could boost up the pressure a couple of pounds. Rears are pretty consistant across the board.

2. Took rim lateral runout readings and saw .053", .020", .035", & .040".

3. Took rim radial runout readings and saw a max of .010" on worst rim.

4. Took rear axle shaft TIR readings, and see .002" (driver side) and .018" (pass. side).

I know the Vette was hit in rear pass. side area prior to my purchase (know rim & fender were replaced). So I suspect that the axle was bent during this direct side impact, and not replaced (CV joint boot appearance - age, and clamps, plus shaft paint finish appears to match opposite side as other indicators). The CV joints have very little rotational slop and are equal on both sides. Do feel any radial slop in CV joints.

Question: Is .018" TIR radial runout in the pass. side half shaft the cause of my vibration? I doubt it is the whole story (or maybe not even part of it), since the type of vibration I am feeling is caused by 2 (or more) imbalances going in and out of phase at a specific rate (like the difference between the diameters of the front and rear tires). But I will replace the pass. side half shaft anyway, since the CV joints may be damaged and be part of the issue.

Thanks,
Plasticman

Plasticman

Additional info on tires.

Max tread radial runout (with wide masking tape over the tread) seen was .058" (GM spec is .060" - pass rear).

I also saw a .055", also on pass. side (front).

Both on same side of car could be the cause of the pulsating vibration, since they are different diameters (and rotating at different speeds) which would allow them to go in and out of phase at a constant rate (depending on speed).

Max tread lateral runout was .035" (GM spec is .050", however that is for "off vehicle, and I measured mine "on vehicle - does not matter since way within spec.).

Plasticman

4DRUSH

If the tires were balanced under pressure, would the Road Force machine read those run outs?

Oh yea, BUMP

Plasticman

Yes, it did, but not the "same".
It shows a max. number of .022" for one rear tire (I can tell it was a rear due to the diameter shown), while all the others were .004" to .014".

Thanks,
Plasticman

mrr23

if you can make the time, we can recheck the road force balancing. even if it falls within acceptable range, they can still be force matched to lower the runout and orders of vibration.

4DRUSH

Bump

Plasticman

Sounds like a good plan. PM me with your address, contact info, and timing to meet your schedule.

Have a few "projects" the next few days, so it could be tormmorrow or Friday (or next week).

Thanks,
Plasticman

mrr23

How did it drive after the rebalance?

Plasticman

Robert,

The pulsing vibration is far less (still can feel it if I am "trying"). Given that the right side tires (especially the right rear), exceed the runout specs, you did a tremendous job and I thank you for your efforts and time. It was well worth it to to put it into your capable hands.

I will have to start looking for new tires (and new TPM sensors, since they are the original +12 years old units).

Thanks again,
John (plasticman)

mrr23

Hopefully its tolerable enough so you don't need to buy tires immediately. i know its a drive, but we can take care of your tire and tpms needs as well.

Plasticman

Robert,

No urgent need at this point, since it is very tolerable now! It is just that I know it is there (and the reason - which I did not know before).

What tires would you recommend that are relatively quiet non-run flats, with good wet weather performance, and "good balance" characteristics (well manufactured)?

Thanks,
John