Autocross wheels and tires
06-04-2001, 12:18 PM
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Autocross wheels and tires
I just got back from a SUPERBLY run Zone 7 autocross event at Mather Field this weekend near Sacramento and now I want more out of
my car. So, the obvious first step is losing the street tires in favor of something stickier...
I have a gray-market '86 911 Cab which puts me in PCA L-Production class because of the higher compression ratio European engine. So, I think I can go to full on racing tires in Production class, no? I don't need to stick to the DOT approved streetable tires, in other words. Is this advisable? I have no experience with real race tires, so I don't know how they compare in life-span, grip, shelf-life, etc. to street-legal autocross specific tires like Khumos and R1s. I have a lot of experience with those types of tires from years ago in SCCA autocrossing. I wouldn't even know where to buy racing slicks! Any advice in this area is much appreciated.
Second, what to do about rims... I run Fikse 8 and 9x17's for the street, but I imagine I want smaller (diameter at least) wheels for autocrossing. I have a set of 6 and 7x16 Fuchs. I was thinking of running the 7s in front and getting a pair of 8x16s for the back. What do you think of that combo What size race tires would I put on those rims? Any other advice for wheels?
Thanks in advance for any advice, and thanks to those who helped in any way with the events this past weekend.
Cheers,
Dean
my car. So, the obvious first step is losing the street tires in favor of something stickier...
I have a gray-market '86 911 Cab which puts me in PCA L-Production class because of the higher compression ratio European engine. So, I think I can go to full on racing tires in Production class, no? I don't need to stick to the DOT approved streetable tires, in other words. Is this advisable? I have no experience with real race tires, so I don't know how they compare in life-span, grip, shelf-life, etc. to street-legal autocross specific tires like Khumos and R1s. I have a lot of experience with those types of tires from years ago in SCCA autocrossing. I wouldn't even know where to buy racing slicks! Any advice in this area is much appreciated.
Second, what to do about rims... I run Fikse 8 and 9x17's for the street, but I imagine I want smaller (diameter at least) wheels for autocrossing. I have a set of 6 and 7x16 Fuchs. I was thinking of running the 7s in front and getting a pair of 8x16s for the back. What do you think of that combo What size race tires would I put on those rims? Any other advice for wheels?
Thanks in advance for any advice, and thanks to those who helped in any way with the events this past weekend.
Cheers,
Dean
06-04-2001, 01:30 PM
#2
Dean,
I was at Mather on Sunday. Good day, not too hot.
Based on the description I am guessing you had the white cab with roll bar? I had (one of the several) 86 red cabs.
A couple thoughts on trade offs.
If you are going to get racing wheels, why not go for 15 inch. You can get more gear ratio improvement and lowering. I have 15 inch cookies for the track, and 17 inch for the street.
The full on race slicks are less flexible. You can't (legally) drive them on the street. Even if you change them at the track, do you drive out to get lunch/fuel/hotel? They will also have less puncture protection. These really only makes sense if you trailer in and have another vehicle.
They will offer a little more stick. Don't know about that class rule.
I was at Mather on Sunday. Good day, not too hot.
Based on the description I am guessing you had the white cab with roll bar? I had (one of the several) 86 red cabs.
A couple thoughts on trade offs.
If you are going to get racing wheels, why not go for 15 inch. You can get more gear ratio improvement and lowering. I have 15 inch cookies for the track, and 17 inch for the street.
The full on race slicks are less flexible. You can't (legally) drive them on the street. Even if you change them at the track, do you drive out to get lunch/fuel/hotel? They will also have less puncture protection. These really only makes sense if you trailer in and have another vehicle.
They will offer a little more stick. Don't know about that class rule.
06-04-2001, 09:50 PM
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Hi Dean, Clark,
I was at the Autocross too.
I hear the hot ticket is fuchs 15 7 & 8 with 225/50 Kuhmos victor racers or Hoosier (Hoosiers are stickier=faster=faster wear). Look at Glenn Brooksby's cab. He has Kuhmos with 7 & 8 Fuchs 225/50 front and rear. He also has a limited slip....
The Dot -R tires put you into the improved class. I was running 205/55 -16 and 245/45 -16 Yokos on Fuchs in the L class.
I have Fuchs 15" 7 & 8 and will be getting some Kuhmos on these, this will put me in the Li class (with Glenn, ouch).
Check out GGR PCA for more Auto-cross rules and classes. www.pca-ggr.org
Nick H.
'85 Carrera
Fuchs 7 & 9
I was at the Autocross too.
I hear the hot ticket is fuchs 15 7 & 8 with 225/50 Kuhmos victor racers or Hoosier (Hoosiers are stickier=faster=faster wear). Look at Glenn Brooksby's cab. He has Kuhmos with 7 & 8 Fuchs 225/50 front and rear. He also has a limited slip....
The Dot -R tires put you into the improved class. I was running 205/55 -16 and 245/45 -16 Yokos on Fuchs in the L class.
I have Fuchs 15" 7 & 8 and will be getting some Kuhmos on these, this will put me in the Li class (with Glenn, ouch).
Check out GGR PCA for more Auto-cross rules and classes. www.pca-ggr.org
Nick H.
'85 Carrera
Fuchs 7 & 9
06-06-2001, 12:04 PM
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Thanks for the info and advice, guys. Yes, Chuck, that was me in the white cab with the rollbar. Perhaps you saw me spinning in circles on the course? 
The 15's make sense to me. And, as Steve Silver(drives that badass #76 C4) has pointed out to me, slicks are only allowed on Modified class cars in GGR region (others?)
So, I am now looking for a set of 7 and 8 15's and will make the price/wear/fun decision on Hoosiers versus Kumhos once I see what I have to spend on wheels.
You guys going to Reno in a couple weeks?
Thanks again,
Dean
The 15's make sense to me. And, as Steve Silver(drives that badass #76 C4) has pointed out to me, slicks are only allowed on Modified class cars in GGR region (others?)
So, I am now looking for a set of 7 and 8 15's and will make the price/wear/fun decision on Hoosiers versus Kumhos once I see what I have to spend on wheels.
You guys going to Reno in a couple weeks?
Thanks again,
Dean
06-07-2001, 05:45 AM
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Dean,
I won a number of trophies in the late 80s with my 82 911 SC Targa even though I am not a very skillful driver.
My SC was originally equipped with 16” wheels having 6” & 7” width. I upgraded
to Fuchs turbo wheels having 7” & 8” width. Keeping the stock size 205 & 225 mm width tires I noticed a BIG difference in stiffness (over bumps and cornering). I was amazed that by increasing the wheel width with the stock tire size handling was greatly improved!!! In contrast, my competitors ran 6” & 7” wheels with wider tires. I am sure they had LOWER grip with the wider tires.
My second advantage was I ran on Yokohama A008Rs while my competitors ran on BF Goodrich tires. I suspect the solid rubber shoulder of the Yokes gave me an advantage over the BFGs which had stylish grooves.
The nest issue is tire diameter. Yes, you can reduce tire diameter with smaller diameter wheels BUT can you get the highest performance tires in 15” diameter?
With stick diameter tires I could run up to 40 MPH in first gear. For most
autocrosses I would run completely in 1st gear. Smaller dia tires would give faster acceleration but I would lose time shifting back and forth from 1st to 2nd gear throughout the course.
Regards,
George
In sunny Arizona
I won a number of trophies in the late 80s with my 82 911 SC Targa even though I am not a very skillful driver.
My SC was originally equipped with 16” wheels having 6” & 7” width. I upgraded
to Fuchs turbo wheels having 7” & 8” width. Keeping the stock size 205 & 225 mm width tires I noticed a BIG difference in stiffness (over bumps and cornering). I was amazed that by increasing the wheel width with the stock tire size handling was greatly improved!!! In contrast, my competitors ran 6” & 7” wheels with wider tires. I am sure they had LOWER grip with the wider tires.
My second advantage was I ran on Yokohama A008Rs while my competitors ran on BF Goodrich tires. I suspect the solid rubber shoulder of the Yokes gave me an advantage over the BFGs which had stylish grooves.
The nest issue is tire diameter. Yes, you can reduce tire diameter with smaller diameter wheels BUT can you get the highest performance tires in 15” diameter?
With stick diameter tires I could run up to 40 MPH in first gear. For most
autocrosses I would run completely in 1st gear. Smaller dia tires would give faster acceleration but I would lose time shifting back and forth from 1st to 2nd gear throughout the course.
Regards,
George
In sunny Arizona
