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GTOholic
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Discussion Starter #1
I was told that switching from 17" to 18" wheels may have cost me a tick or two in the 1/4 mile. But because I went to a lower profile tire with a larger wheel, the overall diameter is actually LESS than stock... not to mention the new wheels and tires WEIGH less than stock.

So, logic tells me I should have GAINED a tick or two. Comments, anyone?
 

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FLORIT said:
I was told that switching from 17" to 18" wheels may have cost me a tick or two in the 1/4 mile. But because I went to a lower profile tire with a larger wheel, the overall diameter is actually LESS than stock... not to mention the new wheels and tires WEIGH less than stock.

So, logic tells me I should have GAINED a tick or two. Comments, anyone?
I am sure there are some engineers on the board that could shed more light on this, but I believe that you would have to know where the weight is located on the wheel/tire combo. The further out the weight is from the center of the wheel, the more it will affect the inertia.
 

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Feynman fan
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I'm not an engineer but... lively is correct. The geometry and mass are insufficient without knowing the relationship between the two. Let's say, for instance, that your new combo is lighter overall but that the weight is all concentrated at the rim and (shorter) tire whereas the stock combo had the weight more evenly distributed. In this case, the moment of inertia could well be greater for the new combo than for the stock one.
 

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Resident 10-second Priest
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FLORIT said:
So, logic tells me I should have GAINED a tick or two. Comments, anyone?
Well, we're gonna find out. I should pick up today my new set of 17-lb 17x8 OZ Superleggerra's with Nitto DRs on the rear. My 19x8 and 19x9.5 TSW's with Toyo Proxies have hooked up pretty well (1.7 60's on a non-brake stall launch). So I'm hoping the lighter rims and DRs and a partial-stall launch might net me a few tenths.

On my WRX, I went from stock 16" rims to lighter 17" rims and gained 2-tenths.

Padre
 

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I like boobs.
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Weight and diameter can go either way. Shorter sidewall with a lighter wheel will improve cornering and the lower unsprung weight helps regardless. Most aftermarket wheels that would be lighter than stock will have the weight distributed roughly the same as the stock wheel.
 
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