Direwolf

I'm a total tire noob, and been spending the day educating myself trying to figure out what tires are compatible with the OE rims. I understand the rim width range is primarily what matters, currently Tire Rack has a great deal on the Kumho Ecsta SPT's 225/40ZR18 which I'm thinking about jumping on. But I just want to confirm with someone who knows before going ahead, are these tires compatible with the OE 18x8 rims?

HockeyRX-8

iTrader: (1)

yes but your speedo will be off by a couple of mph's....stick with 225/45/18 or get 245/40/18

Direwolf

So the 245/40's being wider cross section will create a taller sidewall closer to a true 45? Also, is it possible to get the speedometer recalibrated for the new size?

HockeyRX-8

iTrader: (1)

245/40 is very close to 225/45 so you wont need to recalibrate your speedo.Recalibrating the speedo can be done (only by the dealer IIRC), but it's better to stick with the 225/45 or 245/40

REDRX3RX8

I don't think the anyone knows how to change the speedo in the ECU, but I'm about to put 225/40r18 on 7.5 x 18 Enkei wheels.

For the speedo correction I use my scan guage corrected for the 3% slower actual speed.

225/40r18 is a very popular size which is run on 8x18 or 7.5 x18. It might fit your 8inch wide better than my 7.5 inch wide.

I have 225/45r18 kumho spt's on my 7.5 x 18 wheel now which looks perfect, but I've got Hankook ventus v12 k110 225/40r18 going on next. Some people and tests have said the hankook k110 has better grip dry or wet. They are about $14 more each at tire rack, but I get about 20k miles outta the spt's, and expect a little less from the hankoooks.

2tone

iTrader: (3)

you can get 'em if you want. it will, like they said, be a shorter sidewall which will:

make your wheel gap bigger, otherwise look better if you're lowered
stiffen the ride feel b/c less tire (rougher ride)
affect the speedo
affect odometer too

3% or whatever it is isn't that much, you can easily figure out what that is a cruising speed and adjust your driving. anyway, you can definitely get it, and i personally wouldn't worry about the speedo too much, but it is a different overall sidewall height so just think about if it's really worth it to save a few bucks.

Direwolf

The speedometer wouldn't be a big issue for me I don't think. At city speeds it's pretty insignificant.

I appreciate the help guys. I think I've got enough info now to make a good decision.

Mspeedpro

iTrader: (1)

I had 225/40/18s on my rx8 when I first got the car...

Speedo was off, ride wasn't very good but most importantly -- it just didn't look right at all.

I'd strongly suggest shelling out a few more dollars and getting 245/40/18s.

GeorgeH

iTrader: (2)

225/40s will give slightly better acceleration as they are shorter & lighter. That is one of the nice benefits of a shorter tire. It's not a huge difference, but it's enough to feel.

Probably slightly worse gas mileage on the freeway due to the higher revs.

But yes, they will look a little funy, and ride a little stiffer.

~Rev Free~

I am also thinking about picking this size up until I can afford some new wheels.. Car is completely stock, currently on stock size tires.

Does anyone have experience with this size tire on stock wheels under track condtions?

kersh4w

iTrader: (3)

i run 245/40s on my 18x8 rims. and i ran that size on my stock rims too.