So I have had my g35 Sedan for over a year now, I got 18,000 out of the tires. I have lowered it on H&R springs with no camber kit. I wore out the fronts so I replaced them with the same size that was on when I bought it 255/40/18. Is this too wide for my stock 18" sedan wheels?

The rears I had the tire shop flip on the rims bacause of the excessive wear due to excessive camber/toe. The tire shop pointed out they car cupped. Now I have seen another "cupping" issue that looks totally different than what I would call cupping. On my tires the inside of the tire is dished in, concaved like. The middle is worn more than the outsides, I realize most people would say that the wear is due to "overinflation" but, I know for a fact these are not overinflated. 32 PSI cold is the most they would see.

The tire shop put new tires on my rear and took the rears and put them on the front, I requested that they flip them so I could get more life out of the inside tread. I drove 5 hours today and the car was all over the road, upon further inspection the tire shop had 42psi in the tires, I aired them down to about 35 because they were warmed up. This helped the quickness of the steering but, when I got on the interstate, it was still darting around when I was going totally straight, One other problem was that the "slip" light was coming on and affecting my driving around high speed corners! I was freaking out a little.

I got to my destination and inspected my tires, the middle was contacting the road as well as the shoulder, the two inner rows of tread were NOT contacting the road, I would describe this a "cupping" but, the middle is wore so I dont know what you call it. If you look down at the tire tread you can see that it looks like a roller coater ride, when it should be stright across!

Sorry this is so long but its weird ****,

 

To begin with most tire manufacturer's recommend a 8.5"-10" rim width for a 255/40/18 tire. You didn't say what year sedan you are running. If you have the 05/06 18" Sedan sport rims, they are only 7.5" wide. If you have the 07/08 rims then the fronts are also 7.5" wide.
So that could be some of your problem.

 

Ya I have an '05 so 7.5 is prolly too narrow of a wheel. The problem is that I already bought two new 255/40/18s. I guess next time I'll go to a 245... but not sure if I should go 40 or 45 series. The problem I have found is that a 245/45 is a 1/2" taller and a 245/40 is a 1/2" shorter than my 255/40 ...

 

If the car isnt lowered then i'd go with a 245/45 all around. Stock is 235/45 so 245/40 will be a little shorter and make the car look like it is higher than stock.
-GP-

 

One other thing is that the front tires didn't do this, they were a toyo t1r and the rears are a bfg kdw. So maybe this only happens on the rear?

 

the car is lowered on H&R springs

 

Well your VDC is going off because you mixed brands of tires... same thing happened to mine when i had stock michelins on the front and Bridgestones on the rear.

Cupping is when the outsides of the tires are "choppy" one block of tread wears down the opposite way of the next block.

When was the last time you had an alignment done?
-GP-

 

Your stock tires would have been 235/45/18 so if you wanted to go one size bigger than 245/45/18 would be the best choice. Your stock tires were 26.3" diameter and the 245/45 tires are 26.7" diameter. If you went with a 245/40 then it is 25.7" diameter.
235/45/18 = 26.3" (stock size)
245/45/18 = 26.7"
245/40/18 = 25.7"

 

Good points.

 

alignment was about a year ago.

Cupping is not what I have, not sure how to describe this problem.

I have had differnet brand tires for the last year and a half with no issues on the VDC.

I'm sure this problem is due to the F'd up BFGs, when they were on the back I dodn't notice the problem but, now that they are on the front its a HUGE problem.

BTW thanks for all the support and ideas, an alignment prolly wouldn't hurt. I think I may get some a-arms before I get another alignment though.

 

Had the tires put back on the rear today. The tire shop told me they could only put two new tires on the drive wheels... when you only replace two. Its the LAW.. WTF! They would put f'ed up tires on the front of a high perf. car, knowing they are F'ed up! This is one more example of our law makers injecting their total stupidity into our lives!

This was one of the most dangerous cars I have driven in a while, especially when the tire shop had my tires aired at 42psi!!!!! I have the F'ed up tires on the rear and she's stable once again.

Thanks to all who helped

 

I run 245/45/18 on my stock sedan rims and they wear in the middle faster than the shoulders. I normaly run 32 psi. In my case I think it is because I spend most of my miles on the highway. I was thinking about going back to the stock size to see if they wear differently but I have been happy with the 245/45's.

I think they slow the car down a little bit, but they have worked well for me overall.