A definitive answer to the following question would be nice, but an educated guess would be OK too.

I am getting 18" wheels; as noted in s2ki FAQ, tire sizes should be 225/40 in front, 255/35 in rear. However, the tires I want to get (s-02 PP) only come in 225/35 for the front.

The potential issue I see for this size is the difference in diameter between the 18 and the stock 16 front (diameter for rear 18 and 16 stock are almost the same). The 225/35 dia is 24.2; stock front dia is 24.9 - over 1/2 inch difference!
Also, rpm for 18 varies a fair amount from stock 16. Do odo and speedo come off front tires? If so, seems like there would be errors in speed & mileage. Also, wouldn't the front of the car be slightly lower than the rear?

 

Still can't understand why people go to +2 on the Stook? Tire compliance is all but eliminated. If it's not a track car your money would be better spent elswhere..........

 

Sounds like your best bet is to leave the damn car alone.

 

How about asthetics? Not all mods are for speed and performance... I am adding 18" Workmeisters because they are gorgeous. If the person wants to individualize his car, let him!

I have ~ $25,000 in mods in my car, about 1/3 - 3/8 of it are for speed/performance the rest is just for fun.

A lot of people buy cars to modify/personalize them as a hobby. I bought the car solely for hobby/modifying myself.

Just defending the guy...

Back to the discussion: the speed comes off the transmission in the form of the VSS (vehicle speed sensor) connector... So the rear wheels would be those that affect the speed. My recommendation: keep the wheel circumferance as close to stock as possible. I'm going 225/40 18 in front and 265/35 18 in back (not taking my own advice in the rear ). A really cool tire size calculator that someone posted here before:

http://www.miata.net/garage/tirecalc.html

It's posted by a Miata site but tires/wheels are tires/wheels...

 

thank you shaner:
you're worse than I am - I'm only getting $14K in mods (including the comptech SC)

maybe I'm a fool with more money (or at least credit) than sense, but this is something I want to do. At least I want to understand exactly what I am doing and what the potential ramifications are. And personally, I don't particularly like how the stock wheels look. And I like the look of big, fat meats on a car.

I know the ideal front size for the rims I am getting is 224/40, but I can't seem to find a well rated tire that has both 225/40 and 255/35 sizes. That's why I want to know if it is a bad thing to put 225/35 on the front.

 

285/30-18's are dead nuts.

 

I went with 265/30 & 225/40 on my 18" Workmeisters. They look great. I haven't got them on the car yet but Comptech said they don't rub on their's.

 

I'm VERY new to tire/wheel talk...so correct anything I say that is wrong. I'm assuming that the most important thing is that your tires/wheels give the lowest difference in speedometer readouts, and that the stock vs. after market set up has roughly the same #'s in regards to Radius, Diameter, Circumfrence, and Rev/mile.

If my assumption is correct, with that Tire Calculator...I see that the closest to stock #'s given come from the following tire sizes:

Front: 215/40/18
Rear: 245/35/18

Keep in mind stock sizes of 205/55/16 for Front and 225/50/16 for the Rears.

Again, I'm TOTALLY new at this...so excuse any of my ignorance. But after playing with that calculator for a while, I find that the closest to stock figures comes from these sizes. If you find something better...please do tell!!

 

Besides the sizes, I really hated the PP's they really hampered the cars handling, it got better with wear but when I put on the new ones. OMG it may be a tick better than stock! My latest set of tires is the Bridgestone RE-730
the 245/45 r16's are actually about a half inch wider than stock SO-2's (rear)

Tirerack has good spec charts for most tires so you can compare overall diameter and tread width. I think its suggested that you dont have more than .10" difference in OD because of the ABS.

 

Did you do actual measurements or are you just reading the chart? The chart does not have specs on the OEM tires. I have now physically measured five different 245's and all are essentially the same width as the OEM 225