How bad of a difference do heavy wheels really make???..
04-21-2001, 06:50 PM
#1
I always see people with chrome or 18's or 19's talk about how their rims slow them down, and get them poor times at the track... How much of a difference do they really make?
Is there some sort of formula or way to calculate how bad it would be? How much heavier can they be then stock for you to still get reasonable or unnoticeable acceleration?
I am about to get some 2000 SE/GLE 16 X 6.5" rims.. They are 20 lbs each. How much would that slow me down? Would I really notice the extra 3-4 lbs per wheel I will pick up? Diameter will remain the same, since the tire is 50 series in profile...
so would 4 or maybe 5 extra lbs per wheel compared to stock make a big difference? What would that throw my 1/4 time off by?
thanks....
Is there some sort of formula or way to calculate how bad it would be? How much heavier can they be then stock for you to still get reasonable or unnoticeable acceleration?
I am about to get some 2000 SE/GLE 16 X 6.5" rims.. They are 20 lbs each. How much would that slow me down? Would I really notice the extra 3-4 lbs per wheel I will pick up? Diameter will remain the same, since the tire is 50 series in profile...
so would 4 or maybe 5 extra lbs per wheel compared to stock make a big difference? What would that throw my 1/4 time off by?
thanks....
04-21-2001, 07:10 PM
#3
Basically, the thing that will determine how much of an impact a wheel has on accleration is the moment of inertia. For a wheel + tire combination, most of the weight is at the radius, furthest from the axis of rotation. The moment of inertia is proportional to the mass multiplied by the radius squared. So, as the radius increases, the moment of inertia (I) goes up squared. The mass also causes I to increase. So, changes to the radius or mass results in big changes to I. Now, knowing the moment of inertia, we can look at the equation for torque, tau = I * alpha. tau = torque, I = moment of inertia, and alpha = angular acceleration. Using this, we can see that a larger I will require more and more torque to reach a certain angular acceleration. Thus, the engine must be able to produce more torque to achieve a certain acceleration.
But, the handling benefits of larger wheels can not be ignored
But, the handling benefits of larger wheels can not be ignored
04-21-2001, 07:14 PM
#5
Aren't you sorry you asked now!
Originally posted by UMD_MaxSE
Basically, the thing that will determine how much of an impact a wheel has on accleration is the moment of inertia. For a wheel + tire combination, most of the weight is at the radius, furthest from the axis of rotation. The moment of inertia is proportional to the radius squared. So, as the radius increases, the moment of inertia (I) goes up squared. So, changes to the radius results in big changes to I. Now, knowing the moment of inertia, we can look at the equation for torque, tau = I * alpha. tau = torque, I = moment of inertia, and alpha = angular acceleration. Using this, we can see that a larger I will require more and more torque to reach a certain angular acceleration. Thus, the engine must be able to produce more torque to achieve a certain acceleration.
But, the handling benefits of larger wheels can not be ignored
Basically, the thing that will determine how much of an impact a wheel has on accleration is the moment of inertia. For a wheel + tire combination, most of the weight is at the radius, furthest from the axis of rotation. The moment of inertia is proportional to the radius squared. So, as the radius increases, the moment of inertia (I) goes up squared. So, changes to the radius results in big changes to I. Now, knowing the moment of inertia, we can look at the equation for torque, tau = I * alpha. tau = torque, I = moment of inertia, and alpha = angular acceleration. Using this, we can see that a larger I will require more and more torque to reach a certain angular acceleration. Thus, the engine must be able to produce more torque to achieve a certain acceleration.
But, the handling benefits of larger wheels can not be ignored
I was bored 
dunno if the spacers are the answer
04-21-2001, 09:15 PM
#10
Senior Member
Join Date: Oct 2000
Posts: 1,493
I'm not sure if there is a corelation or not, but my friend had a set of stock 17" GS400 wheels on his car and came across a set of light weight 17" wheels with the same tires and all. Apparently the ride was smoother and felt more solid with the stock wheels. He gave his stock wheels up to me and got himself a set of 18's...so we're both happy.
04-21-2001, 09:43 PM
#11
uhh
UMD Max, 
sorry I asked..
Brubenstein, thank you, that was what I was looking for, not that I race my car or anything...
20 lbs per wheel, compared to the 15-16? stock ... tire + wheel combo of 16's = 44-46 lbs..... stock 36-39? Not too bad, I've driven with 30 pound 17 inch rims, so 20 will seem cool..
Big Brakes, no thanks, I'm good for now
sorry I asked.. Brubenstein, thank you, that was what I was looking for, not that I race my car or anything...
20 lbs per wheel, compared to the 15-16? stock ... tire + wheel combo of 16's = 44-46 lbs..... stock 36-39? Not too bad, I've driven with 30 pound 17 inch rims, so 20 will seem cool..
Big Brakes, no thanks, I'm good for now
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