Dyno Runs - The effects of wheel/tire weights on wheel horsepower article

[SIMSS]

I came across this article and wanted to ask what your thoughts are? Great that it's done on a Camaro SS.

Article with dyno graph came from http://teamspeed.com/forums/aventado...orsepower.html

Test:
Davenport Motorsports (Custom Performance Parts and Service : Davenport Motorsports) of Canada, wanted to see the dyno effects of running different wheels on cars. They took a factory 2012 Camaro SS and ran 3 dyno runs. They ran the first run with a set of aftermarket wheels, the 2nd run with a set of stock factory wheels and the 3rd run with a set of HRE P45S wheels, all in 20” sizes.

These results highlight the effects of rotational inertia on drive-train losses (the hp lost between the engine crank and the ground). Wheels and tires contribute to drive-train losses as energy is used to spin up the wheels (and decelerate the wheels under braking). From the dyno chart you can see the effect of replacing factory wheels with lighter HRE wheels and see the negative effects of installing heavier aftermarket wheels.

Results:
1. (Blue curve) Factory wheels: 20”x9.0” with Pirelli 275/40-20 tires weighing 68 lbs combined per rear wheel. – Max hp: 371 hp, Max Torque: 375 ftlbs - (Baseline)
2. (Red curve) Aftermarket wheels: 20”x9.0” with Pirelli 275/40-20 tires weighing 72 lbs combined per rear wheel – Max hp: 369 hp, Max Torque: 373 ftlbs - (A [-] loss of 2 hp and 2 ftlbs)
3. (Green curve) HRE wheels: 20”x11.0” with Nitto 315/35-20 tires weighing 60 lbs combined per rear wheel – Max hp: 380hp, Max Torque: 384 ftlbs - (A [+] gain of 8 hp and 9 ftlbs and that is running a 2” wider wheel/tire combo)

Conclusion:
The engine obviously still cranks out the same amount of hp and torque, the lighter HREs simply waste less of it before it gets to the ground. Also interesting to note is that the gains are not just peak gains, but gains across the entire rev range. If they had done a braking test, we would have seen similar results as the rotational inertia effects also have a significant effect on how much energy is used to stop the wheel/tire combo vs. stopping the car. We talk about these effects all the time and focus on designing lightweight wheels with low rotational inertia, but it isn’t every day that you get to see real hard data showing the true effects.

[Silver-SS]

Nice thanks!

[hawk02]

I think we all knew lighter wheels improve performance. This just confirms it with some real numbers.

[SPCBA]

Pretty much a give in that lighter wheels increase performance. Any where you can reduce rotional mass is a good thing. Great write up thanks for sharing it.

[Ajmalian]

Originally Posted by SIMSS

I came across this article and wanted to ask what your thoughts are? Great that it's done on a Camaro SS.

Article with dyno graph came from http://teamspeed.com/forums/aventado...orsepower.html

Test:
Davenport Motorsports (Custom Performance Parts and Service : Davenport Motorsports) of Canada, wanted to see the dyno effects of running different wheels on cars. They took a factory 2012 Camaro SS and ran 3 dyno runs. They ran the first run with a set of aftermarket wheels, the 2nd run with a set of stock factory wheels and the 3rd run with a set of HRE P45S wheels, all in 20” sizes.

These results highlight the effects of rotational inertia on drive-train losses (the hp lost between the engine crank and the ground). Wheels and tires contribute to drive-train losses as energy is used to spin up the wheels (and decelerate the wheels under braking). From the dyno chart you can see the effect of replacing factory wheels with lighter HRE wheels and see the negative effects of installing heavier aftermarket wheels.

Results:
1. (Blue curve) Factory wheels: 20”x9.0” with Pirelli 275/40-20 tires weighing 68 lbs combined per rear wheel. – Max hp: 371 hp, Max Torque: 375 ftlbs - (Baseline)
2. (Red curve) Aftermarket wheels: 20”x9.0” with Pirelli 275/40-20 tires weighing 72 lbs combined per rear wheel – Max hp: 369 hp, Max Torque: 373 ftlbs - (A [-] loss of 2 hp and 2 ftlbs)
3. (Green curve) HRE wheels: 20”x11.0” with Nitto 315/35-20 tires weighing 60 lbs combined per rear wheel – Max hp: 380hp, Max Torque: 384 ftlbs - (A [+] gain of 8 hp and 9 ftlbs and that is running a 2” wider wheel/tire combo)

Conclusion:
The engine obviously still cranks out the same amount of hp and torque, the lighter HREs simply waste less of it before it gets to the ground. Also interesting to note is that the gains are not just peak gains, but gains across the entire rev range. If they had done a braking test, we would have seen similar results as the rotational inertia effects also have a significant effect on how much energy is used to stop the wheel/tire combo vs. stopping the car. We talk about these effects all the time and focus on designing lightweight wheels with low rotational inertia, but it isn’t every day that you get to see real hard data showing the true effects.

All sounds well and good with your research, however I do have one more little query which has a lot to do with your research. Besides the increase and decrease in weight, does diameter of the rim affect dyno figures? I mean if I was to put 22" or 24" rims,I understand I am adding weight so yes technically I should be losing HPs...but what if I had slapped on light weight 22" wheels, ones that equate to be the same or lighter than 20" wheels with tires mounted on in both cases, then what would the results be on the dyno? What do you reckon?

[LSxJunkie]

Originally Posted by Ajmalian

All sounds well and good with your research, however I do have one more little query which has a lot to do with your research. Besides the increase and decrease in weight, does diameter of the rim affect dyno figures? I mean if I was to put 22" or 24" rims,I understand I am adding weight so yes technically I should be losing HPs...but what if I had slapped on light weight 22" wheels, ones that equate to be the same or lighter than 20" wheels with tires mounted on in both cases, then what would the results be on the dyno? What do you reckon?

Physics. If your 22s weigh the same as 20s, but the weight is concentrated farther away from the axis, it takes more torque to turn them. If they weigh less, it could take the same or less power to turn them.

It takes more power to swing a 4 foot pole with a 10 lbs weight on the end than it does to swing a 6 foot pole with a 10lbs weight on the end.

[willhe64]

But is the gain enough to warrant the expense of lightweight forged wheels?
For me that is a no.

[SPCBA]

Originally Posted by willhe64

But is the gain enough to warrant the expense of lightweight forged wheels?
For me that is a no.

It is not only a gain in Hp bit acceleration, braking, cornering. I think changing the diameter also changes the ratios.

[nitto85]

Originally Posted by willhe64

But is the gain enough to warrant the expense of lightweight forged wheels?
For me that is a no.

This is my answer as well.

[AKA-22]

to those gains and losses its not worth spending 1000 more on a set of wheels.....

[KMPrenger]

Originally Posted by AKA-22

to those gains and losses its not worth spending 1000 more on a set of wheels.....

Agree, but it is a nice bonus when you are already looking to change wheels and tires like I may be doing at some point before summer next year (well, rims first...tires later on). I'm looking at some Factory Reproductions ZL1 wheels that are said to be a tad lighter than the stock RS/SS wheels and won't be that expensive. By the time I re-sell my stock wheels, it won't be that expensive of a change for rims. Then if I go with a tire like the General Tire Gmax tires, which weight a couple lbs less per tire in the front, and 6 lbs less than each in the rear, thats some decent rotational mass shaved.

So that coule be 8 or so lbs lost in each rear tire which could be an extra 5 - 10 HP gained. Sure its not much, but I'll take it lol.

[AKA-22]

solution.. take your spare out of trunk!

[Norm Peterson]

You can take the spare out either way you go.

The point is well taken that the benefit may not be worth the cost to anybody who isn't running in any sort of precisely-timed competition.

But if you need to drop another 0.100 - 0.200 seconds at autocross or 0.050 second at the dragstrip, here is one place you'll find it for about a 5 lb difference per corner (x 4).


Norm

[SPCBA]

Originally Posted by AKA-22

solution.. take your spare out of trunk!

While taking weight out can be effective, there is a huge difference in normal weight and unsprung or rotational weight.