Aspect ratio of tires...

[VoytekM5]

Nevermind... question answered below.

One of my favorite tires is the nitto invo. They are cheap and treat me well.

The guy at the tire store says that 315/35/20 is too tall for the car. My car is completely stock.

The tires are

275/35/20
315/35/20

Wheels are 9x10-11.

Can anyone confirm if these tires fit? I never did have the same height on staggered wheels before but hard to find tires in these sizes. Do you really need a smaller diameter in the rear?

[Fundguy1]

Do you know how aspect ratio works?
Stock is 265/35-20 front
295/30-20 rear.

[VoytekM5]

Originally Posted by Fundguy1

Do you know how aspect ratio works?

Apparently not because I thought 35s on both front and rear would be ok.

[Fundguy1]

Aspect ratio is the sidewall height as a % of tread width.
Stock have a sidewall of 295mm×0.30=88mm or about 3.5". Add 20 for the wheel and 7 for two sidewalls and they are about 27" diameter

315/35-20 sidewall is
315mm×0.35=110mm or about 4 3/8"

Add 20 for the wheel and 8-3/4" for two sidewalls and you're at 28-3/4" Not to mention 315 is pushing the limits width wise too.

[Fundguy1]

Fronts stock are 265/35-20.
They're 27.25" diameter. Front and rear diameter need to be almost equal or you mess up the computer.

[Fundguy1]

The calculation for overall diameter is

Tread Width x aspect ratio x 2 ÷ 25.4 + wheel diameter = overall diameter.

[VoytekM5]

Ahhh. Learn something new everyday. might have to settle for 305/30

Thanks man.

[Fundguy1]

So stock is
295 x 0.30 x 2 ÷ 25.4 + 20 = 26.96"

Yours is
315 x 0.35 x 2 ÷ 25.4 + 20 = 28.68"

See the problem?

[Fundguy1]

Heres a comparison of all the sizes with the calculations.
315 x 0.35 x 2 ÷ 25.4 + 20 = 28.68"
305 x 0.30 x 2 ÷ 25.4 + 20 = 27.2"
295 x 0.30 x 2 ÷ 25.4 + 20 = 26.97" OEM

275 x 0.35 x 2 ÷ 25.4 + 20 = 27.58"
265 x 0.35 x 2 ÷ 25.4 + 20 = 27.3" OEM

[VoytekM5]

Thanks man. I though the aspect was a measurement of the tire wall regardless of width.

[VoytekM5]

Do you know the proper offset that will get me to the fender on a 20x11 rim?

[Fundguy1]

I don't know f10 offsets yet. Still haven't landed one. I can help with e9x 335i though lol.

[GladiatorOwner]

Overall diameter needs to be within 2% (or real close to this) when comparing front to rear. If you keep it around 0 or 2% difference, it shouldn't throw off any nannies. Now offsets and widths, well, that's a whole different discussion.

Oh and I think the 2% or closer is more important on awd cars since the drive piece (power to the specific wheels on slipping and shit like that) is monitored by the car's system and reacts accordingly. Some of the smart guys can weigh in here for a better explanation but I think I'm directionally correct.

[achu]

Originally Posted by VoytekM5

Do you know the proper offset that will get me to the fender on a 20x11 rim?

11j et25

http://f10.m5post.com/forums/showthread.php?t=1345397