larger wheels = worse performance?
03-29-2001, 02:32 PM
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VERY interesting issue in the Spring 2001 issue of 'Honda Tuning' about the effect of larger wheels on power.
First the background:
They dyno tested a car (civic dx) with stock wheels and tires (185/70R-13 weighing 29 lbs).
They then swapped out the stock wheels and tires for 17" wheels and tires (205/40ZR-17 weighing 38.5 lbs).
Upgraded combo added 9.5 lbs (@33%), and increased circumference by 1.75" (@.25%).
At peak HP dropped from 113.6 HP to 109.8 HP (-3.8HP) with the largest difference being 7 HP. That's a loss of between @3% and @5%.
They conclusion was that this loss was caused by BOTH increased size AND increased weight. The size changed the effective gear ration resulting in increased effort to turn the wheels and decreased acceleration. The weight caused the car to struggle at the moment of inertia and to use more power to keep the drive wheels turning.
Extending this to the S2000, with similar increases in weight and size we would see a loss of somewhere between 9 HP and 12 HP.
I, for one, would love to see results that differentiate size related power loss from weight related power loss.
Regardless, if this is (in fact) correct it's a thought provoker for sure.
First the background:
They dyno tested a car (civic dx) with stock wheels and tires (185/70R-13 weighing 29 lbs).
They then swapped out the stock wheels and tires for 17" wheels and tires (205/40ZR-17 weighing 38.5 lbs).
Upgraded combo added 9.5 lbs (@33%), and increased circumference by 1.75" (@.25%).
At peak HP dropped from 113.6 HP to 109.8 HP (-3.8HP) with the largest difference being 7 HP. That's a loss of between @3% and @5%.
They conclusion was that this loss was caused by BOTH increased size AND increased weight. The size changed the effective gear ration resulting in increased effort to turn the wheels and decreased acceleration. The weight caused the car to struggle at the moment of inertia and to use more power to keep the drive wheels turning.
Extending this to the S2000, with similar increases in weight and size we would see a loss of somewhere between 9 HP and 12 HP.
I, for one, would love to see results that differentiate size related power loss from weight related power loss.
Regardless, if this is (in fact) correct it's a thought provoker for sure.
03-29-2001, 04:56 PM
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IMHO
i'd say more due to the changing ratio. compare to what people have said about changing final drive gear ratio, or like randy who put in a whole new gear set.
gears are like levers, have the right ones and you can move the earth!
i'd say more due to the changing ratio. compare to what people have said about changing final drive gear ratio, or like randy who put in a whole new gear set.
gears are like levers, have the right ones and you can move the earth!
03-29-2001, 06:34 PM
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malachi,
That's why you get lightweight wheels and tires of the same diameter.
Stock 16x7.5 with 225/50/16, S02's
-24.8 inch diameter
-42lb.
Volk Racing TE37 18x8.5 with 245/35/18, Toyo Proxes T1-S
-24.8 inch diamter
-38lb.
Scott and I swear we can feel a difference in acceleration between stock and our TE37's. ITR has driven my car and he tells me that it feels a bit faster that his. The lightweight wheels make a difference when I am already mooving, but the downside is that I get a better launch out of the stock tires.
That's why you get lightweight wheels and tires of the same diameter.
Stock 16x7.5 with 225/50/16, S02's
-24.8 inch diameter
-42lb.
Volk Racing TE37 18x8.5 with 245/35/18, Toyo Proxes T1-S
-24.8 inch diamter
-38lb.
Scott and I swear we can feel a difference in acceleration between stock and our TE37's. ITR has driven my car and he tells me that it feels a bit faster that his. The lightweight wheels make a difference when I am already mooving, but the downside is that I get a better launch out of the stock tires.
03-29-2001, 06:44 PM
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Spoon wheels look pretty cool.
If you really want the lightest 16's on the market...check out the Racing Hart CP035's.
The 16's weigh ~ 10 pounds. But, I have heard that the Racing Hart wheels dent easier...but, with 16's...I don't think that will be a big problem.
http://www.racinghart.com/wheel.asp?mkid=20&mdlid=113
They have 16x7 (front) and 16x7.5 (rear). I called them up one day to check if they had high offsets, and they said they could get them.
If you really want the lightest 16's on the market...check out the Racing Hart CP035's.
The 16's weigh ~ 10 pounds. But, I have heard that the Racing Hart wheels dent easier...but, with 16's...I don't think that will be a big problem.
http://www.racinghart.com/wheel.asp?mkid=20&mdlid=113
They have 16x7 (front) and 16x7.5 (rear). I called them up one day to check if they had high offsets, and they said they could get them.
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03-30-2001, 05:32 AM
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No, no, no!!!
Correct me if I am wrong, but weren't the stock Civic wheels only 13"? And the aftermarket wheels they tested were 17"?
That's a +4 increase!!!!
We are only talking a +1 (to 17") or +2 (to 18") increase on the S2000 here, so the differential loss between the two wheels should be MUCH lower than what they gotin the magazine test. This test is a good indicator, but I'd likely half the figure they got, maybe even less.
In my own opinion, I'd much prefer the extra grip and steering response provided by wider tires/thinner sidewall, plus the aesthetic improvement, and lose a few HP, than have the smaller wheels.
Cheers,
Correct me if I am wrong, but weren't the stock Civic wheels only 13"? And the aftermarket wheels they tested were 17"?
That's a +4 increase!!!!
We are only talking a +1 (to 17") or +2 (to 18") increase on the S2000 here, so the differential loss between the two wheels should be MUCH lower than what they gotin the magazine test. This test is a good indicator, but I'd likely half the figure they got, maybe even less.
In my own opinion, I'd much prefer the extra grip and steering response provided by wider tires/thinner sidewall, plus the aesthetic improvement, and lose a few HP, than have the smaller wheels.
Cheers,
03-30-2001, 08:07 AM
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+1 or +4, the increase in wheel circumferance was (unless my math is incorrect) only 0.25% - i've seen similar increases for people going from 16 to 17.