Randy Munson

1992 stock vette with 275/40-17 Sumitomo HTR-Z tires all the way around. Bought new chrome ZR-1 rims from OEM Wheels(forum member from Oklahoma), had them mounted and road force balanced. I'm getting a steering wheel shake at any speed over 60, and when I hit a non-smooth patch of road it feels like the front end shakes and the tires even come off the road a bit on occasion. New KYB shocks all the way around. Only 5K on tires. 34 PSI. NEVER had these issues with my stock sawblades. Someone mentioned something awhile back about Sumitomo's having a rough ride as compared to other tire brands(like Kumho). Can anyone verify this and/or suggest a tire that rides smoother than most. My vette is strictly a DD, not a track or drag machine. Ride quality is of utmost importance to me. I wonder if a 4-wheel alignment would help the steering wheel shake?

vader86

I've had Sumis for about a year and though they aren't the best for anything, I didnt notice any worse vibration.

onedef92

They can't be any worse for ride quality than the stock Goodyear Eagle GS-C's

Pttrader

I would have the balance rechecked. You might want to jack up your car and inspect the front ball joints, tie rod ends, and wheel bearings for wear. Years ago I drove IROC Zs and they had wider tires than stock and the GM parts wouln't hold up with the wider tires so I found out that using Perfect Circle and Moog parts kept the front end tighter longer.
I also question the high air pressure. On my rear tires I had to drop to 24#s to keep the rear end from sliding (Especially when there was sand on the pavement) around the corners. I have the 255s on my front but will probably go wider when the Michliens wear out.

Mccumb4

But they suck in just about every other regard except price. I can't wait until it's time for an upgrade. I'm thinking Vredesteins for the replacements. I'm running 315 35 17 on the back and 275 40 17's on the fronts.

onedef92

I also question the high air pressure. On my rear tires I had to drop to 24#s to keep the rear end from sliding (Especially when there was sand on the pavement) around the corners. I have the 255s on my front but will probably go wider when the Michelins wear out.

Did that kick your LTPWS light on? If my pressure drops below 25 lbs., my LOW TIRE PRESSURE light on my DIC comes on.

Weav's Vet

I have them but wouldn't know if they were rough or not. It's all I've had on the car except for the wore out run flats that were on it when I got it.

Randy Munson

Isn't 35 PSI the recommended pressure from the factory? Mine says it is. I did lower the pressure to 34 PSI last night. I'll keep lowering it 1 degree at a time(up to a point) till it feels more like I want it to. I'll take it back to Discount Tire and have the Hunter Road Force balance checked. I was also thinking of swapping the fronts and rears(same side) to see if it was a bad wheel, and having a 4-wheel alignment done. It's got to get better than what it is. The alignment would tell me if my fron tend parts(tie-rods, etc.) were bad I assume....

eagleye

I have Sumitomos on my 89 for the last 2 years and I can't find anything wrong with the ride. I have GY Eagles on my 93 and they don't run any better or worse than the Sumitomos on the 89. I have the stock rims on both cars. I actually think the 89 has a smoother ride than the 93.

Goldcylon

Get them balanced again, Summos wear out fast but their ride quality would not cause what you are described. Sounds like either you have lost a weight, Have a blem or ??? Id start with getting them balance and tracked.

Pttrader

I have increased my tire pressure to 29. I was experimenting because the Michelins were not original to the car and they had 35#s in them along with all the sand from this spring on the road the car would just slide around the corners.
The door sticker says 30 all the way around and that should be the optimum pressure unless your running slicks or high speed racing where I read somewhere to run higher pressure I believe 32#s. I never had any light come on so it maybe either I don't have that option or it's not working like the horn.
I know some tire places will put whatever tire pressure it says on the sidewall, but I usually like to run close to what it says on the sidewall.

Pttrader

Correction, usually like to run what pressure it says on the door sticker, sorry about the confusion.

Klondike

You might need to have them trued for roundness. It makes a world of difference. It makes them last longer too because the tread stays on the ground instead of skipping along. You can spin balance an egg, you just can't roll it.

Randy Munson

Are you refering to the tires or the rims or both? This was not nearly as bad with my stock sawblades before and the same Sumitomo tires....

jabez

For a smooth and quiet ride I would go with Yokohamas

cv67

Check the wheels to make sure they are good and straight.
Tires, try running a few lbs less, bet it rides better.

RandyJ75

I was looking for a smooth, quite ride, as the Goodyears on my car were noisy as hell. I went w/ some Nitto Nt555's, 285/40-17 tires. I am very happy w/ them. They ride great, and are very quite.

Randy Munson

What year vette? My door sticker says 35 PSI cold. 1992 coupe. I've got it down to 33.5 PSI, not much difference from 35 PSI. I guess I'll take it back to Discount Tire and have them double-check the Hunter Road Force balance job they did. Maybe transfer left front to left rear and see if any difference. Then I'll have a 4-wheel alignment done there or at the dealership. My local Chevy dealer DOES treat me well!

floridamale

35PSI would be for factory tires & wheels once you change that your kind of on your own to find the best fit for your car it will vary. The swap thing might work I would do one side at a time to see which one is causing the trouble

rickneworleansla

I wouldnt think tire quality is going to do what you are describing, unless you have a bad tire from the factory. How bad is the vibration? Like others have suggested I'd check tire balance, bearings, tie rods, and ball joints. I'm having the exact same issue that started immediately after a rim and tire swap over a year ago. I tried swaping a rim for a new one on the fronts looking for a bad rim. No luck. I havent really done all four though. The only thing I can see is that I had a problem before and the new rims and tires made it noticeable. I really need to swap out all 4 rims and tires at once to see if it goes away. I'm also on my second set of new tires now since it started. That didnt help either. I've been on three different road force machines at three shops. The last road force balance by a good shop got a lot of the vibration out but some is still there.