Setup for a fast street/track S2000 - Part II Tires
04-24-2004, 11:37 AM
#1
Administrator
Thread Starter
In the first part of this series of threads I mentioned that there was no single change or mod we made to make the car as fast as it is. Tires were a big part of the equation and I'll talk about them here. My teammates may jump in later to expand upon what I've said or add information I forgot.
The tires we chose were 3 sets of Sumitomo HRTZ 245/45R17 front, 275/40R17 rear shaved to 4/32nds tread depth. I was very impressed by these tires not only because of the price but also how well behaved they were, how grippy they were and how well they held up to track use. The tread blocks are smaller than the BFG KD tires and they probably aren't as grippy but the benefit of having 3 full sets for less than the price of 2 sets of KDs was worth it. Quantity has a quality all it's own as they say.
The tires are best fresh. In retrospect I think I would have shaved 2 of the sets to 2/32nd and one to 4/32nds. They were fast for 2 sessions when new and then tapered off. Having 3 sets meant we didn't need to run any one set for more than 2 days. We swapped them back and forth to keep the best for the sessions we needed to run fast.
For us even tire wear wasn't a big problem. Since the tires were only going to be used for a short time it didn't matter if they wore unevenly. Most of them wore in the middle and the inside edge, mainly due to the camber we were carrying.
For wheels we went with Volks CE28N in 17 inch. They are a strong light weight wheel and they look good. I purchased a set and we borrowed another set from Asura (thanks!!). 18 inch CCW wheels would have been better but finding tires to fit was a real problem. The Volks were also in stock which would have been a logistical nightmare otherwise.
For tire pressures we started the week with 34-35 psi all around. This seemed like a logical starting point based on our experience albeit with DOT-R tires. We had no real complaints but we weren't exactly turing fast laps either. On day 2 at Willow Springs we swapped the left hand tires for a new ones. JP went out in the 3rd session to scrub them in and then Dave went out in session 4 to turn hot laps. Hot laps is what we got! He clicked off some phenomenal times shattering all others.
What we didn't do however was check the tire pressures of the new tires!
When we measured them after the final session we had 35 psi in the right and 42-48 psi in the left!! Dave made the comment to us that the setup was just about perfect and that the car tracked really well in the fast right handers of Willow Springs. It seems we had discovered what the NASCAR guys have known for a long time. Asymmetrical tire pressures is a good thing. For the rest of the week we ran the pressures on the outside tires 4-5 psi hot higher than the inside tires. This makes the outside tires bigger and tracks the car toward the apex with throttle.
The other thing we discovered was the street tires really like a lot of pressure. We changed our starting cold pressure to 35psi cold on the inside, 38psi cold on the outside. We were shooting for hot pressures of 40psi inside, 44psi outside. We didn't always get it depending on the track but that was the goal.
Wheels and tires was by in large the biggest budget items. A new set of wheels ran a little over $2000 and the tires were $550/set ($450 plus $100 to shave) or a total of $1650 for tires. There were all of the typical nickel and dime expenses of course bringing to total for wheels and tires to roughly $4000, almost half of the $10000 budget.
If you aren't running Sumitomo street tires you should be. They are available from the Tire Rack. The wheels are available from Evolution. In Part III I'm going to talk about our suspension setup. This is the area where we had the most flexibility for making change and where I think we made the biggest improvements.
The tires we chose were 3 sets of Sumitomo HRTZ 245/45R17 front, 275/40R17 rear shaved to 4/32nds tread depth. I was very impressed by these tires not only because of the price but also how well behaved they were, how grippy they were and how well they held up to track use. The tread blocks are smaller than the BFG KD tires and they probably aren't as grippy but the benefit of having 3 full sets for less than the price of 2 sets of KDs was worth it. Quantity has a quality all it's own as they say.
The tires are best fresh. In retrospect I think I would have shaved 2 of the sets to 2/32nd and one to 4/32nds. They were fast for 2 sessions when new and then tapered off. Having 3 sets meant we didn't need to run any one set for more than 2 days. We swapped them back and forth to keep the best for the sessions we needed to run fast.
For us even tire wear wasn't a big problem. Since the tires were only going to be used for a short time it didn't matter if they wore unevenly. Most of them wore in the middle and the inside edge, mainly due to the camber we were carrying.
For wheels we went with Volks CE28N in 17 inch. They are a strong light weight wheel and they look good. I purchased a set and we borrowed another set from Asura (thanks!!). 18 inch CCW wheels would have been better but finding tires to fit was a real problem. The Volks were also in stock which would have been a logistical nightmare otherwise.
For tire pressures we started the week with 34-35 psi all around. This seemed like a logical starting point based on our experience albeit with DOT-R tires. We had no real complaints but we weren't exactly turing fast laps either. On day 2 at Willow Springs we swapped the left hand tires for a new ones. JP went out in the 3rd session to scrub them in and then Dave went out in session 4 to turn hot laps. Hot laps is what we got! He clicked off some phenomenal times shattering all others.
What we didn't do however was check the tire pressures of the new tires!
When we measured them after the final session we had 35 psi in the right and 42-48 psi in the left!! Dave made the comment to us that the setup was just about perfect and that the car tracked really well in the fast right handers of Willow Springs. It seems we had discovered what the NASCAR guys have known for a long time. Asymmetrical tire pressures is a good thing. For the rest of the week we ran the pressures on the outside tires 4-5 psi hot higher than the inside tires. This makes the outside tires bigger and tracks the car toward the apex with throttle. The other thing we discovered was the street tires really like a lot of pressure. We changed our starting cold pressure to 35psi cold on the inside, 38psi cold on the outside. We were shooting for hot pressures of 40psi inside, 44psi outside. We didn't always get it depending on the track but that was the goal.
Wheels and tires was by in large the biggest budget items. A new set of wheels ran a little over $2000 and the tires were $550/set ($450 plus $100 to shave) or a total of $1650 for tires. There were all of the typical nickel and dime expenses of course bringing to total for wheels and tires to roughly $4000, almost half of the $10000 budget.
If you aren't running Sumitomo street tires you should be. They are available from the Tire Rack. The wheels are available from Evolution. In Part III I'm going to talk about our suspension setup. This is the area where we had the most flexibility for making change and where I think we made the biggest improvements.
04-24-2004, 01:07 PM
#2
Registered User
Join Date: Oct 2000
Location: Santa Cruz, CA
Posts: 1,664
Likes: 0
Received 0 Likes
on
0 Posts
A couple things to add, err beans to spill...
These are definetly Cheating Bastard tires and the cover story seems to have stuck.
We got a number of comments that confirmed this. The only person that seemed to figure out what was going on was Todd Southwell who was co-driving Richards car.
These tires are also alot of fun on the track, very preditable and progressive with their scream easily heard over the exhaust and engine noise. Their grip is just about on par with RA1s, and they have similar overheat recovery behaviour.
Pushing a car with asymetric tire pressures takes some getting used to. For instance on high speed sweepers like T9 and T2 at WS or riverside at BW you need to get on the gas to turn the nose into the turn. You might say "Well Duhh, power on oversteer" but thats not whats happening, the back end is hooked up and not letting go. Its the difference in rear tire diameters thats driving the nose into the turn. It should also be noted that when trailing off the throttle the nose will point out of the turn. Not an ideal situation when you feel like you need to scrub speed from a overly hot turn entry. At times i was forced to feed in power to rotate the car into the turn when every fiber in my body was telling me to do the opposite. Definetly takes some getting used to.
I've said it before and i'll say it again, I realy like the CE28Ns. They are just about ideal.
These are definetly Cheating Bastard tires and the cover story seems to have stuck.
We got a number of comments that confirmed this. The only person that seemed to figure out what was going on was Todd Southwell who was co-driving Richards car.These tires are also alot of fun on the track, very preditable and progressive with their scream easily heard over the exhaust and engine noise. Their grip is just about on par with RA1s, and they have similar overheat recovery behaviour.
Pushing a car with asymetric tire pressures takes some getting used to. For instance on high speed sweepers like T9 and T2 at WS or riverside at BW you need to get on the gas to turn the nose into the turn. You might say "Well Duhh, power on oversteer" but thats not whats happening, the back end is hooked up and not letting go. Its the difference in rear tire diameters thats driving the nose into the turn. It should also be noted that when trailing off the throttle the nose will point out of the turn. Not an ideal situation when you feel like you need to scrub speed from a overly hot turn entry. At times i was forced to feed in power to rotate the car into the turn when every fiber in my body was telling me to do the opposite. Definetly takes some getting used to.
I've said it before and i'll say it again, I realy like the CE28Ns. They are just about ideal.
04-24-2004, 10:20 PM
#4
Originally posted by davepk
A couple things to add, err beans to spill...
These are definetly Cheating Bastard tires... Their grip is just about on par with RA1s...
A couple things to add, err beans to spill...
These are definetly Cheating Bastard tires... Their grip is just about on par with RA1s...
Well, now I don't feel quite as bad about my times getting beat down so bad by guys on "street tires"!
04-24-2004, 10:49 PM
#5
Registered User
The track time/performance results posted on TireRack.com for the HTR Z and HTR Z II put them in the same category (with the similar performance) to ES 100s and Kumho 712s. The 712s pulled better lap times in their tests as well.
Comparable to RA1s? What am I missing?
Comparable to RA1s? What am I missing?
04-25-2004, 08:12 AM
#7
Registered User
Join Date: Oct 2000
Location: Santa Cruz, CA
Posts: 1,664
Likes: 0
Received 0 Likes
on
0 Posts
[QUOTE]Originally posted by Nobody
The track time/performance results posted on TireRack.com for the HTR Z and HTR Z II put them in the same category (with the similar performance) to ES 100s and Kumho 712s.
The track time/performance results posted on TireRack.com for the HTR Z and HTR Z II put them in the same category (with the similar performance) to ES 100s and Kumho 712s.
Trending Topics
04-25-2004, 08:52 AM
#8
[QUOTE]Originally posted by Nobody
The track time/performance results posted on TireRack.com for the HTR Z and HTR Z II put them in the same category (with the similar performance) to ES 100s and Kumho 712s.
The track time/performance results posted on TireRack.com for the HTR Z and HTR Z II put them in the same category (with the similar performance) to ES 100s and Kumho 712s.
04-26-2004, 01:25 PM
#10
Originally posted by cthree In Part III I'm going to talk about our suspension setup. This is the area where we had the most flexibility for making change and where I think we made the biggest improvements.
