TIRE SIZES AND DIAMETER.....

[1DumpedViper]

i HAVE SPENT HALF MY DAY TRYING TO FIGURE THIS OUT. Everyone knows the Pirelli's are out of stock on the 345/25/20's for the next two months. Looking at tireracks measurements something dawned on me. They use a 12" width wheel and Pirelli uses an 11.5" width wheel to show their measurements. SOmeone look below and tell me if my math is right. I want tires for my new rims and dont know what to do.

Per tire rack-
Stock runflats- 345/30/19 is 27.4" diameter using a 12" wide wheel. Does that mean the diameter is actually 26.4" on a 13" wheel?

Michelin Ps2 in 335/30/20 shows a 28" diameter on a 12" wide wheel, which is actually 27" in the 13" width wheel?

Pirelli 345/25/20 shows 26.8" diameter on an 11.5" wheel, which is 25.3" diameter on a 13" wheel?

If my math is correct, the PS2 tire is only .6" taller than stock, where as the Pirelli is 1.1" shorter than stock. If this is the case, wouldnt it be better to put on the michelin since the computer would have less trouble with the tire being .6 taller rather than a whopping 1.1" shorter? Someone set me staright because I'm loosing my mind!

 

[Viper X]

Hey Mike,

Don't worry about the computer. I regularly change wheel / tire sizes / heights. No impact except on the speedo and it's minor.

You will have to deal with the tire pressure sensors in each wheel.

The SRT-10s are geared a bit tall with the stock tires. I would and do run the shorter tires if possible. You will feel the difference with a taller tire and stock gears.

Your math is OK but this isn't exactly how the tires measure in reality on the various rim. The sidewalls do flex and allow for the differing rim widths without getting signigicantly shorter or taller.

See you at Crystal Cove.

Dan

 

[Chuck 98 RT/10]

The width of the wheel is irrelevant.

The 20-inch Pirelli has as shorter sidewall which is why the overall diameter is smaller.

Pirelli
2(345mm x .25)=172.5mm / 25.4 = 6.79" + 20" = 26.8"

Michelin PS2
2(335mm x .30)=201mm / 25.4 = 7.91" + 20" = 27.9"

 

[Racer Robbie]

Z06vette, Michelin also makes tires in the stock oem size that are not run flats. They breally work well on the street. They are a lot sticker, smoother riding, and quiter.

Robbie

MICHELIN 275/35ZR-18 PILOT SPORT TIRES, FRONT
MICHELIN 345/30ZR-19 PILOT SPORT TIRES, REAR