It is time to replace the tires on my 6 M/T coupe. For those who have switched to 245/40ZR18 front and 275/40ZR18 rear how are they doing? I am curious how the rears are on the 8" wide rim.


03 G35 Coupe 6 M/T

 

Thanks! I am trying to check with those who are already running these sizes.

03 G35 Coupe 6 M/T

 

Thanks for saying the same thing 3 times. My question is posed to those running the set up currently. I am quite familiar with the naysayers.

03 G35 Coupe 6 M/T

 

Lou,

Just because people disagree with you is no reason to bad mouth them. Rather then blasting people why don't you try to be positive and rather than saying don't do it or it is a liability why not share with the readers exactly what the issue is. If you check the 3 forums several are running the size I mentioned with no problem. If you could tell me and the others what the tire will do that is so dangerous that would be a big help.

Kirk

SAE Engineer


03 G35 Coupe 6 M/T

 

It would appear that there are a few naysayers with no practical experience running the setup who are opposed to the idea and several members on several forums who are running the setup with no problems. One is even a SCCA national autocross champ who drives the setup very hard with no problems. Tirerack even says it is ok to run the setup but they advise that the tire will not be at optimum performance by a marginal amount. They do not see a safety issue.

03 G35 Coupe 6 M/T

 

Here is one SCCA autocrosser who does have practical experience in over-tiring wheels. I drove a 2000 sports suspension Miata in CS/BS over the last 3 years. Originally, everyone was running 205/50-15s on the stock 15x6.0" wheels. Then Hoosier and Kumho came out with 225/45-15 tires and a lot of us switched. With the 205's and a properly aligned suspension, the car would actually be too loose so everyone was running a larger front bar. This is the setup that Peter Raymond won nationals in. After spending a year getting my car set up right on the 205's, I swapped to the 225's. Immediately the car pushed like a pig. I had to swap back to the stock front bar and completely change my tire pressures to get the car neutral. It took me another year fo tuning to get the car to drive normal again. The turn-in was drastically slower and I never really noticed a difference in grip. A lot of my fellow Miata racers were noticing the same thing. The first one to swtich back to 205s went 1 second faster than the field. Now, no one locally is running the big tires anymore.

I have taken several Evolution Driving Schools including Phase 1, 2 and 3 plus Dial-in. Dial-in actually explains why the 225's don't work better. Here is a simple question that answers everything:

If you are running a 205/50-15 and a 225/45-15 both on the same size rim and at the same tire pressure, which has the larger contact patch?

Right now, I am going to leave this question out here to see who knows the correct answer and follow up later.

04' G35 Coupe(finally in the garage)
6-sp Diamond Graphite/Willow w/Premium