Rear Tire's cupping

[lakemeadzmonster]

Has anybody had any trouble with Nitto NIT555 Extreme Tire's cupping just on the outermost tread, identically on both sides?

( Factory size 315/35/17 and wheels).

They have about 6000 or so miles. It is just becoming noticeable.

Balance was checked, Shocks , Tire pressure 35 psi, bearings tight. :confused:

[csavaglio]

My new Z has the same tires, but they've only got about 7 or 800 miles on them so I haven't seen any issues yet.

Usually cupping in the rear is an alignment issue but it could be a worn or loose suspension part. Low quality tires could amplify the problem too, but Nittos are considered pretty good. I wonder if anyone's written any similar problems in Tire Racks reviews.

Chris

[WARP TEN]

My new Z has the same tires, but they've only got about 7 or 800 miles on them so I haven't seen any issues yet.

Usually cupping in the rear is an alignment issue but it could be a worn or loose suspension part. Low quality tires could amplify the problem too, but Nittos are considered pretty good. I wonder if anyone's written any similar problems in Tire Racks reviews.

Chris

Tire Rack does not appear to sell Nittos. I have been researching tires for a possible spring switch from Sumis. I would be interested if anyone has had similar problems with the Nitto 555s as I am considering them. -- Bob

[GOLDCYLON]

Has anybody had any trouble with Nitto NIT555 Extreme Tire's cupping just on the outermost tread, identically on both sides?

( Factory size 315/35/17 and wheels).

They have about 6000 or so miles. It is just becoming noticeable.

Balance was checked, Shocks , Tire pressure 35 psi, bearings tight. :confused:

Did you have the car thrust angle aligned and road force balanced? :cheers:

[csavaglio]

The Sumis aren't good tires at all....just a bad performing tire all around and, at least a few years ago, they used to use the same tread cap on the 315s as the 275, so you end up with a narrow contact patch. I had a set of rears on my '88 street/strip vette with 11" rear wheels. The only thing they have going for them is the price. I'd only consider getting them if I was getting rid of a car.

When I searched reviews, I didn't find anyone with cupping problems on them. I don't have enough miles on my set to give a comparison.

I agree with Cylon in that it's probably an alignment issue if the suspension, bearings and balance are good.

Chris

[RHanselman]

I just put new Nitto's on just about 50 miles ago. What a difference...

I would suspect you have a suspension alignment issue or you have some worn parts that allow the suspension to move (not as designed) for example dry rotted dog bone rubbers. I know mine are worn however I haven't had time to replace yet... I can feel the rear move when I take my foot off the gas with the clutch still engaged. Not much movement but it's there...

[GOLDCYLON]

The Sumis aren't good tires at all....just a bad performing tire all around and, at least a few years ago, they used to use the same tread cap on the 315s as the 275, so you end up with a narrow contact patch. I had a set of rears on my '88 street/strip vette with 11" rear wheels. The only thing they have going for them is the price. I'd only consider getting them if I was getting rid of a car.

When I searched reviews, I didn't find anyone with cupping problems on them. I don't have enough miles on my set to give a comparison.

I agree with Cylon in that it's probably an alignment issue if the suspension, bearings and balance are good.

Chris

Chris op questions was about Nittos. However we all agree the Sumitomos are crap.

[csavaglio]

I know, I only mentioned it because it was mentioned. Sorry for the off topic comment.


Whenever I see odd wear patterns, my first thought is alignment as wheel bearings and suspension components give other symptoms. The rear is very susceptible to alignment issues because some shops don't even bother to align the rear, don't know how to properly align the rear on a vette (the settings can change just by rolling the vehicle), or don't want to spend the time to do it properly.

C

[lakemeadzmonster]

Good thoughts from all, I will check those bushings Ron that makes sense, I really like the NITTO's,

Safety Heads up. I do like putting some weight in the back. It makes a huge difference in them 555's grabbing pavement, I had a bit of a scare when I first got them on a Hot Las Vegas day, I was trying to get over into the lane I needed and had to quickly change lanes before exit and the person behind me was on board but and when I did I got a fish tail I wasn't expecting at only 60mph or so. I recovered but you guys know the helpless feeling


The front tires I just put last week on are NITTO MOTIVO 275/40/17. New hub bearings, and a 4 wheel alignment, It feels like a new car again.

Maybe they changed something when it was aligned that will help in the future with rear cupping, I will stop by and check with them about it. It was only last week. J.

[csavaglio]

Putting weight in the back them will change the rear alignment on a Vette. Also, more weight and driving them hard will put a strain on the tires. That kind of stuff has been known to cause cupping. Nitto 555's are street, not racing tires....they're not meant to really be abused on a consistent basis. Years ago, when I used to autocross, there were a handful of guys running trucks. They're front tires would do that badly after a day of autocrossing.

As a side note, next time you buy rear tires, depending on how much you drive and what sort of weather you drive in, you may consider drag radials. They're a cross between strip and street tires....they're not the best at cornering, but you can definitely drive them in dry weather. They'll handle the abuse a bit better than most street tires.

C

[lakemeadzmonster]

To clarify, To get the best feel, I'm only talking around 100 pounds. If two adults in the car its not needed. Obviously the car was designed to have more weight in it than the driver.

The Goodyear Eagles had no cupping when I took them off a couple of years ago. I'm going to talk to Big O and see if they caught the issue with cupping and if the rear thrust angle was checked and if they forced balanced. Joel :)

[csavaglio]

Good luck. Let us know what they say.

Chris

[batchman]

If it's not worn parts, it's alignment.

Try more (rear) negative camber, bump it by 1/2 deg more negative or so.

Flip the tires on the rim so you can tell what the wear is doing.

A cheapie infrared pyrometer can tell you about what's happening after a 10 minute highway run.

Good luck,
- Jeff

[lakemeadzmonster]

The final word from Big-O Tire concerning what they did during the 4 wheel alignment.

The thrust angle I believe was off in rear according to the Tech who did it initially but I was not given the before and after findings the first day. So what I have is 2 Technician accounts verifying the rear was out of alignment when I brought it in which caused the cupping.

But minor enough the tire should wear back flat on outer treads. I had it checked and got a new baseline this time, with the correct setup the Z tracks great even on these bumpy freeways and I'm really happy with the NITTO Motivo front tires what a difference! Gas milage creeping back up. :-D


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