Does Wheel Weight Loss vs Reg Car Weight Loss Affect Performance Differently?
05-11-09, 12:36 PM
#1
Pole Position
Thread Starter
Does Wheel Weight Loss vs Reg Car Weight Loss Affect Performance Differently?
I'm thinking about purchasing some aftermarket wheels for my 350. According to the vendor, they weigh 23.5 lbs Front, 25.9 lbs Rear. With the stock 18's weighing 28 lbs Fr, 30 lbs R, that's a difference of 17.2 lbs. (I understand the larger 19" tires will eat up some of that difference as well.)
I was wondering if anyone knows if wheel weight reduction affects performance differently than just shaving weight from somewhere off the vehicle. With these wheels having roughly 4 lbs less rotational mass off each corner, I assume that should allow the vehicle to turn the wheels more efficiently and consequently bolster performance. It only seems reasonable that this methodology would affect performance in more a positive way than just taking the same weight off the car. (remove spare tire, for example)
Or is weight reduction all the same, regardless of where it comes from?
With no real performance mods for the 350 that achieve major gains, I want to make certain not to add anything aftermarket to the car that slows down my ride.
No thugged out chrome 20's for me. Hell nah.
What do you all think?
I was wondering if anyone knows if wheel weight reduction affects performance differently than just shaving weight from somewhere off the vehicle. With these wheels having roughly 4 lbs less rotational mass off each corner, I assume that should allow the vehicle to turn the wheels more efficiently and consequently bolster performance. It only seems reasonable that this methodology would affect performance in more a positive way than just taking the same weight off the car. (remove spare tire, for example)
Or is weight reduction all the same, regardless of where it comes from?
With no real performance mods for the 350 that achieve major gains, I want to make certain not to add anything aftermarket to the car that slows down my ride.
No thugged out chrome 20's for me. Hell nah.
What do you all think?
05-11-09, 01:10 PM
#2
I'm thinking about purchasing some aftermarket wheels for my 350. According to the vendor, they weigh 23.5 lbs Front, 25.9 lbs Rear. With the stock 18's weighing 28 lbs Fr, 30 lbs R, that's a difference of 17.2 lbs. (I understand the larger 19" tires will eat up some of that difference as well.)
I was wondering if anyone knows if wheel weight reduction affects performance differently than just shaving weight from somewhere off the vehicle. With these wheels having roughly 4 lbs less rotational mass off each corner, I assume that should allow the vehicle to turn the wheels more efficiently and consequently bolster performance. It only seems reasonable that this methodology would affect performance in more a positive way than just taking the same weight off the car. (remove spare tire, for example)
Or is weight reduction all the same, regardless of where it comes from?
With no real performance mods for the 350 that achieve major gains, I want to make certain not to add anything aftermarket to the car that slows down my ride.
No thugged out chrome 20's for me. Hell nah.
What do you all think?
I was wondering if anyone knows if wheel weight reduction affects performance differently than just shaving weight from somewhere off the vehicle. With these wheels having roughly 4 lbs less rotational mass off each corner, I assume that should allow the vehicle to turn the wheels more efficiently and consequently bolster performance. It only seems reasonable that this methodology would affect performance in more a positive way than just taking the same weight off the car. (remove spare tire, for example)
Or is weight reduction all the same, regardless of where it comes from?
With no real performance mods for the 350 that achieve major gains, I want to make certain not to add anything aftermarket to the car that slows down my ride.
No thugged out chrome 20's for me. Hell nah.
What do you all think?
Reducing unsprung weight (your rims for example) absolutely has more impact than reducing sprung weight (the spare tire in the trunk for example)
05-11-09, 01:54 PM
#3
Some unsprung and semi-sprung weight is rotational and some is fixed. The wheels, brake rotors, and hubs are rotational. It takes a lot more energy to accelerate the wheels in a forward direction + in a spinning motion than would if you were just carrying them in your trunk. When you get up to speed, the mass of the wheels creates acts like a gyroscope, which has to be overpowered when you change direction and speed. These spinning forces are largely why lighter wheels can make such a noticeable performance impact. Mass towards the center has a lesser impact where mass towards the edge of the rim and tire has a greater impact. This can be VERY important when determining how much energy it takes to accelerate a certain wheel. If a 30lb wheel's mass was centered near the hub and a 20lb wheel center of mass was near the rim, the 30lbs wheel may require less energy to accelerate.
The non-rotating unsprung and semi-sprung parts are the brake calipers, control arm, and other suspension parts. These parts are not rotating, but they are moving as you drive over bumps in the road. When you hit a bump that pushes tire up it moves the wheel and suspension parts. Ideally the wheel would move up so quickly as to match the contour of the bump, but since the unsprung wheel and suspension parts has mass, the bump needs to exert energy to accelerate these parts up. If these parts were to have less mass, then your suspension would ride up the bump better and most importantly down the other side quicker. This would give you a better tire contact patch, better road holding, and a smoother ride over the bump, but lightening up the non-rotational mass probably will not give you a noticeable improvement in acceleration.
The general rule of thumb for unsprung mass & weight is for every 100lbs you lose, you might gain a hundredth on top of your quartermile elapsed time. Hardly worth it when you consider all the stuff you'd have to rip out to make any sort of noticeable difference.
The non-rotating unsprung and semi-sprung parts are the brake calipers, control arm, and other suspension parts. These parts are not rotating, but they are moving as you drive over bumps in the road. When you hit a bump that pushes tire up it moves the wheel and suspension parts. Ideally the wheel would move up so quickly as to match the contour of the bump, but since the unsprung wheel and suspension parts has mass, the bump needs to exert energy to accelerate these parts up. If these parts were to have less mass, then your suspension would ride up the bump better and most importantly down the other side quicker. This would give you a better tire contact patch, better road holding, and a smoother ride over the bump, but lightening up the non-rotational mass probably will not give you a noticeable improvement in acceleration.
The general rule of thumb for unsprung mass & weight is for every 100lbs you lose, you might gain a hundredth on top of your quartermile elapsed time. Hardly worth it when you consider all the stuff you'd have to rip out to make any sort of noticeable difference.
05-11-09, 04:07 PM
#6
Lexus Fanatic
So if I am reading above correctly, then the typical reductions in unsprung weight will have minimal and barely measurable impact on acceleration. Hopefully the impact is more noticeable on the ride/handling.
05-11-09, 05:38 PM
#7
Tech Info Resource
iTrader: (2)
A dynojet dyno (or any other inertial dyno) will tell you the lighter wheels make more power (even though they don't) because they accelerate better. There are only two downsides to very light wheels - they are usually (but not always) very expensive and they are usually (but not always) much more fragile than heavier wheels.
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05-11-09, 06:23 PM
#8
Pole Position
Thread Starter
It depends on where the mass is centered. If the wheel is very light at the rim it will take less energy to make it change its rotational speed. It also has the added effect of better wheel compliance if the entire wheel weighs less than the wheel being replaced. It can be VERY noticeable.
A dynojet dyno (or any other inertial dyno) will tell you the lighter wheels make more power (even though they don't) because they accelerate better. There are only two downsides to very light wheels - they are usually (but not always) very expensive and they are usually (but not always) much more fragile than heavier wheels.
A dynojet dyno (or any other inertial dyno) will tell you the lighter wheels make more power (even though they don't) because they accelerate better. There are only two downsides to very light wheels - they are usually (but not always) very expensive and they are usually (but not always) much more fragile than heavier wheels.
Some unsprung and semi-sprung weight is rotational and some is fixed. The wheels, brake rotors, and hubs are rotational. It takes a lot more energy to accelerate the wheels in a forward direction + in a spinning motion than would if you were just carrying them in your trunk. When you get up to speed, the mass of the wheels creates acts like a gyroscope, which has to be overpowered when you change direction and speed. These spinning forces are largely why lighter wheels can make such a noticeable performance impact. Mass towards the center has a lesser impact where mass towards the edge of the rim and tire has a greater impact. This can be VERY important when determining how much energy it takes to accelerate a certain wheel. If a 30lb wheel's mass was centered near the hub and a 20lb wheel center of mass was near the rim, the 30lbs wheel may require less energy to accelerate.
The non-rotating unsprung and semi-sprung parts are the brake calipers, control arm, and other suspension parts. These parts are not rotating, but they are moving as you drive over bumps in the road. When you hit a bump that pushes tire up it moves the wheel and suspension parts. Ideally the wheel would move up so quickly as to match the contour of the bump, but since the unsprung wheel and suspension parts has mass, the bump needs to exert energy to accelerate these parts up. If these parts were to have less mass, then your suspension would ride up the bump better and most importantly down the other side quicker. This would give you a better tire contact patch, better road holding, and a smoother ride over the bump, but lightening up the non-rotational mass probably will not give you a noticeable improvement in acceleration.
The general rule of thumb for unsprung mass & weight is for every 100lbs you lose, you might gain a hundredth on top of your quartermile elapsed time. Hardly worth it when you consider all the stuff you'd have to rip out to make any sort of noticeable difference.
The non-rotating unsprung and semi-sprung parts are the brake calipers, control arm, and other suspension parts. These parts are not rotating, but they are moving as you drive over bumps in the road. When you hit a bump that pushes tire up it moves the wheel and suspension parts. Ideally the wheel would move up so quickly as to match the contour of the bump, but since the unsprung wheel and suspension parts has mass, the bump needs to exert energy to accelerate these parts up. If these parts were to have less mass, then your suspension would ride up the bump better and most importantly down the other side quicker. This would give you a better tire contact patch, better road holding, and a smoother ride over the bump, but lightening up the non-rotational mass probably will not give you a noticeable improvement in acceleration.
The general rule of thumb for unsprung mass & weight is for every 100lbs you lose, you might gain a hundredth on top of your quartermile elapsed time. Hardly worth it when you consider all the stuff you'd have to rip out to make any sort of noticeable difference.
So who is right?
With my original scenario with about 4 lbs less on each corner with the aftermarket wheels, will the difference be tangible or better yet, noticeable?
05-11-09, 06:27 PM
#9
Lexus Fanatic
05-11-09, 09:40 PM
#10
Tech Info Resource
iTrader: (2)
SOTP? Probably not. Measured with a watch? Probably, and if you're talking about autocross, definitely.
05-12-09, 02:05 AM
#11
Pole Position
put it this way, for our cars u feel the gain from light weight wheels more than you would say adding an aftermarket axelback exhaust. My wheels are my best mod ive done.
05-12-09, 04:58 AM
#12
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yeah it makes a noticable differance i think. On my old car i switched out my stock rims for a cool pair of aftermarkets that were 5 pounds more then the stocks and it felt like i had lost 10hp. Also thats why it sucks to get a big aftermarket brake kit because the larger heavier rotor can cause you to lose hp (as measured on a dyno) ndk83 i would most definitly agree with. It will give you a more noticable feel then probaly any bolt on you can do!
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