Hoping experienced autocrosser's can give me some insight on my friend's situation.


From email:

here i have a tire selection dilemma, it's driving me nuts ... what would be your
choice if you are given with the following points to think about ...

between a kumho v710 265/45-16 vs. hoosier a3s04 245/45-16

for the kumho on my car: it's heavier, little bit slower gearing, rub more and may
even need to cut the fender, plus i need to sell my volk to get a widest kosei k1
racing on 16in, 16x8.5 at 16.5 lbs, the final result is because it's wider at 11.2
in sect. width, unknown tread width, but i would imagine around 10.5in total tread
width!! and still retain the factory overall diameter and rpm, and less $

for the hoosier on my car: it's lighter, little faster gearing helps breaking and
accel. rub less, less mod on the fender, can retain my volk te37 @ 11 lbs, will need
extra spacers, tire is narrower compare to the kumho, also hoosier is fat at the
section width, 10.1 in section width and only 9.2" tread width and more $

what would you choose and why????? i need opinion and this decision is killing me
for the last couple of days...

 

If you could hold off until April you could have 245/45/16 V710s, that would seem like a good compromise.

 

If you have the power I'd say the 265. Don't be afraid to cut fenders if you're allowed to. I've been trying to convince some friends they need to for their Street Modified cars.

 

Have you posted this question on naisoc.com in their autocross/racing forum? There are probably a few on there that have run these set ups and can give you actual impressions from first hand experience.

From my experience with the RS, you want to watch that you don't go too short on the tire. The gearing is very short in these cars and you will run out of second gear real fast. In Kriemelmeyers STS RS we were running 215 45 16 Falken's and we were only getting about 47 mph out of second. So we had to use third quite a bit. I know it hurt us several times at nationals. On one of the nationals courses were were shifting between 2 nd and 3rd 6 times. Lots of time lost in the shifts.

I would lean toward getting as much tire under you as possible.

 

I would want to know if this is for SP or SM. How much power you are pushing makes a difference. It also makes a difference if you are dealing mostly with small local lots or bigger national style courses. Some people do very well in my region in STS 2.5's on our smaller, bumpy lots where the short gearing works for them. It's all horses for courses.

 

If the class he's running allows fenders to be cut, he shouldn't be getting any rubbing anyway. There's a guy running some truly bigass tires (they stick waaayyy out beyond the fenders) on a DSP 2.5RS (he also road races it in IT or something) with spring rates around 1000 lb/in. Post in the http://www.nasioc.com motorsports forum & you'll get the info you need (& usually more - LOL).

 

He's pushing roughly around stock horsepower ~170 hp, previously ran STS and now is going into DSP with a center differential biased towards the rear. He doesn't mind shifting multiple times during an autox run, so short gearing is ok for him.

 

Current theory says one of the reasons the DSP BMW's are so fast is the ability to fit big tires. That would suggest going with the wider ones and screw the gearing, up to a point. The E36 BMW's have a bit more torque and a fair bit more hp then the Subie, but are somewhat heavier so probably about the same torque to weight ratio. The serious ones are running the 265 or wider tires and stomping on other cars in the class, so I vote in the wider range at this point. Sure wish my GSR had the room/gearing the RS does so I could try the wider tires myself.