Tires/Wheels for AX vs. Track

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bigdork
Posts: 2
Joined: Sun Jun 29, 2008 11:03 am

Tires/Wheels for AX vs. Track

Post by bigdork » Mon Aug 25, 2008 2:04 pm

Hi Guys,
I promised myself that I would take my 993 out more this year and I'm off to a pathetic start - just managed to make the AX school and a "Performance Driving Clinic" down at Buttonwillow Raceway. Suffice it to say, I'm green but really beginning to enjoy getting my car out to run.

I noticed that there was a huge difference between the way my car ran at AX vs. on the track. I had to take my tire pressue way up for the track runs. I experimented with taking a bit of pressure off but the back end got really loose. I'm not sure if it is a function of my tires or the nature of the track vs. AX. I should also note that the car is completely stock with 17" wheels, 205/50 up front and 255/40 rear. The car is very comfortable on the street with this setup, however, I'm toying with the idea of getting some 18" wheels if I decide to track more.

So, was wondering if you guys have an opinion on wheel/tires for AX vs. Track? Would you invest in new wheels or am I just throwing money away?

Thanks
___________
Martin Chang
1995 993 C4

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psmith
Posts: 115
Joined: Fri Feb 23, 2007 3:31 pm

Re: Tires/Wheels for AX vs. Track

Post by psmith » Wed Oct 01, 2008 11:40 am

Hi Martin,

Just happened to run across this today, and though it's been awhile since you posted seems like you haven't had any responses, so:

I use the same wheels/tires for both AutoX and track events, but these are seperate from my street/rain set. And given the resources, I might consider different sets for Autocross and track. The key issues with each is largely performance. Having a seperate set of wheels for the track allows you to use a more aggressive tire than you would want on the street. While many people go this route, if you are just starting out, it will likely be easier to learn and get a sense for the limits of your car on street tires. As such, a second set of wheels could be nice, but not required. Further, as you learn more about driving and what you equipment will help you get faster, it's not uncommon to look back at such purchases and wish you had gone a different route (ie, 18" wheels will most likely be heavier than the 17"s, and the tires will be more expensive... 18"s have their plusses, but it's not always a given that this is what you will want for performance applications).

As for issues you had with pressure... I am suprised as I normally run lower pressues at the track than I would at an AX, since typically you will build up more heat (and thus pressure) at the track, where as AX runs hardly let the tires start to get warm. I would take a look at the pressures you are running and see if you can compare to others with the same tires. I don't drive a 993 myself, but from my experience I would think most street tires on one would be comfortable around 35 PSI Front, and 37 PSI Rear for normal driving. At and Autocross you would want that a little lower, and lower again for the track. If I recall, Porsche's suggested pressures have too much of a difference Front to Back, which might account for the problems you had.

Anyway, to sum up, play around some with your setup... another set of wheels is not a waste and will probably be something you'll want as you progress, but there's no need to rush for them until you begin to have a better handle on the car and your driving.

-Paul

Springgeyser
Posts: 121
Joined: Thu Feb 22, 2007 1:26 am
Location: San Mateo

Re: Tires/Wheels for AX vs. Track

Post by Springgeyser » Mon Oct 06, 2008 2:16 pm

Best investment is quality 'seat time' whether it is AX or DEs rather . Have instructor ride along with you to provide feedback and ask for ridealong to see how they are driving a course. Paul is a great instructor along with the rest of the PCA GGR AX guys.

I'll have a spare set of 18" lightweight 5 spoke with 225/265 that you can try to see how you like for the next Alemeda AX, just don't put cone marks on the rims.
Peter Lim

996 C4. AX6

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