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Rotational Weight isn't my concept. It's a basic concept of car design which is particularly important in performance cars and in motorsports. It's entirely based in physics where it's called Rotational Inertia or Moment of Inertia
I'm sure everyone already understands the important of weight reduction to performance. Most people also have heard of "unsprung" vs "sprung" weight. The basic theory of that is that you aim to reduce as much unsprung weight as possible. So much so is the importance of this, that it is beneficial to reduce your unsprung weight, even if you then need to add additional sprung weight to meet a minimum weight requirement in motorsports.
But there is also rotational weight. Rotational weight can be both sprung (crankshaft, gears, drive shafts etc), and also unsprung, wheels, brake rotors etc. Chad Knaus said in a recent "NASCAR Performance" show that in order of important is rotational weight (most), unsprung and then sprung (least). The reason reduction of rotational mass is most important is that the engine must accelerate its mass PLUS overcome its rotational inertia.
Doing a google search brought up articles specifically on this topic in relation to motorsports:
Auto Racing
So reduction of the rim size reduces the weight and thus the rotational inertia.
I also don't think you should immediately discount "handling" as a requirement for straight line acceleration... but that's harder to quantify, although we already know that even on a GTI, the 17" wheels have beat out the 18" wheels around a track...
Edit: Oh, and team_v got in whilst I was writing that up. Cheers mate... it's good to find a 2nd person who knows what I'm talking about
I'm sure everyone already understands the important of weight reduction to performance. Most people also have heard of "unsprung" vs "sprung" weight. The basic theory of that is that you aim to reduce as much unsprung weight as possible. So much so is the importance of this, that it is beneficial to reduce your unsprung weight, even if you then need to add additional sprung weight to meet a minimum weight requirement in motorsports.
But there is also rotational weight. Rotational weight can be both sprung (crankshaft, gears, drive shafts etc), and also unsprung, wheels, brake rotors etc. Chad Knaus said in a recent "NASCAR Performance" show that in order of important is rotational weight (most), unsprung and then sprung (least). The reason reduction of rotational mass is most important is that the engine must accelerate its mass PLUS overcome its rotational inertia.
Doing a google search brought up articles specifically on this topic in relation to motorsports:
Auto Racing
In many cases, car handling can be improved by increasing the diameter of your car's wheels matched with a lower aspect ratio tire. The drawback of this is that most plus sized wheel and tire combinations are heavier than the stock smaller wheel size with a taller tire sidewall. This can make for slower 0-60mph and 1/4 mile times.
I also don't think you should immediately discount "handling" as a requirement for straight line acceleration... but that's harder to quantify, although we already know that even on a GTI, the 17" wheels have beat out the 18" wheels around a track...
Edit: Oh, and team_v got in whilst I was writing that up. Cheers mate... it's good to find a 2nd person who knows what I'm talking about
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