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    • HPF compares the effect of different sized wheels on the dyno

      Well all know lighter wheels are a good thing. But just how big is the difference? Well, as a car makes more power the effect is easier to see. HPF took a Stage 4 and tested it with a wide set of 19's and then the stock 19 inch M3 wheels. The effect is magnified on a more powerful car and at one point in the graph there is an over 60 whp difference between the heavier wheels and the skinnier, lighter stock wheels. Check out the vid on the next page.

      This article was originally published in forum thread: HPF compares the effect of different sized wheels on the dyno started by Sticky View original post
      Comments 35 Comments
      1. Sticky's Avatar
        Sticky -
        Video:

      1. 1cleanAMG's Avatar
        1cleanAMG -
        I have always found big wheels with flush setups just plain stupid if you are looking for performance.
      1. Sticky's Avatar
        Sticky -
        Click here to enlarge Originally Posted by FR305 Click here to enlarge
        I have always found big wheels with flush setups just plain stupid if you are looking for performance.
        Well, he kind of needs them for traction.
      1. 1cleanAMG's Avatar
        1cleanAMG -
        Click here to enlarge Originally Posted by Sticky Click here to enlarge
        Well, he kind of needs them for traction.
        Not really. He could have more of a Full setup with a 18 wheel just as wide as the 20's but with a larger tire wall.

        for example:

        Click here to enlarge
      1. Sticky's Avatar
        Sticky -
        Click here to enlarge Originally Posted by FR305 Click here to enlarge
        Not really. He could have more of a Full setup with a 18 wheel just as wide as the 20's but with a larger tire wall.

        for example:

        http://ll.speedhunters.com/u/f/eagam...2/IMG_4551.JPG
        Oh, you mean same width but just not a "bling" ?

        They are 19's.
      1. 1cleanAMG's Avatar
        1cleanAMG -
        Click here to enlarge Originally Posted by Sticky Click here to enlarge
        Oh, you mean same width but just not a "bling" ?
        Exactly. Bling = Weight

        Click here to enlarge Originally Posted by Sticky Click here to enlarge
        They are 19's.
        He should have 17's Classic CCW's
      1. LostMarine's Avatar
        LostMarine -
        $#@!.. im wanna put the 17's on now more than ever!!
      1. M3_WC's Avatar
        M3_WC -
        European Car put wider wheels and more rubber on their Project Z4M. They got 13whp/10 ft.lbs gain over the OE wheel and tire set-up. The 18x10 Forgelines with upsized tires were 4 lbs lighter.
      1. Sticky's Avatar
        Sticky -
        Click here to enlarge Originally Posted by FR305 Click here to enlarge
        He should have 17's Classic CCW's
        Perhaps, but he can also have more than one set of wheels. One for looks, one for the track.
      1. 1cleanAMG's Avatar
        1cleanAMG -
        This is how you do it right

        CCW Classics matte black centers with gloss black lips.

        Click here to enlarge

        Click here to enlarge
      1. M3_WC's Avatar
        M3_WC -
        Click here to enlarge Originally Posted by Sticky Click here to enlarge
        Perhaps, but he can also have more than one set of wheels. One for looks, one for the track.
        European Car kind of had opposite findings. Their upped tire size and wider wheels, gained HP/TQ.

        They attributed the gains to the lighter weight, not rolling diameter.
      1. Sticky's Avatar
        Sticky -
        Ya, I guess, I know I will be running wheels for looks on the street and wheels for performance on the track.
      1. Sticky's Avatar
        Sticky -
        Click here to enlarge Originally Posted by M3_WC Click here to enlarge
        European Car kind of had opposite findings. Their upped tire size and wider wheels, gained HP/TQ.

        They attributed the gains to the lighter weight, not rolling diameter.
        It is about the weight more than anything.

        The wheels here in the vid are both 19's.
      1. M3_WC's Avatar
        M3_WC -
        Click here to enlarge Originally Posted by Sticky Click here to enlarge
        It is about the weight more than anything.

        The wheels here in the vid are both 19's.
        He says the ratio between the tire diameter and roller diameter change, that is what caused the difference in power readings. He is not really attributing it to weight, but rather the different rolling diameters.
      1. Sticky's Avatar
        Sticky -
        Click here to enlarge Originally Posted by M3_WC Click here to enlarge
        He says the ratio between the tire diameter and roller diameter change, that is what caused the difference in power readings. He is not really attributing it to weight, but rather the different rolling diameters.
        That is true as well but the weight also is a factor.
      1. M3_WC's Avatar
        M3_WC -
        Click here to enlarge Originally Posted by Sticky Click here to enlarge
        That is true as well but the weight also is a factor.
        Yeah I agree. I think it is the bigger factor actually.

        Here is some data from Europeancar's Project Z4M. They find the less rotational mass attributes to the bulk of the gains. As HPF seems to think the tire diameter is the main factor.
        http://blog.forgeline.com/tag/project-z4m/
      1. mazdaspeed6's Avatar
        mazdaspeed6 -
        Click here to enlarge Originally Posted by LostMarine Click here to enlarge
        $#@!.. im wanna put the 17's on now more than ever!!
        k1's ftw
      1. BASELINE's Avatar
        BASELINE -
        The rolling diameter is effectively changing the gearing and in this case making it taller, so the torque multiplication factor decreases with the bigger tire/wheel combo, and the weight is also a huge factor. This is a really cool video, though....I love it when shops test different things that we always talk about and put some hard numbers on them.

        I wonder if the difference is as great because the car here is making such big numbers. If it was a car making 400ish whp, the difference might have been much smaller.
      1. GG///M3's Avatar
        GG///M3 -
        Click here to enlarge Originally Posted by FR305 Click here to enlarge
        Not really. He could have more of a Full setup with a 18 wheel just as wide as the 20's but with a larger tire wall.

        for example:

        http://www.bimmerboost.com/images/im...10/12/1585.jpg

        Great point. I'm thinking about going with 16's when I go to the track this coming spring. The taller side wall helps a good bit. I wonder what the tq difference was with the tire/rim swap?
      1. mazdaspeed6's Avatar
        mazdaspeed6 -
        tires are pretty heavy too, i wonder what the difference would be from a 305-45-18 to a 305-30-20 would be...