will I notice a difference?

[CSG Mike]

Originally Posted by stugray

Oh! So you have done the experiment! Cool.

However you are right.
Shedding 10.8 lbs from the wheels versus shedding > 15 lbs from the trunk are NOT the same.
Removing the spare will make a BIGGER difference.

However I still contend that the driver will not FEEL a difference under either option (hence why I said to do the experiment).

Now - will an experienced driver, on a track, with a datalogger be able to detect the difference between stock rims and rims that weigh 2.7 lbs lighter (using the data)?
Maybe.

How about this experiment: Could a driver (on the street) be able to tell the difference in handing from a set of tires with 20,000 miles on them versus 40,000 miles?
Because that is probably the difference of ~3 lbs per wheel in lost tread....

You'll know the first time you step on the gas while next to another FRS....

[8R6]

driving/racing lessons will make more difference than any weight loss for a street car

[stugray]

Originally Posted by CSG Mike

You'll know the first time you step on the gas while next to another FRS....

We are talking about 10 pounds!

So all of you with calibrated butt dynos must be able to tell if you just took a shit or not...

So you guys are saying that you can tell the difference between a full tank of gas, and a tank with only 11 gallons in it just by driving the car.

NIIIICEEEE !!!

Just save the cash and drive around with only half a tank.
Thats a difference of 40 lbs!

[CSG Mike]

Originally Posted by stugray

We are talking about 10 pounds!

So all of you with calibrated butt dynos must be able to tell if you just took a shit or not...

So you guys are saying that you can tell the difference between a full tank of gas, and a tank with only 11 gallons in it just by driving the car.

NIIIICEEEE !!!

Just save the cash and drive around with only half a tank.
Thats a difference of 40 lbs!

I'm saying if you were next to a FRS with stock wheels, and you both stomp on the gas at the same time, you will noticeably pull. Lets make both cars automatics, just to eliminate the driver variable, and completely stock, except for the wheels on your car.

[CSG Mike]

Originally Posted by HRE

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.

Click this bar to view the full image.

From another board.

I wish the wheel widths and tires are the same, but even with more tire and rim, the lighter combo sees a gain.