Effect of light weight wheels and tires on acceleration

cahouston

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Hello all,
I have searched here and Googled and have found very little real-world acceleration test results for the difference between heavier and lighter wheel and tire combinations. Most of what I have read has been rules of thumb, estimates, and repeated figures with no actual data to back it up.

Does anyone have real world acceleration data for 0-60 or 1/4 mile et comparing stock wheels/tires with light weight wheels/tires? Same day, same surface, same tires with only change being the wheels would be best.

I currently have the PP1 wheels with stock size MPS4S. When the tires are done, I plan to go with either the MPS4S or Indy 500s for the front and Nitto 555RII (275/40-19) for the rear. I am also looking at the SVE R357 19x10s for front and rear with one of the above front tires (265/40-19 front) and Nitto 555RII 275/40-19 for rear. That combination would reduce weight by ~10lbs per corner in the front and ~12.5lbs per corner in the rear.

Everyone says lighter wheels improve acceleration but I'd like to see some comparative data if anyone has any. I found one mathematical discussion involving rotational inertia and mass which concluded you get 2:1 benefit for tire weight reduction versus sprung weight reduction and 1.6:1 benefit for wheel weight reduction.

 

sk47

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Julius Sumner Miller: Lesson 12 - The Strange Behavior of Rolling Things - YouTube

Hello; Decades ago I used videos made by Professor Miller in classrooms. You question made me think of him. On the off chance his videos might be on line I did a search. There they were.

I picked the one closest to your question. There are some important bits around the 9 to 10 minute mark.

I have an idea how to answer your question but will do some thinking and checking first. These sorts of things can get confusing. I might suggest you do some research on engine flywheels for a clue. I sort of recall that there are racing flywheels which are configured to allow for quicker RPM change.
 

sk47

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How Does Wheel Size Affect Performance? (carthrottle.com)
Hello; Did another quick search. Found this.

Had a thought or two. If you ride bicycle with changeable gearing that might be a clue.

Also thought about the front wheels of pure drag cars. There is a reason why they are so small an skinny.

I guess it will be a trade off between the drive wheels needing traction and the power it takes to rotate a wheel/tire combo.
 
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cahouston

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How Does Wheel Size Affect Performance? (carthrottle.com)
Hello; Did another quick search. Found this.

Had a thought or two. If you ride bicycle with changeable gearing that might be a clue.

Also thought about the front wheels of pure drag cars. There is a reason why they are so small an skinny.

I guess it will be a trade off between the drive wheels needing traction and the power it takes to rotate a wheel/tire combo.
I will spend some time watching the video from your first reply. As for this link, it does make sense though for my question, the overall diameters of the wheels/tires will remain the same or very similar. The primary difference would be weight of wheel/tire and potentially a minimal increase in the contact patch size for the front tires.
 

sk47

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Hello; The front tires of a drag race car do very little with regard to the acceleration other than they need to use the least amount of energy. . So I think they tend to be as light weight as is possible and still be strong enough to support the vehicle. They are skinny to have a small contact patch is my guess so less friction and I guess less aerodynamic drag. My guess is the front tires diameter got smaller over time to reduce resistance of rotating as they accelerate.

The drive tires on the rear are much more complex.
 


Glenn 70

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Hello all,
I have searched here and Googled and have found very little real-world acceleration test results for the difference between heavier and lighter wheel and tire combinations. Most of what I have read has been rules of thumb, estimates, and repeated figures with no actual data to back it up.

Does anyone have real world acceleration data for 0-60 or 1/4 mile et comparing stock wheels/tires with light weight wheels/tires? Same day, same surface, same tires with only change being the wheels would be best.

I currently have the PP1 wheels with stock size MPS4S. When the tires are done, I plan to go with either the MPS4S or Indy 500s for the front and Nitto 555RII (275/40-19) for the rear. I am also looking at the SVE R357 19x10s for front and rear with one of the above front tires (265/40-19 front) and Nitto 555RII 275/40-19 for rear. That combination would reduce weight by ~10lbs per corner in the front and ~12.5lbs per corner in the rear.

Everyone says lighter wheels improve acceleration but I'd like to see some comparative data if anyone has any. I found one mathematical discussion involving rotational inertia and mass which concluded you get 2:1 benefit for tire weight reduction versus sprung weight reduction and 1.6:1 benefit for wheel weight reduction.
On the drag strip 1-2 tenths and 1-2 mph . That’s lighter rims same as factory size . A bit more with front runners . That was on my 2016 S550 .
 

K4fxd

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I lost 14 lbs of unsprung weight by using 2 piece rotors on a base GT. The lighter rotors were 1 MPH and .1 ET slower. 1/4 mile. Now these were a season apart and the air might have been great on the old rotors and crap on the light rotors.

I don't think I'm going to do a rotor compare.

The 2 piece rotors work better on road courses and on the street due to better cooling.
 
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cahouston

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I lost 14 lbs of unsprung weight by using 2 piece rotors on a base GT. The lighter rotors were 1 MPH and .1 ET slower. 1/4 mile. Now these were a season apart and the air might have been great on the old rotors and crap on the light rotors.

I don't think I'm going to do a rotor compare.

The 2 piece rotors work better on road courses and on the street due to better cooling.
I found a post on corvette forum about a C&D magazine article covering a comparison of the GT350 and GT350R. I could not find the actual data from that article direct from C&D but this is what the poster said from back in 2017:

"C&D magazine articles credit the CF 18-lb GT350R wheels for reducing 0-60 times by .4 seconds than standard aluminum GT350 rims. The lighter-wheel Qtr-mile times are reduced by .3 of a second. Lateral G numbers are 10.9% better with the lighter wheels (.98G vs 1.1G for 350 vs 350R). Braking distance was reduced from 152 to 146 feet."

The weight difference for that test was 29.5% where the wheels/tires I am looking at would be ~18.5% lighter so even if the C&D results were ONLY due to the wheel/tire weight, I would see less gains than they did.
 

TeeLew

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It's a small enough of a difference that it may be lost in the noise of your measurement. We can still calculate it and we know logically that it's a performance advantage, but you may not have the precision to measure it.
 

sk47

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You can feel it in the turns. I have vbox data that shows the difference. Obviously losing unsprung weight is a big plus
Hello; decades ago I worked on a jaguar sedan. It had inboard brakes at the rear. The brake rotors were near the differential rather than being out near the wheels. This was to reduce un-sprung weight. A measure which helps in handling and cornering.

I am not so sure this is what the OP is looking for. Reducing un-sprung weight helps the shocks and springs control wheel bounce and keeps the car more planted in curves. IRS also does the same. I had a car with IRS and could go around a washboard curve much faster in that car that a solid rear axle car. The solid axel car would skitter at the rear, where as the IRS car was planted as the outside wheel was not hitting the washboards. I think the OP is interested in straight line drag race sort of applications.
 

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When I researched this years ago my take away is that it predominantly helped at lower speed acceleration/deceleration, so starting from a stop or the last few feet of braking. The slower rate the wheel spin is accelerating at higher road speeds meant the gain from lighter wheels was negligible. I don't remember the exact math (wish I did).

The GT350/GT350R wheel weight comparison is apples to oranges, because those cars also ran very different tire compounds. Of course its going to accelerate and grip better with Sport Cup 2s versus MP4S. That's not all from wheel weight, probably very little is from wheel weight.
 

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I found a post on corvette forum about a C&D magazine article covering a comparison of the GT350 and GT350R. I could not find the actual data from that article direct from C&D but this is what the poster said from back in 2017:

"C&D magazine articles credit the CF 18-lb GT350R wheels for reducing 0-60 times by .4 seconds than standard aluminum GT350 rims. The lighter-wheel Qtr-mile times are reduced by .3 of a second. Lateral G numbers are 10.9% better with the lighter wheels (.98G vs 1.1G for 350 vs 350R). Braking distance was reduced from 152 to 146 feet."

The weight difference for that test was 29.5% where the wheels/tires I am looking at would be ~18.5% lighter so even if the C&D results were ONLY due to the wheel/tire weight, I would see less gains than they did.
Wait. So, they dropped 0.4sec off 0-60 but only 0.3 from the full 1/4 mile? What did the car get slower on the top end with lighter wheels or something?

I also find it odd the GT350 had a lower skid pad than a 2000 Cobra R.
 
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cahouston

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Wait. So, they dropped 0.4sec off 0-60 but only 0.3 from the full 1/4 mile? What did the car get slower on the top end with lighter wheels or something?

I also find it odd the GT350 had a lower skid pad than a 2000 Cobra R.
Yeah, I agree, I wish I could see the data behind their testing. The archived article I found from C&D did not include the actual data nor did it say anything about swapping wheels as the rest or like @NightmareMoon said, just took as an apples to oranges comparison with different tire compound.

All this to say is why I was hoping someone had real world experience.

I am referring mostly to drag racing for the acceleration part of my question.
 

TeeLew

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Wait. So, they dropped 0.4sec off 0-60 but only 0.3 from the full 1/4 mile? What did the car get slower on the top end with lighter wheels or something?

I also find it odd the GT350 had a lower skid pad than a 2000 Cobra R.
You're getting entirely too caught up in magazine numbers.
 

 
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