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      07-07-2008, 02:07 PM   #26
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Originally Posted by Mickb View Post
I don't have this problem. I understand full well that if the bigger rim size is accompanied by additional weight, or the distribution of the weight of the rim is more unfavourable then there is a performance penalty, in much the same way as any weight increase in the car. The difference in unsprung weight is amplified due to the rotation factors other have alluded to above.
When I was saying I can't work it out I meant when both versions 18" and 19" weight almost the exact same. Now if the weight is greatly increased with the 19" then I could understand it more.

Originally Posted by Mickb View Post
I seem to remember a discussion paper (of either Porsche or Honda) on the effect of PCCB's where they approximated that a reduction in unsprung weight was the equivalent of a 4x reduction in sprung weight. i.e. lets say ceramic rotors saved you 5lbs per corner this would be the equivalent of taking out 20lbs from the car (eg seats or exhaust). This is obviously weight reduction for dummies and doesnt take into account weight distribution etc
I think this is a misunderstanding of what is meant by this 4 times sprung weight, I believe it's the improvement in direction changes and steering feel they are talking about instead of improvements in actual performance.

Might be wrong but it's how I understand it to be.

Originally Posted by Mickb View Post
All I would argue is that the difference between the OEM 18's and 19's is insignificant in this regard and I bet if you put a vbox on the same car and tested 0-60's etc you wouldnt even get .1 of a difference in the outcome.

That's basically the same as I posted some time ago, I think when measured the improvement will be in 0.00?.

The only real reason for picking one over the other is personal preferrence.