My plan was to go 275/40/17 on my 9.5 rear rim. My fronts will be 225/45/17 on 8in. But im leaning to a tire that only comes in 255's and smaller. So do I still get the 255/40? or do I go 45 now? Im still unclear on why we put a 40 series in back and a 45 in front anyway? Sorry if I dont make total sense I have a 3 yr old on my back and hes CHOKING me!

Its all good my 3 year old just got done choking me out! For the rear here is what I would do...

If you go 255's in the rear.....

255/45/17......26.0 tall....rear
225/50/17......25.9 tall....front


Now if you go 275's in the rear....

275/40/17.......25.7 tall...rear
235/45/17.......25.3 tall....front

If you go 255's in the rear.....

255/45/17......26.0 tall....rear
225/50/17......25.9 tall....front


Now if you go 275's in the rear....

275/40/17.......25.7 tall...rear
235/45/17.......25.3 tall....front

These sizes have proven to work - especially if the backspace is correct. Notice as the tire gets wider it also gets taller. The reason you would use a higher profile in the front (45 as opposed to 40 in the rear) is to keep overall tire height near the same. If you use the same series front and rear since the rears are wider they will be about an 1" taller. If you want a raked look (down in the front) fine but most of us want these cars to sit near level especially if your leaning to the "pro-touring" look. Hope this helps.

My plan was to go 275/40/17 on my 9.5 rear rim. My fronts will be 225/45/17 on 8in. But im leaning to a tire that only comes in 255's and smaller. So do I still get the 255/40? or do I go 45 now? Im still unclear on why we put a 40 series in back and a 45 in front anyway? Sorry if I dont make total sense I have a 3 yr old on my back and hes CHOKING me!

I would go 255/45 for the rear and still use 225/45 for the front especially, if you've lowered your car. The 45 in the rear will fill a little space, and the 45 up front keeps it reasonable for height (I believe it'd be 25.4"). In my case (with front dropped 1" and rear 1.5"), I'm running 235/45 front & 255/45 rear. Here are pics of these very sizes:

http://img.photobucket.com/albums/v509/dbx/Thksgvg002.jpg
http://img.photobucket.com/albums/v509/dbx/CarPic003.jpg

As you can see, the car sits level (despite on pic taken on a slant). But keep in mind; I dropped the front 1" and the rear 1.5".....and then 235/45 sits 25.4", which is a 1/2" lower than the rear 255/45 @ 26.1".

Great it makes sense now, kinda. Will I be level if I run a 225/45 front and a 255/45 rear?

Great it makes sense now, kinda. Will I be level if I run a 225/45 front and a 255/45 rear?

I guess I didn't make enough sense :D Whether or not you'd be level would be anyone's guess. Again, it'll depend on your car's current suspension to start with. And even then, each car can be quite different.

The best I can tell you from here, is to measure the current "rake" you have (body to ground measurements from front & back). Then find the diameter of your current wheel/tire size (in inches). Let's say you currently have a 30" high tire in the rear...and that your cars sits 1" higher in the back than it does in the front. If you change to a 28" high tire, you'll effectively lower the back 1" (half the 2" difference between 30" & 28") and have the car sit more level. I hope someone comes along with a more simple way to explain this, as I'm sure my example is probably screwed up :D.

You explained everything very simple and easy to understand. I have coilovers in front so im not to worried about the rake.Im more concerned of the front tire wall being bigger than the rear tire wall.

Stick with the sizes I listed and the sidewall weight will look the same front and back.

Went to Costco today and got a cool BFG book with all the sizes height and width, including diameter of the tire on different rim sizes. Gunna order some tomorrow.

Went to Costco today and got a cool BFG book with all the sizes height and width, including diameter of the tire on different rim sizes. Gunna order some tomorrow.

You might find this site even easier: http://www.wheelsmaster.com/rt_specs.jsp

Standing back from your car, the difference between a 40 & 45 profile can be hard to tell. Or at least, it doesn't stand out. Get whatever combo you want, but keep in mind that you're desired results may dictate tire sizes that are NOT identical in height. And again, your current suspension will be a huge factor.