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[hl0m4n]

what is the best rear tire size matched with 255/35 front and not running any spacers on zcp rims?

is it alright to mix aspect ratios? any benefits/disadvantage of mixing and is it safe?

help much appreciated, thanks guys .

oem zcp:
F: 245/35 9x19 et31
R: 265/35 10x19 et25

rear sizes available:
275/35
285/30
295/30

[///M Rakete]

Originally Posted by hl0m4n

what is the best rear tire size matched with 255/35 front on zcp rims? i want to be closest to oem feel and maintain oem parameters. i will not be using spacers as well.

could someone also explain any benefits/disadvantages of mixing aspect ratios?

help much appreciated, thanks guys .

rear options available:
275/35, 275/30, 285/30, 295/30

oem:
F: 245/35
R: 265/35

285/30 would replicate the setup as found on the M3 GTS.

[ben@tirerack]

Aspect ratio is just a number, it is the tire height that matters.

The M3 is not ultra-sensitive to changes in tire height. As long as the overall diameter of the rear tire is at least as tall as the front, you should have no trouble. The factory setup, with wider rears of the same aspect ratio, gives you a rear tire that is about 1/2" taller.

[hl0m4n]

hey ben, so which setup is best?

255/35 & 275/35
255/35 & 285/30
255/35 & 295/30

[LarThaL]

Originally Posted by hl0m4n

hey ben, so which setup is best?

255/35 & 275/35
255/35 & 285/30
255/35 & 295/30

Simple math:

255 x .35 vs 275 x .35 vs 285 x .30 vs 295 x.30

285/30 gives you an equal tire diameter/sidewall height to 245/35

255/35 and 295/30 have equal overall tire diameter/sidewall height.

255/35 and 275/35 have tire sidewalls that are 3.5mm taller than the stock 245/265 tires.

See.....it's all simple math.

[ben@tirerack]

Originally Posted by hl0m4n

hey ben, so which setup is best?

255/35 & 275/35
255/35 & 285/30
255/35 & 295/30

There is no 'best' per se. Wheel fitment and tire availability will usually help make your choice for you. 255 front 275 rear will most closely replicate the proportion of front to rear found in the stock tires. But as noted above 285/30R19 Rear has been used successfully by BMW, and 295/30R19 rear gives a very exact match of the front height to the rear.

If you post your wheel sizes and offsets, you will likely get more specific opinions and advice.

[Malek@MRF]

285-30-19 would be the best. No question about it.

We have done this and it not only looks the best, it makes the car feel great too.

[M3SQRD]

Originally Posted by Malekreza11

285-30-19 would be the best. No question about it.

We have done this and it not only looks the best, it makes the car feel great too.

+1 Come spring I plan on switching to a 285/30 on the ZCP rears. I'm hoping by then Michelin will have released the PSS in this size.

[hl0m4n]

280/30 seems best. when i looked at various pictures of 295/30 it looks like the tire is eating up the rim and looks really stretched. i know the 10 can fit the 295 but it just looks odd.

so now im stuck with 275/35 & 280/30. im selecting an all season tire and michelin pilot a/s has the 280/30 while the new bridgestone pole position 70 max is 275/35.

the michelin pilot a/s has been around for awhile now while the bridgestone just came out recently and has pretty good reviews over the michelin.

will the 255/35 & 275/35 also be good and keep oem parameters?

im hoping bridgestone comes with the 285/30 in a few months but most likely not...

[Daft]

When going to a different tire you want to stay as close as you can to the diameter of the stock size. Use this little calculator to help out: http://www.miata.net/garage/tirecalc.html (requires Java installed)

[Dave07997S]

Originally Posted by Malekreza11

285-30-19 would be the best. No question about it.

We have done this and it not only looks the best, it makes the car feel great too.

You came around huh... I always liked the 285/30 setup..

[Henri_K]

I have the same question. Just got some MORR wheels 9" fronts and 10" rears and wondering what tire size to get. I'm on stock suspension but from my understanding 255/35 and 275/35 will lift the car up a little since these tires will have a taller sidewall then stock 245/35 and 265/35.
As much as I would like a wider tire I'm affraid that 245/35 and 265/35 will be the best solution.

Whoever is saying that 285/30 is perfect I think they are wrong. The new tire diameter will be 2.17% smaller then stock 265/35 leading to a wrong speedometer read out. 305/30 would be a perfect match to 265/35. But they won't fit on a 10" wide rear wheel.

Any input is welcomed.

[M3SQRD]

Originally Posted by Henri_K

Whoever is saying that 285/30 is perfect I think they are wrong. The new tire diameter will be 2.17% smaller then stock 265/35 leading to a wrong speedometer read out. 305/30 would be a perfect match to 265/35. But they won't fit on a 10" wide rear wheel.

A 2% error is in the "noise" considering the e9x M3 speedometer is already off by 5-10%!

[Dave07997S]

Originally Posted by Henri_K

I have the same question. Just got some MORR wheels 9" fronts and 10" rears and wondering what tire size to get. I'm on stock suspension but from my understanding 255/35 and 275/35 will lift the car up a little since these tires will have a taller sidewall then stock 245/35 and 265/35.
As much as I would like a wider tire I'm affraid that 245/35 and 265/35 will be the best solution.

Whoever is saying that 285/30 is perfect I think they are wrong. The new tire diameter will be 2.17% smaller then stock 265/35 leading to a wrong speedometer read out. 305/30 would be a perfect match to 265/35. But they won't fit on a 10" wide rear wheel.

Any input is welcomed.

Well being the fact the GTS comes with 285/30s out back and I have been running this tire now for almost 18mos. I am very happy with this setup.

Dave

[KennyPowers]

Originally Posted by Dave07997S

Well being the fact the GTS comes with 285/30s out back and I have been running this tire now for almost 18mos. I am very happy with this setup.

Dave

Can you tell a ride comfort difference?

I was considering 285/35 bc the 285/30 sidewall is a good bit shorter than the oem 265/35 much less 275/35.

Thanks for your feedback.

[Dave07997S]

Originally Posted by KennyPowers

Can you tell a ride comfort difference?

I was considering 285/35 bc the 285/30 sidewall is a good bit shorter than the oem 265/35 much less 275/35.

Thanks for your feedback.

Negligible...the car feels great.

A 285/35/19 is just to tall..looks like a tire that belongs on a sport SUV.

Dave

[KennyPowers]

Originally Posted by Dave07997S

Negligible...the car feels great.

A 285/35/19 is just to tall..looks like a tire that belongs on a sport SUV.

Dave

Good feedback, thanks.

We will have to agree to disagree on the tire size aesthetics. I prefer a healthy sidewall rather than an overly thin sidewall. Glad to hear the car feels good though, I will definitely consider 285/30 going forward.

I'd be curious to hear from anyone runnig 255/35 and 285/35.

[OC3]

One source of reference...

.

[Henri_K]

So 275/35/19 would be the best scenario?
OD is only 7 mm bigger.

[///M Rakete]

Originally Posted by OC3

One source of reference...

.

The math from these calculators is interesting but nothing more. Each tire has a "spec'ed" size and a real size. The spec size is for general information/fitment only. It's the real size that ultimately counts.

Pirelli P Zero Corsa diameters...

Front: 255/35-ZR19 measures at 25.94" OD
Rear: 285/30-ZR19 measures at 25.88" OD

Unloaded but inflated and mounted. The true rolling circumference would be fractionally less than Pi times the OD due to the tire flattening against the road surface when loaded.

The difference in outer diameters is only 0.23% or nothing.