I need to make sure these sizes will fit on my stock 06 enthusiast wheels (225/45/18 + 245/45/18) - 225/40/18 + 245/40/18
I got the guy to calculate it and I believe it came out to be a 2% difference.. But I am concerned because every tire calculator online doesn't calculate staggered setups.. (or am I just not using it correctly)?
If it is a 2% difference, is that too much?

 

You are going to lose 1" of tire sidewall on both the front and back, but at least the stagger will be the same.

 

But will my speedo and traction control be working well? Also, in an effort to not make another thread (I make too many, its disguisting), I'm just about to purchase Falken Azenis RT-615's. Can't afford the Goodyear GSD3's I wanted, or the Toyo T1R's. But are the RT-615's pretty sticky? My main thing is getting tires that are significantly stickier and better performing than the stock Potenzas, but I do not ever plan on tracking my car.. (maybe the drag strip, thats it).

 

I use the Rt-615's for auto-x and love them. I'd run 235/40 and 255/40 on the stock 18's. That will be closer to the stock diameter than the 225/40 and 245/40. There is a thread on page 1 of this forum about 615's and there are some pics of the 235/40, 255/40 set up on Nismo wheels. The speedo will be slightly off as the wheels will be underdriven, but should be no issues with traction control as the width/diameter stagger will be same as stock.

 

Here are some suggestions which will maintain a speedometer error of less than 0.5mph:

http://www.350zmotoring.com/modules....ex&name=Wheels

 

i as reading the link above and notice that they dont mention anything about 20s. i need to get new rear tires. right now they are 275/30/20. but i wanted to go a little thicker but i dont want to rub and i want to maintain an accurate speedo. i was thinking about trying a 35 profile tire. let me know