I have a vibration at highway speeds . The vibration comes every 2 seconds or so. The inside edge of my front tires are cupped a little. I had the tires balanced and it made no difference. I am going in for an alignment on Saturday and the shop I'm going to "trues" tires. Anyone had this done or have any opinions about the process? Tires are 245/18 Goodyear Runflats.

 

I'm trying to locate a shop in western New York that will do this. I had to replace one of my rear tires when my car was a year old, due to road debris damage. This replacement tire didn't wear at the same rate as my OE tires, and after a few years of driving, the OD of the tires had changed to the point that my posi unit wasn't happy. It thought that I was constantly making a turn. (symptom...warm gear oil smell after driving to or from work)

I'd like to get the "larger" tire cut down to the OD of the smaller one.



Yes, I know this sounds like a "BS" story, but I'm 100% serious!

 

Have you tried getting your tires balanced with a Hunter GSP 9700 Road Force Balancing machine?
Here's a link with more info:
http://www.gsp9700.com/

 

true the tires? Do you mean unmount and mount and rebalance each wheel & tire ? plus alignment.

Dont think you want to shave just a little off part of the tire.

 

When I had a little inside wear they swapped the front tires and did the alignment but he didn't call it trueing.

 

"Truing" tires involves-basically-rotating them against a sharp edge or abrasive surface to take off high spots. If you've got enough tread on your runflats to eliminate the cupping and still have sufficient tread depth you may come out all right. Of course, if I were a smarty-pants I'd tell you to ditch the run-flats and get new tires all around. Since your car, according to your profile, is a '97 I'm assuming the run-flats are not original to the car. Old run-flats are even more terrible than new run-flats--an acquaintance with a 20,000 mile 2001 did not realize how bad his tires were until I finally got through to him and he changed them. Age hardens those original C5 run-flats to where they get very poor traction, become even noisier and harsher-riding.

 

Between the years of 1973 and 1977 I sold mags and tires. Every so often a tire needed a lot of weight. The company rep came out to check the problem and brought another tire . The tire on the rim was turned 180 degrees and still needed alot of weight. The replacment tire balanced out on the same rim with little weight. The story the rep told me was that a tire shop in northern Wisconsin used a tire lathe and then balanced the tire. Of all shops on his route that shop had zero tire problems and very little weight needed to balance. Is there anybody with Bonneville experence on balancing for high speed to make our Corvettes safer at higher speeds ?

 

I've had this to happen on a non-vette>

If you have had a flat/leak and used a fix-a-flat stuff...sometimes it will settle and form a heavy spot inside the tire.

If this is the case,you will have to dismount the tire and clean it out.

\db2
Carolina

 

yes but they do not "true" the tire, they toss it for a new one if the tire is out of balance.

Balancing the wheel makes more sense .

I no longer balance my rear wheels. the rear tires will move an inch or more on the rim with hard use.

 

Sounds like You don't true high speed tires You do **** like that to 18 wheelers tires. Just buy a new set of front tires non-run flats and your problem will be gone.

 

I doubt truing the tires would help. Your vibration is only happening every so often and not continously. If the tire needed truing or resetting on the rim so it was mounted correctly the problem would occur on each rotation of the tire. At 60 mph your tires are rotating from 12 to 13 times per second. Balance affects the instantaneous rotation speed and will cause a slight variation off from the base speed. I suspect your problem is due to a slight imbalance between two different tires. With each one slightly out of balance they would have two slightly different frequencies which as the tires rotate would come in and out of synch and give you the intermittent vibration. Sort of like two engines on an airplane that aren't rotating at exactly the same speed. You can hear the harmonic come and go.

Bill

 

What he said ^^^. Tire balance is directily related to rotational speed (rpm). You are most likely seeing two tires on the same axle that are slightly imbalanced and slightly different diameter that get into sync with each other and then pass out of sync. Bear in mind that this can also happen when taking a turn or curve. The out of balance "spots" can coincide simply because the turning radius is different side to side. Take another turn and they no longer coincide.

As far as harmonics, they are most likely present but not necessarily a part of the problem. Harmonics are simply a multiple of the fundamental frequency. So on a spectrum, you would see a large spike at 1x (the fundamental frequency), 2x, 3x and so on. Harmonics generally show up with less amplitude than the fundamental frequency. On a car tire, I would expect to see a prominent 2x since the suspension is loose compared to a bolted down electric motor or similar.

With the stiffness of the corvette chassis and suspension, I suppose it's possible that 2 tires on opposite axles could cause the problem. I would think the in and out of balance would be very regular and predictable.

Where it me, I would have the 2 tires on the same axle balanced. While removed, I would see if they can check diameter.

Anyway, there's my two cents worth.

 

Don't know where exactly in Western NY you are but Mavis has a bunch of location in the area, you can see all of their locations here http://www.mavistire.com/ProductCart/pc/_locations.asp if you're still looking for a place. They do good work, I know a guy at one of their locations so I go there whenever I need work done.

 

As you saying that the have a truing machine at their shops? I now work part time for one of the "big box" auto parts stores, and I'm in the local Mavis shop 2-3 times a day, delivering parts to them. Never saw one of these machines on site, but then again, I never asked.....