Impact on performance due to wheel weight/size?
Thread Starter
Junior Member
Joined: Dec 2007
Posts: 39
Likes: 0
Bicycle
Impact on performance due to wheel weight/size?
Just a thought. If I were to replace my custom wheels which weight ~70lbs (with tires) with a lighter set (~50lbs, same diameter) would there be a significant increase in performance, in terms of acceleration? What about handling? I am guessing yes, but is it possible to quantify these gains mathematically?
Also, how heavy is the stock rear '03 CL55 wheel+tire?
Thanks guys.
Also, how heavy is the stock rear '03 CL55 wheel+tire?
Thanks guys.
Banned
Joined: Mar 2006
Posts: 2,855
Likes: 2
From: Southern California
S600TT, R350
Yes, there will be less losses going through the wheels and you will see more power at the wheels on acceleration type (i.e. Dynojet) dyno.
I have dynoed a lot of cars when switching wheels. Figure about 15-20 RWHP.
I have dynoed a lot of cars when switching wheels. Figure about 15-20 RWHP.
MBWorld Fanatic!
Joined: Feb 2004
Posts: 2,566
Likes: 7
'14 ML BT
Thread Starter
Junior Member
Joined: Dec 2007
Posts: 39
Likes: 0
Bicycle
More importantly, if we know the time history of the torque at the wheel, then we can compute the acceleration as follows from Newtons laws, Net_Torque = Inerita_of_Wheel?*Angular_Acceleration.
Then, what we really care about is translational acceleration which is just: Trans_acceleration=Radius*Angular_acceleration.
Below is a graph that I generated using some dyno numbers I dug up online for a stock '03 CL55. It compares Trans_acceleration of a 70lbs wheel+tire to a 50lbs wheel+tire.
I know for a fact that these numbers mean nothing as far as Acceleration comptuation is concerned. The reason being is that I don't know if the torque numbers are given for just one wheel or the entire rear setup (2 wheels / axles). In my calculations I only used inertia of one wheel, which I doubt is correct but gives you a back of the napkin type calculation.
Then certainly, in real life conditions, the net torque is not just what the dyno graph reads, we also have to account for friction between tire and contact surface if nothing else..?
Maybe a better way to calculate acceleration would be to use torque readings along with horsepower readings. Dividing hp by torque would give us velocity and then we could differentiate to obtain acceleration? Would be more realistic and we wouldnt have to worry about detailed modeling since we have empirical data.
MBWorld Fanatic!
Joined: Feb 2004
Posts: 2,566
Likes: 7
'14 ML BT
Here is what I know, horsepower is a measure of energy per second, it can be computed at any time (rev/rpm) if you know the time history of the torque and the velocity of the wheel. hp = torque x velocity.
More importantly, if we know the time history of the torque at the wheel, then we can compute the acceleration as follows from Newtons laws, Net_Torque = Inerita_of_Wheel?*Angular_Acceleration.
Then, what we really care about is translational acceleration which is just: Trans_acceleration=Radius*Angular_acceleration.
...
I know for a fact that these numbers mean nothing as far as Acceleration comptuation is concerned. The reason being is that I don't know if the torque numbers are given for just one wheel or the entire rear setup (2 wheels / axles). In my calculations I only used inertia of one wheel, which I doubt is correct but gives you a back of the napkin type calculation.
Then certainly, in real life conditions, the net torque is not just what the dyno graph reads, we also have to account for friction between tire and contact surface if nothing else..?
Maybe a better way to calculate acceleration would be to use torque readings along with horsepower readings. Dividing hp by torque would give us velocity and then we could differentiate to obtain acceleration? Would be more realistic and we wouldnt have to worry about detailed modeling since we have empirical data.
More importantly, if we know the time history of the torque at the wheel, then we can compute the acceleration as follows from Newtons laws, Net_Torque = Inerita_of_Wheel?*Angular_Acceleration.
Then, what we really care about is translational acceleration which is just: Trans_acceleration=Radius*Angular_acceleration.
...
I know for a fact that these numbers mean nothing as far as Acceleration comptuation is concerned. The reason being is that I don't know if the torque numbers are given for just one wheel or the entire rear setup (2 wheels / axles). In my calculations I only used inertia of one wheel, which I doubt is correct but gives you a back of the napkin type calculation.
Then certainly, in real life conditions, the net torque is not just what the dyno graph reads, we also have to account for friction between tire and contact surface if nothing else..?
Maybe a better way to calculate acceleration would be to use torque readings along with horsepower readings. Dividing hp by torque would give us velocity and then we could differentiate to obtain acceleration? Would be more realistic and we wouldnt have to worry about detailed modeling since we have empirical data.
So how 'bout them Celtics?
MBWorld Fanatic!
Joined: Feb 2004
Posts: 3,703
Likes: 5
From: Arizona
SL55AMG, Ferrari 348, Ferrari Testarossa, Ferrari F40, Ferrari Mondial t, Ducati 916, Indycar
Just a thought. If I were to replace my custom wheels which weight ~70lbs (with tires) with a lighter set (~50lbs, same diameter) would there be a significant increase in performance, in terms of acceleration? What about handling? I am guessing yes, but is it possible to quantify these gains mathematically?
Also, how heavy is the stock rear '03 CL55 wheel+tire?
Thanks guys.
Also, how heavy is the stock rear '03 CL55 wheel+tire?
Thanks guys.
Your car will accelerate better, but you will really notice how much more crisply the car turns in.
