Gurp925

Hey guys just picked up some 10" , 8.5" Vossen CVT, after mounting with my tires 275's in the rear and 245 in the front I've noticed the rear tires stretch way more then the squared look in the fronts with the smaller rim. what do you guys think about a 275,235 set up? would I see any problem doing this?


Thanks ahead of time!, oh and for reference its a 08 coupe

blnewt

iTrader: (13)

No, just make sure the series on the fronts is one group higher, so if you have a 275/35 rear, make sure the 235 is a 40 series, not a 35.

Gurp925

Oh sweet why does the sidewall have to be bigger in the front then the rear?

stealthee

Its not bigger. The way it works is the first number is the width in millimeters. The second number is the percentage of the width. The way to calculate the tire overall diameter is this

(This is copied and pasted from a post I made on another forum)

Stock tire size on my 07 GT is 225/55/17

225 is the section width in millimeters. To convert that to inches you would divide it by 25.4.
55 is percentage of diameter that is the sidewall height.
17 is, obviously, the rim diameter

The math formula to figure out the overall diameter would be the following:

((225/25.4) * .55) * 2) + 17 = 26.744

If I decided I wanted a little bit wider and 18" I would go with 245/45/18

((245/25.4) * .45) * 2) + 18 = 26.681

Gurp925

Thanks for the reply but still doesn't answer my question as to why the "series" has to be higher. And say i had a 245/55/17 vs a 245/45/17 would that 245/45/17 have a smaller sidewall just based on the math?

stealthee

Yes. 245/45 would be smaller than a 245/55. 55% of 245 is 134.75mm (5.31") 45% of 245 is 110.25mm (4.34")

245/45/17 is 25.7"
245/55/17 is 27.6"

The reason the series has to be higher is because of the width being different. If you were running a staggered set up but wanted overall diameter to be the same you need to do this.

For instance if you wanted to run 245/40/18 in the rear and a narrower tire in the front, but wanted to stay the same in diameter you could run 215/45/18 in the front.

The 245/40/18 are 25.62" overall diameter
The 215/45/18 are 25.72" overall diameter

As the width goes down then the percentage of the width (the second number) needs to go up.

blnewt

iTrader: (13)

Just mess around with this calculator, try various combos and you'll see how the diameter changes as you go wider while keeping the same series throughout your choices.
And for AWD you need to keep your front to back diameters under 1%. For RWD you have more wiggle room, under 3% is the general consensus to avoid issues w/ your Traction control and ABS systems, but a bit of a gray area TBH.

https://www.myg37.com/forums/tire_rim_calculator.php

slartibartfast

iTrader: (7)

The goal is to retain the stock wheel/tire diameter. That's the purpose of the above machinations. The car is programmed with wheel diameters so you have to be careful how you juggle wheel/tire sizes. Especially if you're AWD.

blnewt

iTrader: (13)

Yep^^^
Here's a list of the most common combos that WILL work w/ AWD, and notice the series of the tire changes throughout.
https://www.myg37.com/forums/brakes-...ml#post3992771

slartibartfast

iTrader: (7)

I should say the ECU is programmed with the OE tire diameter. You can change wheels and tires to your heart's content as long you stay close to that original diameter.