autocross which tire and size??

md951 · md951's Garage

Here is my deal. I went to an autocross event put on by the cobra club. This was my first time with this car and this track. I did ok , but I thought I would be more competitive. almost every one there was running some kind of track tire. I ran fairly fast and also clean, but ran into turbo lag a few times. My car puts 340hp to the ground ,so I think I have enough power to be competitive.
My plan is to get a tires that will help. I currently run 18in wheels. I may stick with these rims or go back to a 16in rim and get tires for them. Has any one done alot of autocross with the 951 and were you competitive? what was your chose of track tires?

Please help!
thank you

ae1969 · 08-28-2006, 02:13 PM

Interesting.......... I will be hitting an SVT event in October.

JustinL has had the pleasure............ and he ended up being in the fast run group.

I am pretty sure he is running 245's all around. I am pretty sure he is running fusions. I run khumo's and I did not appreciate them until I had to run with my Proxes. Night and day.
I currently run 225F and 255rears. I need more grip in the front. So next year I am going to change my setup a little closer to Justins. Both tires are relatively cheap and a great bang for your buck.

If its a tight autocross you might have trouble if your turbo is really laggy (what are you running for a setup)? Those cobras make there power a lot quicker.
A longer road course and your 340rwhp will put the hurt on many of those cobras.

ae1969 · 08-28-2006, 02:14 PM

.....Find Justin in that pic

JustinL · 08-28-2006, 02:26 PM

I do ok on Falken Azenis tires if you're wanting a street/autox tire. I like running the same size tires all around too. Last year I had 245/45/16 fuzions, which were good, but this year I bumped up to 255/40/17 in the Azenis. I'm about 3% faster with the Falkens.

I've never run the course with an R-compound so I can't say how much would be gained over the azenis. From what I've heard, street tires will talk to you more and won't be as punishing for mistakes.

The first few times you run an autocross it will feel fast, but I can assure you that you will improve with more seat time.

JustinL · 08-28-2006, 02:29 PM

HEheh you were typing at the same time I was

Like Alex was saying, front grip is what makes my car faster than the mustanges not power.

md951 · md951's Garage

Thanx for the feedback.
After my first run the next 5 runs were all within 1/2 second. I know I need to push harder but some turns i just seem to push the front end. not sure where I need to improve,But turbo lag was a small issue. what size rims are you running?

JustinL · 08-29-2006, 06:29 AM

I use 17X9 for all 4.

nize · nize's Garage

assuming the weight stays the same, won't smaller wheels make you quicker in autocross ?

md951 · md951's Garage

That was my thought. but with the 18in wheels,I notice a big improvement on handling at least on the street. This is why I am not sure which way to go. The big wheels are about 16lb more than the 16in wheels. Plus the weight of the spacers.

JustinL · 08-31-2006, 06:25 AM

I'm of the smaller wheels, the better camp... but tire selection is a very big reason to go to bigger wheels. There just isn't anything really wide for 16" wheels.

nize · nize's Garage

goodyear eagle f1 gs-d3's available in 245/50 16's are pretty darn wide.

i haven't seen anything wider by any tire company for 16's other than hoosier, which are track-only tires.

nize · nize's Garage

Quote:

Originally posted by md951
That was my thought. but with the 18in wheels,I notice a big improvement on handling at least on the street. This is why I am not sure which way to go. The big wheels are about 16lb more than the 16in wheels. Plus the weight of the spacers.

handling on the street and autocross are different. the main advantage of smaller wheels is less rotational mass, which will give you quicker acceleration, which is very important in autocross. since (i'm assuming) you usually don't mash the gas down all the time on the street, you most likely wouldn't notice this difference.

bigger wheels would give you higher top speed (because they are taller), and possibly better cornering (because they are wider). the top speed probably won't be noticable in street driving, but the better cornering will.

it seems given identical cars with the only difference being wheel sizes, in autocross, the quicker-accelerating car with the smaller wheels will usually beat the better-cornering one with bigger wheels.

every competetive autocrosser i've ever met prefers smaller wheels with the widest, stickiest possible tires they can fit.

bleucamaro · 09-06-2006, 01:42 PM

My vote for autocross setup is a 16"x9" all the way around, or the smallest and lightest wheel that will clear your brakes. The reason is lower unsprung weight allows your suspension to do its job that much better. Hoosier and Kumho have some pretty decent auto-x tires out there, basically 2 groove slicks. Do some searching on tirerack.com and see what people think of the different tires. Also see which sizes have the lowest tire prices and greatest availability. 275/40-17 seems to be pretty popular. Also see what people recomend on more racing oriented forums, ie. corner-carvers etc.

jimbilly · 09-06-2006, 01:58 PM

You mentioned you're getting a lot of 'push', have you gotten a track/autox alignment? That will help as much as tires, and should minimize the push.
I'm running 245/45/16 Hoosiers on 16x8's all around, that works quite well. Slightly wider in the rear wouldn't hurt, but I like to be able to run a single size tire and wheel on front or rear. But 944's are really quite well balanced with same size tires all around.