[HRE_Mickey]

Test:
Davenport Motorsports (www.davenportmotorsports.com) 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.


Dyno Run - Effects of wheel/tire weights on wheel horsepower by HRE Wheels, on Flickr

[RobertRO]

Very interesting, thanks for posting this.

[UltraRacer13]

great post!

[O-cha]

I still don't get why people don't already know this, this is well known to anyone "in the business". Where the weight is in the wheel is also important, same overall weight but more weight on the barrel itself would make a bigger impact.

The snapshot it also somewhat misleading as most dynos are done at high speed, in higher (lower number) gears it makes less of a difference.

The same thing happens with lightweight flywheels.

[HRE_Mickey]

Originally Posted by O-cha

I still don't get why people don't already know this, this is well known to anyone "in the business". Where the weight is in the wheel is also important, same overall weight but more weight on the barrel itself would make a bigger impact.

The snapshot it also somewhat misleading as most dynos are done at high speed, in higher (lower number) gears it makes less of a difference.

The same thing happens with lightweight flywheels.

People know, but they often need to be reminded.

If you look at the dyno plot, you will see more area in the power curve, not just the peak. So there's more translated power at all RPM ranges.

[HRE_Mickey]

Great info.

[signes]

It would have been interesting to see for the 3rd run with HRE wheels the same tires being used. Wider section width (and tread compound, wear, etc.) will impact the results.

[HRE_Mickey]

In this case, the 3rd scenario is using wider tires.

[M3_WC]

Originally Posted by O-cha

I still don't get why people don't already know this, this is well known to anyone "in the business". Where the weight is in the wheel is also important, same overall weight but more weight on the barrel itself would make a bigger impact.

The snapshot it also somewhat misleading as most dynos are done at high speed, in higher (lower number) gears it makes less of a difference.

The same thing happens with lightweight flywheels.

Exactly.

[M3_WC]

European Car Magazine did these tests a while back with their project Z4M, stock vs Forgeline wheels.

[HRE_Mickey]

I would say a lot of the average consumer does not know this. Or they don't care.

I see many people purchasing wheels that actually decrease the performance of their vehicle. Especially with some of the 3pc concave designs.

[hellrotm]

Originally Posted by Lon@HRE

I would say a lot of the average consumer does not know this. Or they don't care.

I see many people purchasing wheels that actually decrease the performance of their vehicle. Especially with some of the 3pc concave designs.

+1

It is sad to see people spend their hard earned money with some of these pathetic wheel companies.

[Inspired]

Was the dyno done on same day? There are a lot of conditions to factor before coming to a conclusion that a specific aftermarket wheel will actually lose HP.

[signes]

Originally Posted by Lon@HRE

In this case, the 3rd scenario is using wider tires.

Exactly the point, that doesn't make it a consistent test - it isn't just isolating wheel/tire weight, Another variable is changing for your third run (tire width, tread, compound, etc.)

[ragingpanda]

Wow I was expecting more power out of a stock 2012 Camaro SS...