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Originally Posted by Captain Insano
Wouldn't overall vehicle and rotating weight play a large role in the propsed test, not just drag? If the wheels had a decent amount of weight difference, I woudl think even over 1 lb per wheel/tire, that might be affecting the overall time it takes vehicle to slow down during the test. So I'm saying you have at least two variables at play in this test. And really more, wind speed changes that occur in real life, even just from minute to minute. Things like that.
Not saying it's a bad idea, just pointing out you might not be 100% confident any one thing you are trying to measure (drag) is all that is affecing the car during the proposed test.
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This is correct, although my assumption is that the moment of inertia of the replacement wheels is close to that of the stock wheel and any difference would be negligible when compared to the inertia of the vehicle. Of course it won't be perfect, but engineering is all about making assumptions. A quick calculation of the energy stored due to the linear velocity of the vehicle and the energy stored due to the rotational velocity of the wheels (and any other rotating components if you would like) should show this assumption to be quite good for any reasonable wheel choice.
Quote:
Originally Posted by EarlQHan
To be honest, I think you guys are overthinking a very simple matter. These are low-powered, production-based, closed-wheel cars. The aero effect is more than likely negligible for a 7.5" wide wheel vs. a 9" wide wheel. The tire is the important part, and assuming you make a similar increase in tire width, the additional grip will overcome the drag and inertial forces in lap times. And that's the thing that really matters here; sometimes it's really easy to lose sight of that.
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I would agree, except I believe @
CSG Mike has mentioned in the track forums that he thinks a stock powered car is faster around a track on 8" wheels than 9" wheels.
Quote:
Originally Posted by EarlQHan
Edit: Simplest solution I can think of is stretching the OEM tire on a wider wheel. Some wheels, like the RPF-1 might be as light as stock, making the weight similar. I imagine the inertia isn't too different. Do a coast down with each. Not exact, but it can be used as a reference if you want to know how a wider wheel alone will affect the car.
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This is a great idea, and made me think of a similar idea. Just compare the stock wheels/tires to the stock wheels/tires with a large spacer. I don't know how large of a spacer could safely be used (even if temporarily for this test), but this would eliminate a few key variables.
Quote:
Originally Posted by infinite012
Oh herro prease
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I hope my responses don't sound argumentative. You all made very good points. I think peer review is very important, and this forum is great for that.
