Tire Size Conversion

[Metalbeast]

Evening,

I am looking to order new wheels and wanted to see what everyone's thoughts on getting recommended tires for them are. My original wheels are P275/40R20 front / P315/35/R20 rear. What would I need to get to properly fit aggressively with new wheels that are 22x9 ET33 and 22x10.5 ET40? From what i'm being told 285/30 in front and 305/30 in back, as they don't make 315 in rear for the 22's. Any advice would be appreciated.

[Crazy1323]

So with AWD cars it is important to keep the diameter the same between the front and the back.

The first number is actually the tire width in mm. I'd look at the manufacturers specs and try to find sizes close in diameter. I think 285/30/22 and 305/30/22 would be too much of a difference in diameter. The fronts would always be spinning faster than the rears.

[Metalbeast]

Originally Posted by Crazy1323

So with AWD cars it is important to keep the diameter the same between the front and the back.

The first number is actually the tire width in mm. I'd look at the manufacturers specs and try to find sizes close in diameter. I think 285/30/22 and 305/30/22 would be too much of a difference in diameter. The fronts would always be spinning faster than the rears.

i mean that doesn't make much sense in seeing the stock sizes are not the same, hence the staggered. I think there is a certain percentage that is supposed to be tolerable between front and back. Either way I know it doesn't have to be the same all the way around so having diameter be the same doesn't make sense to me, unless you're referring to something else.

[PAX5]

Don't do it ... you'll forever regret it and kick yourself after the WOW factor has worn off ...

IMO.

[Metalbeast]

Originally Posted by PAX5

Don't do it ... you forever regret it and kick yourself after the WOW factor has worn off ...

IMO.

so don't order new wheels is what you're saying ?

[racermp]

Google miata tire size calculator. You can compare the 2 22's overlaying each other to see what the diff would be.

[PAX5]

Originally Posted by DJIntel

so don't order new wheels is what you're saying ?

Sure you can order new wheels. Just stay with wheel size 20" or less. You may even get another style wheel, just for variety, or ...

... spent your money on better tires and enjoy the ride.

[Metalbeast]

Originally Posted by PAX5

Sure you can order new wheels. Just stay with wheel size 20" or less. You may even get another style wheel, just for variety, or ...

... spent your money on better tires and enjoy the ride.

that's true, thanks

[Crazy1323]

Originally Posted by DJIntel

i mean that doesn't make much sense in seeing the stock sizes are not the same, hence the staggered. I think there is a certain percentage that is supposed to be tolerable between front and back. Either way I know it doesn't have to be the same all the way around so having diameter be the same doesn't make sense to me, unless you're referring to something else.

The stock 275/40/20 and 315/35/20 both have a diameter of 28.7". The widths are staggered but the diameter is the same.

A 305/30/22 has a diameter of 29.3" while a 285/30/22 tire has a diameter of 28.7". This difference causes the front wheels to always be turning faster and can cause wear on the center differential.

Will this break the car? I don't know, but the factory setup have the same diameter so the front and rear wheels turn the same speed to reduce unnecessary wear on the center differential.

If you would like 22's, a popular choice is 295/30/22 in the front and 335/25/22 in the rear. This give you a diameter in front of 28.8" and 29.1" in the rear. Not perfect but .3" difference is better than .6" difference. The only problem might be mounting a 335 tire on a 10.5" wheel.

[Metalbeast]

Originally Posted by Crazy1323

The stock 275/40/20 and 315/35/20 both have a diameter of 28.7". The widths are staggered but the diameter is the same.

A 305/30/22 has a diameter of 29.3" while a 285/30/22 tire has a diameter of 28.7". This difference causes the front wheels to always be turning faster and can cause wear on the center differential.

Will this break the car? I don't know, but the factory setup have the same diameter so the front and rear wheels turn the same speed to reduce unnecessary wear on the center differential.

ok thanks for explanation

[Crazy1323]

Originally Posted by DJIntel

ok thanks for explanation

No problem, I edited my post above.

Sorry for not answering your original question but my edit should give you a good idea. Pirelli makes an all season tire in the sizes I mentioned.

Good luck

[Metalbeast]

Originally Posted by Crazy1323

The stock 275/40/20 and 315/35/20 both have a diameter of 28.7". The widths are staggered but the diameter is the same.

A 305/30/22 has a diameter of 29.3" while a 285/30/22 tire has a diameter of 28.7". This difference causes the front wheels to always be turning faster and can cause wear on the center differential.

Will this break the car? I don't know, but the factory setup have the same diameter so the front and rear wheels turn the same speed to reduce unnecessary wear on the center differential.

If you would like 22's, a popular choice is 295/30/22 in the front and 335/25/22 in the rear. This give you a diameter in front of 28.8" and 29.1" in the rear. Not perfect but .3" difference is better than .6" difference. The only problem might be mounting a 335 tire on a 10.5" wheel.

Yes that is a perfect explanation, still getting ahold of these wheel things. I will probably stay with 20's but just wanted to comment on the difficulty of mounting the tire on the wheel. Would someone usually mount that big of a tire on an 11 or 12" wheel?

[Crazy1323]

Originally Posted by DJIntel

Yes that is a perfect explanation, still getting ahold of these wheel things. I will probably stay with 20's but just wanted to comment on the difficulty of mounting the tire on the wheel. Would someone usually mount that big of a tire on an 11 or 12" wheel?

11.5" is probably the minimum width a shop would be willing to put that tire on. 21" is a great choice because you can get Michelin Pilot Super Sports. I believe these to be the best warm weather tire out there. They are OE on X5M's with 21" wheels from the factory.

[Metalbeast]

Originally Posted by Crazy1323

11.5" is probably the minimum width a shop would be willing to put that tire on. 21" is a great choice because you can get Michelin Pilot Super Sports. I believe these to be the best warm weather tire out there. They are OE on X5M's with 21" wheels from the factory.

ok, I just didn't understand the ratio between wheel and tire width recommendation