wannabetoughguy

I ordered 17x9 +40 that will be here shortly and I need to choose tires. I have a G37X sedan lowered on megan racing springs.

Would 255/50/17 be too wide or is 245/50/17 ideal? Also, is 50mm sidewall (5mm less than stock) a good idea or is it possible to go lower on a 17? I wouldn't mind running 255mm wide tire if it won't hurt performance. Thanks in advance.

projectpanda13

iTrader: (2)

you can run either tire widths just fine on your 9.0" wheel. the second number is called the aspect ratio and is your sidewall as a percentage of the tire section's width

255mm width X 50% = 127.5mm sidewall height from rim to tread edge.

245mm X 50% = 122.5mm

so a 255/50R17 has a diameter of 27 inches. and a 245/50R17 has a diameter of 26.6 inches. Both of these will be fine as they are close tot he stock diameter (225/55R17 = 26.7 inches)

you can run a smaller diameter if you wanted, but it'll make your speedometer read incorrectly.

I'm personally running a 26 inch diameter setup on my cat and my speedo is about 4mph off.

stealthee

50 is not the sidewall height in mm, 50 is a percentage of the width.

wannabetoughguy

Thanks. Any input on choosing 245mm or 255mm wide tires? Will 255s fit properly?

JSolo

iTrader: (14)

What's the rationale for going with a 17" wheel vs 18"/19"?

wannabetoughguy

I prefer the way 17s look.

projectpanda13

iTrader: (2)

use this chart as a general guide. 255 is fine on a 9.0" wheel

stealthee

To be honest 235 is too narrow for a 9" wheel. I had 245's and they were already looking stretched. I'm actually running 275's on the 9" wheels now mainly because of my widebody fenders.

projectpanda13

iTrader: (2)

it depends on the specific tire size. a 235/50R17 is a 26.3" diameter but by TRA and ETRTO standard, has a maximum approved wheel width of 8.5"
A smaller 235/45R17 is a 25.3" diameter but has a maximum approved wheel width of 9.0"

The charts found on online are just very, very general guides. Discount Tires and other larger chain stores will tell you if a tire is not approved to be fitted on a certain wheel width. Its liabilty on their end.