Hey, a while back i had posted pics of my car. And even though i havent seen it in person (in iraq). I want to go ahead and get new rear tires. A few questions i wanted to ask before i do it. As of now it has 245-45-17 in the front. And 285-35-18 in the rear. The reason im not happy is the sidewalls are so thin in the back, the wheels look bigger in the front. I was thinking of going 285-40-18 in the back, or 285-45-18 if i can find them. Anyone think i would have wheel rub problems? My last question is my biggest one and its two part, does the speedo read off the front wheels or the rear? And even though i have my car madz28 tuned, i have a hypertech progammer i dont use, would it be possible to use it just to calibrate the speedo by tire size and it wont mess up the rest of my tune? Thanks in advance.

 

im running 275/40/18 in the rear and they rubbed all the time when i hit even little bumps so i took the wheels off, beat in the wheel wells where they were rubbing w/ a rubber mallet, re-sprayed it with rubberized undercoating, threw the wheels back on and they didnt rub any more, not sure if itd work with even wider tires though

 

A 285/45-18 is likely to be a problem. That's a 28" tire, and will just barely fit in the wheel opening. Its going to make the drivetrain feel like you put much (numerically) lower gears in the car..... for example running 3.42's would feel like you swapped in a set of 3.12's (if there was such a gear). 285/40-18 is a 27" tire, and would definitely present less clearance problems than the 285/45's. Both tires will give the car a "rake" with the rear end sitting higher than the front end.

The speedo is driven off the VSS sensor on the tailshaft of the tranny. Hence, the speedo reading depends on both the rear wheel tire diameter and the differential gear ratio.

 

Well, im pretty proud of myself, been doing alot of research and math, i think i figured out what should look good. So heres what i figured out. My current rear tires are 285/35-18s, which gives me 25.85" tall in the rear, and the sidewall is 3.92" tall. The current front tires are the 245/45-17s which is 25.68" tall, and a sidewall of 4.34".
So i figured this sounds good, 245/40-17s for the front which will be 24.72" total height and a sidewall of 3.86". I think this is what i should go with so i can get the aggressive look and i like the low profile tire look, thats not too little sidewall is it? I dont want to ruin my wheels cause the tires are too short.
The only other problem is the ones i want are nitto 555s, but i cant find that tire in that size, just a nitto invo, i want to stay with at least the same brand.
Any critizing or more suggestions would be great. I want my car to look good before i go home next month.

 

Well i went ahead and ordered the nitto invo 245/40 -17s, i cant wait to see them. When they get on ill post some before and after pics.

 

The "visible" part of the sidewall will be about 1/2" less than your calculated height of the sidewall. That's because the tire "size" (e.g. - 17") is calculated from the inside diameter of the tire bead, where it contacts the rim. The flange of the rim, that holds the tire bead on the rim covers about 1/2" of the sidewall.

You have to decide it you want the front of your car to lose about 1/2" ground clearance, and open up the gap between the outside diameter of the tire and the fender opening by another 1/2"