I was wondering (and hoping this is an easy question to answer) if I went one series lower in tire profile if that's a real bad thing? Stock is 225/45r18 and I'd like to go with a 40-series. Any thoughts?

 

Staying within a 3% diameter change is desirable for the speedometer.
At the size you ask about, you'd be okay!

See here:

http://www.tirerack.com/tires/tirete...e.jsp?techid=7

 

Thanks man, I'll be keepin' that link for sure...

 

if you are getting new tires anyway get a 245/40 series tire. it fits and provides a touch more grip.

 

Will do, and thanks for the advice...I just ordered 2-225/40/18's. Gonna put those in the front and when the rears go, which is soon, will do the 245's...

 

Should've went with 245/40s all the way around.

 

Do you think if they're that different it'll affect performance much? I'll be honest, I know the basics about tires so any advice is welcome...

 

If you put the 225 up front and 245 in the rear, you will increase the understeer of the car. This is the unwillingness to turn in and the feeling of the car being pushed. If you put the 245 in front and 225 in rear you will increase oversteer. That is when the rear end looses grip first and the rear of the car starts to slide.

If you maintain the same width front and rear you will maintain the same balance as stock which is a good thing.

You should also try and keep the diameter the same front/rear and as close to stock as possible. If the diameters are different front to rear then the stability control will see the difference and kick in earlier than it should. With big differences in diameter the DSC will kick even during regular driving which would be really annoying.

Keeping the diameter close to stock will ensure the speedometer is correct. If you get a smaller diameter, the speedo will say you are going faster than you actually are, it will also put more miles on the car than you actually drove. A 3% change in diameter really wont be noticeable or affect anything too much.

My advice to you, since you already have the 225s on order, is to keep them and get the same size for the rear when the time comes.

 

All good stuff, very informative so thank you all very much for the feedback.

Juice, I am glad you said to stay as close to stock as possible. I got some new Motegi SP10's 18x8's last week after shopping for months for the cheapest, lightest, black, stock-sized wheel. Haven't seen any pics on here from anyone else with 'em on so I'll post as soon as my f*@#in' lugnuts get here. Not sure about forum rules on bashing but there is a guy on eBay...nevermind...

I did like some 17x8's, especially the Traklite 2.0's, but that was lookin' to be at least $1200 wherever I looked. That's too much for me right now so I was glad to stay stock and use the two good tires I had left.

Again, thanks all for the info and if there is anyone out there with some pics of either some Traklite's or SP10's, I'd still like to see 'em cuz mine aren't on yet!