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Originally Posted by Lynxis
On the OEM tires, I could hit a top speed of 167kph before needing to brake and on 225/45r17 Hankook RS3s, my top speed is 166kph by speedo. Also factor in the 1.02 increase in tire diameter with the 225 over OEM 215 and that speed is... 169kph.
So my top speed is actually higher? Yes. With a caveat that I can enter the straight at 55kph on OEM tires and and 60kph (61kph corrected for taller tire) on the RS3s.
So, the total acceleration on OEM tire is 112kph over the same distance. On my RS3s, it's 108 (corrected for taller tire)
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You can't just go by speed differential because acceleration drops dramatically with more speed. It would be more appropriate to go by energy added down the straight. Energy is a function of speed squared (1/2 mass * v^2).
OEM tires: 166^2 - 55^2 = 24,531
RS3 tires: 169^2 - 61^2 = 24,840
Not really any difference in energy added down the straight.
Rolling resistance is a very small factor even for a lowish hp car.
Quote:
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The reality is that the difference in resistance is so low compared to the power the wheels are trying to put down that you'd need a runway worth of distance for it to matter
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Exactly!