Light wheels for autox performance - question
07-12-2006, 11:21 AM
#1
Light wheels for autox performance - question
Hi- I've been autocrossing a stock C4 for 3 years. Our events are 1.5 miles at a closed airport so the runs are pretty fast. Currently I run nitto RII's but I want to go a little faster, so I've been thinking about lighter wheels and v710's for next year.
Is there anyone here who has bought lighter wheels and saw significant performance improvements with them?
Any opinions on light wheels woudl be welcome.
thank you!
Is there anyone here who has bought lighter wheels and saw significant performance improvements with them?
Any opinions on light wheels woudl be welcome.
thank you!
07-12-2006, 01:36 PM
#2
Drifting
Speed costs money... how fast do you want to go... 
All kidding aside, I read an article a few years ago where heavier cast aluminum wheels were tested against lighter 3 piece wheels and it showed a few tenths difference in the 1/4 mile times. I think it was a Mustang used as the test vehicle.
Each wheel is a "flywheel" and requires torque to accelerate to increase or decrease speed (rpm). So a lighter wheel will not absorb as much of the torque available to accelerate the vehicle as a heavier wheel. More importantly is where the wheel weight is concentrated. You want a wheel that has most of it's mass in the spider and less at the outside diameter to reduce wheel torque requirements. Likewise a lighter tire will have a greater perfomance increase than a heavier tire.
Your biggest gain will be with a lighter tire. The center of mass for the tire is always farther out than the wheel. Stickier compound will help too.
A three piece wheel with a rolled rim will be the next biggest performance gain. If the wheel manufacturers published the WR^2 for their wheels, it would be an easy decision.
All kidding aside, I read an article a few years ago where heavier cast aluminum wheels were tested against lighter 3 piece wheels and it showed a few tenths difference in the 1/4 mile times. I think it was a Mustang used as the test vehicle.
Each wheel is a "flywheel" and requires torque to accelerate to increase or decrease speed (rpm). So a lighter wheel will not absorb as much of the torque available to accelerate the vehicle as a heavier wheel. More importantly is where the wheel weight is concentrated. You want a wheel that has most of it's mass in the spider and less at the outside diameter to reduce wheel torque requirements. Likewise a lighter tire will have a greater perfomance increase than a heavier tire.
Your biggest gain will be with a lighter tire. The center of mass for the tire is always farther out than the wheel. Stickier compound will help too.
A three piece wheel with a rolled rim will be the next biggest performance gain. If the wheel manufacturers published the WR^2 for their wheels, it would be an easy decision.
07-12-2006, 05:41 PM
#4
I have run a wheel/tire combination that was around 10lbs less/corner. The car accelerated significantly faster. The limited instruments we had showed around .1G more in 2nd gear. There were other issues with that combo, but it was quicker in a straight line.
If you can improve grip and reduce weight in the package, it is worth a measurable amount on the clock. I use around the 3-4lbs (approx 10% of the total wheel/tire weight) as the point where it is worth spending more to go lighter.
Tire rack has some very light SSR wheels in C4 sizes that would work well.
If you can improve grip and reduce weight in the package, it is worth a measurable amount on the clock. I use around the 3-4lbs (approx 10% of the total wheel/tire weight) as the point where it is worth spending more to go lighter.
Tire rack has some very light SSR wheels in C4 sizes that would work well.
07-12-2006, 07:22 PM
#5
Melting Slicks
Yes it makes a difference, it is small but you can feel it. So, how much is one or two tenths of a second worth (this coming from a guy who finished second at Nationals by .06 seconds on a car that had stock wheels)? The answer is "priceless".....if I had only done it then...
After that I figured anything that was an advantage was worth it....I used to have a set of the Corvette Challenge DiMags. If you put a set of Hoosiers on them they were amazingly light. As a gag I would sometimes ask one of my Corvette friends to "hand me that tire over there"... They would jerk the wheel up like they were lifting a stock wheel and darn near hit themselves in the forehead with it....
After that I figured anything that was an advantage was worth it....I used to have a set of the Corvette Challenge DiMags. If you put a set of Hoosiers on them they were amazingly light. As a gag I would sometimes ask one of my Corvette friends to "hand me that tire over there"... They would jerk the wheel up like they were lifting a stock wheel and darn near hit themselves in the forehead with it....
