255s on 8.5" Rims for racing?

z_man93 · 05-17-2011, 05:33 PM

I'm trying to come up with a track setup that is decent and affordable. I have qty6 M68 wheels already, so it's a sensible choice to go with considering the 8.5" wheels are only around 21lbs. I've only done 6 autocrosses over the past year, so I don't need anything extremely competitive. I'd rather spend my money on more seat time. I am however driving at the limits of my current setup.

I'd like to go with a square setup all-around with my M68 8.5" and wide-as-sensible Star Specs. I'm trying to do as many AutoXs as possible and also fit in a couple NASA HPDEs this summer. For SCCA STX the widest tire I can go with is a 265. I couldn't imagine fitting a 265 on an 8.5" wheel so I'm leaning towards a 255.

My question is whether or not a 255/40/R17 is too wide for an 8.5" wheel for competition driving? That's ~.75" overhang on either side.

BartenderPlease · 05-17-2011, 05:51 PM

That size will work fine. I used and abused a 255/40/17 on my rear m68's. They were BFG, which ran much noticeably fatter than OEM 335i sport tires (255/35/18).

Do it

LivesNearCostco · 05-17-2011, 08:38 PM

That is what I did for AutoX--255/40/17 Hankook R-S3 on 8.5" rims. They don't look too wide, but I haven't driven them in any events yet so can't say. I'm signed up for the BMW CCA AutoX this Saturday at Qualcomm, so maybe my new tires and I will see you there? (I don't do SCCA yet.)

I've seen this question come up a few times in the track, AutoX and club racing forum on bf.c. Half the respondents say what BartenderPlease did--Do It! The other half say 255 width tires feel more precise and grip better on a 9" rim and you should not run more than 245 width tires on an 8.5" rim.

2003 325i · 05-18-2011, 01:50 AM

255 is an OEM installed width tire on most BMW 8.5" wide rims. I don't see how/why it'd be a problem. 255/35 R18s came on the rear of the style 293s I bought from a Z4 owner, 8.5" wide.

woorick · 05-18-2011, 03:35 AM

Quote:

Originally Posted by 2003 325i

255 is an OEM installed width tire on most BMW 8.5" wide rims. I don't see how/why it'd be a problem. 255/35 R18s came on the rear of the style 293s I bought from a Z4 owner, 8.5" wide.

My impression on factory sized tires is that usually performance cars will have a staggered setup vs. a square setup because it would make over steering less likely. On a staggered setup.

Sent from my DROID2 using Bimmer App

VMRWheels · 05-18-2011, 02:00 PM

Quote:

Originally Posted by woorick

My impression on factory sized tires is that usually performance cars will have a staggered setup vs. a square setup because it would make over steering less likely. On a staggered setup.

Sent from my DROID2 using Bimmer App

It's somewhat cosmetic as well.

Some people like seeing the rear wheels a bit more aggressive than the fronts, but for every day driving I'd say staggered is a bit safer.

05-17-2011, 05:33 PM	#1
z_man93 Registered User Join Date: Oct 2009 Location: San Diego Posts: 27 My Ride: 328ci View My Garage	255s on 8.5" Rims for racing? I'm trying to come up with a track setup that is decent and affordable. I have qty6 M68 wheels already, so it's a sensible choice to go with considering the 8.5" wheels are only around 21lbs. I've only done 6 autocrosses over the past year, so I don't need anything extremely competitive. I'd rather spend my money on more seat time. I am however driving at the limits of my current setup. I'd like to go with a square setup all-around with my M68 8.5" and wide-as-sensible Star Specs. I'm trying to do as many AutoXs as possible and also fit in a couple NASA HPDEs this summer. For SCCA STX the widest tire I can go with is a 265. I couldn't imagine fitting a 265 on an 8.5" wheel so I'm leaning towards a 255. My question is whether or not a 255/40/R17 is too wide for an 8.5" wheel for competition driving? That's ~.75" overhang on either side. __________________ Anthony Colin Bruce Chapman: Adding power makes you faster on the straights. Subtracting weight makes you faster everywhere.

05-17-2011, 05:51 PM	#2
BartenderPlease Registered User Join Date: Sep 2006 Location: Charleston Posts: 8,801 My Ride: 328i Sport View My Garage	That size will work fine. I used and abused a 255/40/17 on my rear m68's. They were BFG, which ran much noticeably fatter than OEM 335i sport tires (255/35/18). Do it __________________ Gottalovethexi: thx for the old p-chopped sig \| BBS CH \| FK coils \| RE Bushings/Mounts \| K&N Intake \| ZHP box/no resonators \| \| 330i brakes \| FX-R + Orion V4 \| Full Exterior LED kit \| JL Audio in trunk \|

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05-17-2011, 08:38 PM	#3
LivesNearCostco Registered User Join Date: Jan 2010 Location: Silicon Valley Posts: 753 My Ride: 2003 ZHP 6MT View My Garage	That is what I did for AutoX--255/40/17 Hankook R-S3 on 8.5" rims. They don't look too wide, but I haven't driven them in any events yet so can't say. I'm signed up for the BMW CCA AutoX this Saturday at Qualcomm, so maybe my new tires and I will see you there? (I don't do SCCA yet.) I've seen this question come up a few times in the track, AutoX and club racing forum on bf.c. Half the respondents say what BartenderPlease did--Do It! The other half say 255 width tires feel more precise and grip better on a 9" rim and you should not run more than 245 width tires on an 8.5" rim.

05-18-2011, 01:50 AM	#4
2003 325i Registered User Join Date: Mar 2009 Location: New Hamburg, Ontario, Canada Posts: 1,456 My Ride: '03 Orient Blue 325i View My Garage	255 is an OEM installed width tire on most BMW 8.5" wide rims. I don't see how/why it'd be a problem. 255/35 R18s came on the rear of the style 293s I bought from a Z4 owner, 8.5" wide.