Fitting Front tires for Autocross

bracer · 10-10-2017, 09:59 PM

Just putting this out there for posterity. For autocross I'd like to fit as large as front tires as possible. The issue is the two best tires out there are the RE-71R and the Rival S. They don't come in anything between 265 and 305 in 19". That stagger is too much, the car will push.

The best I've come up with is going with a 18" front (275/35/18) front and a 305/30/19 rear. It's still a big stagger. There is also a 285/30/18 but the diameter at 24.9" is a bit too small for daily driving, but ok for track / autocross only.

That led me to try seeing if a 305/30/19 RE-71R might fit. Unfortunately I think it's just a bit of a bridge too far. I tested out a 295/35/19 MPSS on a 19x10.5 wheel and tried moving the offsets around. The best I can figure is a 19x10.5 +19 is the best shot with a 10.5" rim, but I think we really need a 295/30/19.

19x10.5 ET34 with 10mm spacer. Not quite enough. Really need 15mm spacer or 19x10.5 ET19

Outside 19x10.5 34mm-10mm 295x35x19

Outsite 19x10.5 34-12.5295x35x19

Woodengun · 10-13-2017, 07:21 PM

Look at the apex wheel thread. I thought some were able to get 305 square to work with 3 or 3.5 negative camber up front.

bracer · 10-13-2017, 08:25 PM

They did using a Pirelli slick. These run really narrow, so a 305 is really about a 295 width, etc... Their 305 will actually fit a 10" rim pretty well.

MasterP · 10-14-2017, 08:38 AM

On competition tires the rim size makes a difference. For example a Michelin 30/65-18 is "300" mm unmounted. But on a 13" rim it's 334mm.

Not many tires in the "extreme" class come in a 295/30-19. The AD08R possibly.

I've run 285/30-18 RE71R on 18X10+27 with a 15mm spacer in front and no issues with my clearance to the strut.

Unless you have CCB's or don't like swapping wheels to autocross I don't see much merit for running 19's.

10-10-2017, 09:59 PM	#1
bracer Mr Bill 296 Rep 545 Posts Drives: GLC63 Join Date: Sep 2013 Location: Aliso Viejo iTrader: (1)	Fitting Front tires for Autocross Just putting this out there for posterity. For autocross I'd like to fit as large as front tires as possible. The issue is the two best tires out there are the RE-71R and the Rival S. They don't come in anything between 265 and 305 in 19". That stagger is too much, the car will push. The best I've come up with is going with a 18" front (275/35/18) front and a 305/30/19 rear. It's still a big stagger. There is also a 285/30/18 but the diameter at 24.9" is a bit too small for daily driving, but ok for track / autocross only. That led me to try seeing if a 305/30/19 RE-71R might fit. Unfortunately I think it's just a bit of a bridge too far. I tested out a 295/35/19 MPSS on a 19x10.5 wheel and tried moving the offsets around. The best I can figure is a 19x10.5 +19 is the best shot with a 10.5" rim, but I think we really need a 295/30/19. 19x10.5 ET34 with 10mm spacer. Not quite enough. Really need 15mm spacer or 19x10.5 ET19 Outside 19x10.5 34mm-10mm 295x35x19 Outsite 19x10.5 34-12.5295x35x19
	Appreciate 0 Tweet Quote

10-13-2017, 07:21 PM	#2
Woodengun Lieutenant 310 Rep 408 Posts Drives: Yugo Join Date: Apr 2015 Location: Norcal iTrader: (0)	Look at the apex wheel thread. I thought some were able to get 305 square to work with 3 or 3.5 negative camber up front.
	Appreciate 0 Quote

10-13-2017, 08:25 PM	#3
bracer Mr Bill 296 Rep 545 Posts Drives: GLC63 Join Date: Sep 2013 Location: Aliso Viejo iTrader: (1)	They did using a Pirelli slick. These run really narrow, so a 305 is really about a 295 width, etc... Their 305 will actually fit a 10" rim pretty well.
	Appreciate 0 Quote

10-14-2017, 08:38 AM	#4
MasterP Colonel 721 Rep 2,342 Posts Drives: All the M's Join Date: Aug 2012 Location: Where do you want me? iTrader: (8)	On competition tires the rim size makes a difference. For example a Michelin 30/65-18 is "300" mm unmounted. But on a 13" rim it's 334mm. Not many tires in the "extreme" class come in a 295/30-19. The AD08R possibly. I've run 285/30-18 RE71R on 18X10+27 with a 15mm spacer in front and no issues with my clearance to the strut. Unless you have CCB's or don't like swapping wheels to autocross I don't see much merit for running 19's.
	Appreciate 0 Quote