rim/tire weight makes a huge diff! wow!
Joined: Nov 2003
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From: WA
Originally Posted by doorman,Dec 4 2004, 02:03 PM
I remember those rims. I had the right of first refusal on those. We were both trying to get these rims. The guy told me that somebody else bought these from ebay and he had to sell them. 
You had the first chance to purchase them which you got. You don't have the right of first refusal. You snooze you lose. You can't expect a seller to hold something for days while you think if you really want them or not. Especially when their are others that know they want it.
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From: Dallas
Originally Posted by AlanP,Dec 7 2004, 04:00 AM
I found this thread very interesting. I'd like to speculate a little further...
Adding 50 lbs to an S2000 changes the horsepower-to-weight ratio by only about 1.5%. I think only the very most discerning and skillful driver would notice the 1.5% change in straight-line acceleration.
However, increasing the rotational inertia of each wheel might make a noticeable difference when entering a turn at higher speeds. While horsepower-to-weight might increase by only 1.5%, you might get a 10% increase in rotational inertia -- and that means the angular momentum of the car wheels increases by 10% at any given speed. Now when you hit a corner, it takes a larger torque from the steering assembly to change the angular momentum of the wheels. I'm not talking about the torque developed by the engine; I'm talking about the torque required by the driver to change the direction of the car.
The bottom line is that I would expect almost no difference in straight line acceleration, but a more significant difference in how the car feels when cornering. The difference would be more pronounced when cornering at high speeds.
Adding 50 lbs to an S2000 changes the horsepower-to-weight ratio by only about 1.5%. I think only the very most discerning and skillful driver would notice the 1.5% change in straight-line acceleration.
However, increasing the rotational inertia of each wheel might make a noticeable difference when entering a turn at higher speeds. While horsepower-to-weight might increase by only 1.5%, you might get a 10% increase in rotational inertia -- and that means the angular momentum of the car wheels increases by 10% at any given speed. Now when you hit a corner, it takes a larger torque from the steering assembly to change the angular momentum of the wheels. I'm not talking about the torque developed by the engine; I'm talking about the torque required by the driver to change the direction of the car.
The bottom line is that I would expect almost no difference in straight line acceleration, but a more significant difference in how the car feels when cornering. The difference would be more pronounced when cornering at high speeds.
the root of the big wheel/little wheel is not weight.... its rotational inertia (as someone mentioned earlier)
the physics equation has 4 constituents
k, m, r, i
where k is some constant......> m is the mass of the wheel....> r is the radius and i is the moment of inertia
the relationship is thus:
i = km(r^2)
what this means is that even though you have a larger wheel that may weigh the same as a smaller wheel the radius is the more important factor...
a 20" wheel that weighs 10 lbs has TWICE the moment of inertia as a 10" wheel that weighs 20 lbs...
moment of inertia is not only related to resistance to rotational acceleration..... but to changes in rotational direction...> in other words the wheel with the smaller moment of inertia will offer better steering response as well as better acceleration.... a few examples i can offer here are thus>
> ever take the front wheel off a bicycle, hold it by either side of the axle, and spin the wheel as fast you can..... and try to change the direction... the wheel will naturally resist this
>try the same test with a smaller wheel .....and the resistance is vastly reduced...
the second and more relevant example> polar moment of inertia in a car> the steering response from the moment of inertia of the wheel acts IDENTICALLY to the rotational responsiveness of a mid-engine car..... its because the weight is more centrally located. The same concept can apply to the chassis of the S2000, given the bulk of the weight is placed behind the front axle, giving it a 50/50 weight distribution.
yes, the tire may be one of the heavier portions of the unsprung mass of the car.... but even moving the sidewall inwards by making it taller... you are putting more "air" at the outside of the equation... effectively reducing the "r" portion for most of the individual portions of mass, of the rotating wheel/tire combo.......
nevermind that having a taller sidewall allows more forgiving handling... reducing the breakaway speed and making the car more controllable & predictable at the limit....
Go wider
Go Lighter ....but not bigger
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From: Atlanta
Originally Posted by MaxGeek,Dec 8 2004, 03:18 PM
Sorry I was told that you need more time to think about it. So he sold them to me a few days later.
You had the first chance to purchase them which you got. You don't have the right of first refusal. You snooze you lose. You can't expect a seller to hold something for days while you think if you really want them or not. Especially when their are others that know they want it.
You had the first chance to purchase them which you got. You don't have the right of first refusal. You snooze you lose. You can't expect a seller to hold something for days while you think if you really want them or not. Especially when their are others that know they want it.
wasn't for you but rather for him and bad selling practices. Back to discussion at hand.
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How about the weight of a OEM 16" with S02, anyone knows?
Interesting discovery:
I just recieve a 16" snow tires and wheels package from tirerack. The tires are Blizzak LM22 and the wheels are sportline something.... the weight is a little more than 40lbs per wheel.
My 18" OZ superleggera race silver and S03 weight about the same.
It proves that the cheapo sportline ( $100 per wheel) is just heavy.
Just my 2 cents.
Interesting discovery:
I just recieve a 16" snow tires and wheels package from tirerack. The tires are Blizzak LM22 and the wheels are sportline something.... the weight is a little more than 40lbs per wheel.
My 18" OZ superleggera race silver and S03 weight about the same.
It proves that the cheapo sportline ( $100 per wheel) is just heavy.
Just my 2 cents.
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Joined: Dec 2004
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From: Maple Grove, MN
it's unsprung weight bud. any weight to the outside of the hub will hurt your car.
"Sprung" weight is a term used to describe the parts of an automobile that are supported by the front and rear springs. They suspend the vehicle's frame, body, engine, and the power train above the wheels. These are quite heavy assemblies. The "unsprung" weight includes wheels and tires, brake assemblies, the rear axle assembly, and other structural members not supported by the springs.
Unsprung weight is a measurement of the weight of everything outboard of the wishbones or suspension links, plus 1/2 of the weight of the wishbones or links and spring/shock. It has a great effect on handling.
The more weight outboard of the car, the more force bumps exert on the suspension (and ultimately the chassis). This force must be dealt with using springs, dampers and anti-roll bars, and the more force, the more difficult it is to keep the tire planted on the road. This is especially true of lighter weight cars. If the car weighs 1000 lbs, a 2G bump would result in a vertical force of 10% of the car's weight. This will at the very least reduce the grip of the car, because the weight of the car is what keeps the tire planted, and pushing a car up into the air with that much force will inevitably reduce the weight on the tire, and hence grip.
Unsprung weight, or the weight comprised by tire, wheel and suspension affects how well the tire follows the bumps and dips in the road surface. Using lighter wheels, tires, uprights, wishbones or control arms, and other parts will reduce the weight. The weight of these suspension parts by itself is not so critical as the ratio between the car's sprung weight (chassis, driver, engine, etc) and the unsprung weight. The lower the unsprung weight in relation to the sprung weight, the easier it will be to control the tire/wheel via the springs, dampers (shocks) and anti-roll bars.
I hope this all made sense to you. basically, find a wheel combo that weights as light as possible..tehy will be pricey, but they will perform great. the smaller sidewall of a larger tire will give you more lateral grip (I explained that in another area of the forum) and they will just plain look cooler..I have a list here of wheels, and their approximate weights..I'll post them in a few following lists..good luck.
-A. Swift
"Sprung" weight is a term used to describe the parts of an automobile that are supported by the front and rear springs. They suspend the vehicle's frame, body, engine, and the power train above the wheels. These are quite heavy assemblies. The "unsprung" weight includes wheels and tires, brake assemblies, the rear axle assembly, and other structural members not supported by the springs.
Unsprung weight is a measurement of the weight of everything outboard of the wishbones or suspension links, plus 1/2 of the weight of the wishbones or links and spring/shock. It has a great effect on handling.
The more weight outboard of the car, the more force bumps exert on the suspension (and ultimately the chassis). This force must be dealt with using springs, dampers and anti-roll bars, and the more force, the more difficult it is to keep the tire planted on the road. This is especially true of lighter weight cars. If the car weighs 1000 lbs, a 2G bump would result in a vertical force of 10% of the car's weight. This will at the very least reduce the grip of the car, because the weight of the car is what keeps the tire planted, and pushing a car up into the air with that much force will inevitably reduce the weight on the tire, and hence grip.
Unsprung weight, or the weight comprised by tire, wheel and suspension affects how well the tire follows the bumps and dips in the road surface. Using lighter wheels, tires, uprights, wishbones or control arms, and other parts will reduce the weight. The weight of these suspension parts by itself is not so critical as the ratio between the car's sprung weight (chassis, driver, engine, etc) and the unsprung weight. The lower the unsprung weight in relation to the sprung weight, the easier it will be to control the tire/wheel via the springs, dampers (shocks) and anti-roll bars.
I hope this all made sense to you. basically, find a wheel combo that weights as light as possible..tehy will be pricey, but they will perform great. the smaller sidewall of a larger tire will give you more lateral grip (I explained that in another area of the forum) and they will just plain look cooler..I have a list here of wheels, and their approximate weights..I'll post them in a few following lists..good luck.
-A. Swift
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From: Santa Clara
Originally Posted by MaxGeek,Dec 8 2004, 12:28 PM
I think you would get a difference in straight line speed. (one larger then 1.5%)
Say you save 5lbs per wheel and tire combo and that wheel sizes are the same. (Not uncommon for forged vs cast)
5 x 4 = 20lbs. Someone earlier said every 1lb of unsprung weight = about 7lbs normal weight. so 20lb x 7 = 140lbs. Its said that losing about 14lbs on this car is about the same effect as gaining 1hp. So 140/14 = 10hp. Not saying you'll feel it but its larger then the 1.5% you said.
Say you save 5lbs per wheel and tire combo and that wheel sizes are the same. (Not uncommon for forged vs cast)
5 x 4 = 20lbs. Someone earlier said every 1lb of unsprung weight = about 7lbs normal weight. so 20lb x 7 = 140lbs. Its said that losing about 14lbs on this car is about the same effect as gaining 1hp. So 140/14 = 10hp. Not saying you'll feel it but its larger then the 1.5% you said.
Increasing the weight of a 2850 lb car by 50 lbs increases the weight by about 1.7%. So the horsepower-to-weight ratio decreases by 1.7%. I don't think many drivers would feel a difference in straight-line acceleration. Can you feel the difference with two or three bags of groceries in the trunk?