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Originally Posted by chmercer
and the rear 18x12 with 275 tire weighs less than stock 350z 17s with 225s so unsprung weight, while people like to bitch about it with calculator and physics book in hand, in reality is not really an issue. maybe if you want to set records then yeah whatever but if that was the case you need a new platform.
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Regardless of what you have to tell yourself, unsprung weight is unsprung weight and comparing your combo to a heavy stock combo is lame. My 245/40R17 combined with 17x9 +15 TE37 weighs all of 44 pounds. My new front setup, arriving from Japan sometime in the next 46-76 days, will weigh one to two pounds less per wheel. You, on the other hand, had a tire that was two pounds heavier and farther from the hub. You also had a wheel with a huge barrel farther from the hub. Your center may have been light but the barrel was heavy as hell. How much did those wheels weigh? I know the Meister S2R in 18x9 was 22.3lbs. Let's say yours was extraordinarily light and weighed the same. 22.3 plus 29 equals 51.3lbs. That's 8.3lbs heavier than my setup, per wheel. That's hardly inconsequential.
Oh my God, I might have used a calculator (I didn't) to determine that. It must mean nothing!
It has been my experience, and I doubt I am the exception to the norm, that lighter wheels increase turn-in and suspension efficiency. I've had to dial back toe because turn-in was increased such a large extent.
nIsmo400r, do you find it necessary to run 18s? 17s are lighter, cheaper, and have less circumference in the barrel to better centralize rotating mass and decrease turn-in time, decrease braking distances, and decrease acceleration times.
This whole track bit is about getting faster, mostly through the improvement of your driving skills but also by upgrading the car to work more efficiently. Why not make it the absolute easiest on yourself and buy the lightest wheels that still fulfill your needs?
Oh, and don't forget that a wider wheel with a lower offset increases the leverage ratio of the suspension, possibly requiring an increase in spring rate to compensate.