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    • The effect of wheel weight and rotational mass on power - Dyno testing three sets of 20 inch wheels

      There is a reason car companies spend big money on exotic materials in order to reduce weight. Ford includes carbon fiber wheels on the Mustang GT350R because reducing rotational mass has quite an effect on performance.


      The test below is an old one done by Davenport Motorsports but the physics remain true as ever.

      They dyno tested a 2012 Camaro SS with three sets of 20 inch wheels.

      1. (Blue curve) Factory wheels: 20x9.0 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: 20x9.0 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: 20x11.0 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)


      The 12 pound difference between the lightest and heaviest set of wheels and tires is worth almost 11 wheel horsepower on the dyno despite the lighter wheel and tire combo also being wider.

      Now, you are not making more power with lighter wheels and tires and the engine still has the same output. You are reducing losses though in that power getting to the ground. In other words, improving efficiency.

      Remember the roadcouse test last year showing the lap time difference between standard and carbon fiber wheels on a Porsche 991.1 Carrera S? Well, now can see how the weight difference also plays out on the dyno.

      This article was originally published in forum thread: The effect of wheel weight and rotational mass on power - Dyno testing three sets of 20 inch wheels started by Sticky View original post
      Comments 8 Comments
      1. richpike's Avatar
        richpike -
        Also helps braking and handling.

        -Rich
      1. Batman's Avatar
        Batman -
        The question is if it's worth the price of admission for what you're getting. The 911 carbon wheels cost about $20K. So basically, you're spending about $20K to gain about 11whp. And God forbid you hit the curb or a pot hole. It reminds me of CCBs. At the track, people swap them out for steel units because of the cost of replacement.
      1. CobraMarty's Avatar
        CobraMarty -
        Or is the difference in 'power' due to the rotational weight difference because of the way the DynoJet dyno works.

        Would the power/dyno results be the same on a Mustang dyno?
        The engine is not making any more power with the lighter wheels.
      1. PianoProdigy's Avatar
        PianoProdigy -
        I tested something similar 13 years ago.

        https://www.corvetteforum.com/forums...-the-dyno.htmlp
      1. Sticky's Avatar
        Sticky -
        Click here to enlarge Originally Posted by PianoProdigy Click here to enlarge
        I tested something similar 13 years ago.

        https://www.corvetteforum.com/forums...-the-dyno.htmlp
        That's a great post! The graphs are gone though?
      1. Sticky's Avatar
        Sticky -
        Click here to enlarge Originally Posted by CobraMarty Click here to enlarge
        Would the power/dyno results be the same on a Mustang dyno?
        The engine is not making any more power with the lighter wheels.
        I don't see why the Mustang wouldn't show gains but the gains would not be the same due to how it reads.

        GPS in theory should show some minor gains too depending on how long you go.

        We saw the difference in a laptime already but look at how long that lap needed to be.
      1. PianoProdigy's Avatar
        PianoProdigy -
        Hmm, yeah I just noticed that. Maybe I’ll plugin my old hard drive backup and see if they are on there.
      1. Sticky's Avatar
        Sticky -
        Click here to enlarge Originally Posted by PianoProdigy Click here to enlarge
        Hmm, yeah I just noticed that. Maybe I’ll plugin my old hard drive backup and see if they are on there.
        I know that's a bunch of work but would awesome to add in.