10-09-2015, 08:02 AM | #1 |
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Why do BMW Brochures Show lower milage with larger wheels
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10-09-2015, 08:03 AM | #2 | |
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10-09-2015, 09:45 AM | #4 | |
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10-10-2015, 09:37 AM | #5 |
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This.
More often than not, larger wheels increase unsprung weight and make the engine work a fraction harder which will reduce MPGs. If you notice the wheels on true race cars, they are often much smaller than a similar road car. The exception is when you select a lightweight tire and a lightweight wheel. Many times I have gone +1 and still reduced weight by 2-5lbs per corner. In those cases there is no negative.
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10-10-2015, 11:19 AM | #6 |
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It's not as simple as weight, although that's a big advantage...
Even if they weigh the same, or even if the larger wheel setup weighs slightly less, the larger wheel has a larger moment of inertia and will take more energy to accelerate and decelerate vs. the smaller one. http://hpwizard.com/rotational-inertia.html For performance, run the smallest wheels that will fit over your brakes. Might come at the expense of some turn-in feel, depending on the tire though, so that might be a motivator to keep the sidewall smaller.
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10-10-2015, 03:58 PM | #7 |
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This article may help understand why upsizing isn't best for fuel consumption, or always a performance benefit.
http://www.caranddriver.com/features...d-tires-tested Also wheel widths and tyre sections change on some wheel upgrades, so drag and rolling resistance can be changing as well. |
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10-12-2015, 08:31 AM | #9 |
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I ordered my 2014 S28i M Sport with 18" wheels for a very good reason.
When the run flats are gone, I'll buy Michelin PSS in 225/40R18 and 255/35R18 which will lower final gear about 4%. The car is already a low rpm monster, but acceleration will be better, and it'll feel lighter and get better gas mileage. Of course I have to recalibrate my Sanguage II down 4% or it'll look like I got way better mileage. Guys trying to keep miles off car wouldn't dream of this, but I barely drive the car. |
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