I responded to thread at another forum after doing some quick research (a poster asked if there was any documentation on the effects of unsprung weight)... I had read untold articles on it, so when I did a google to find something quick, I came up with the following...

Lower weight = higher performance. At what point does weight become important? The relationship is linear, meaning 1 lb is certainly not helping performance, 5 is 5x worse, and 10 is 10x...

Here's the simple wiki on it:
http://en.wikipedia.org/wiki/Unsprung_weight

http://www.bluegooseriders.org/riders/roadracing.html
This is a Biker's site, but the theories are sound.

Weight is directly related to horsepower. It is estimated that every seven pounds you eliminate, gains one horsepower.
There are many benefits to reducing unsprung weight. One of the most noted is that, 1 kg of reduction in unsprung weight is approximately equal to 6kg reduction in sprung weight.

One easy way to reduce unsprung weight is the use of lighter weight wheels. By reducing the weight of the wheels, you also reduce the gyroscopic effect. The gyroscopic effect is the force that is generated from a spinning object. To get an idea of what this is, hold a bicycle tire in your hands and spin it. Now try and change the direction of the wheel. You will notice it is hard to do especially if the wheel is heavy. By reducing weight in the wheels you will reduce this effect resulting in better handling during cornering and improved acceleration. Magnesium wheels are the choice for most Superbike racers, and some are even going to carbon fiber but these are very expensive and typically not as durable as cast aluminum.
+ + +

So, if you can remove 70 lbs from your car, it's like adding 10 hp. Better yet, if you remove 20 lbs of unsprung weight (say 5 per wheel), that's like removing 120 lbs of weight, which is like adding 17 hp.

This is why performance minded racers and drivers are constantly seeking ways to reduce not only weight but more importantly unsprung weight. I'm chasing 2-piece rotors like the PFC ones currently made for the base 997. I'm on a notification list from PFC for when they start making rotors for the 997S because they should be about 4 lbs lighter per wheel. One of the reasons I stuck with Pilot Sport Cups is they are the lightest R-comp out there at 25 lbs each (vs. upwards of 30 for something from Toyo / Nitto). Same with wheels - light weight 18s at say 20 vs. others at 25 or 30 lbs.

I'm just saying - don't underestimate the impact of weight all around. Tires, wheels, rotors, stuff in the trunk (some guys snicker when they see me taking everything out of my car at the track - the tool kit, compressor, maps, etc.). It all goes in my track box and probably weighs 50 lbs, equivalent to 7 more hp.

 

I'm with you on this one... That's why my first mod was BBS wheels. If you wouldn't mind, please let me know when you get notified by PFC - I am interested in those brakes as well.

In fact, I think I pointed you to them on Rennlist... LOL

 

Good write up thanks! One of the reasons I went with the lobster fork wheels.

 

Love forum trolls who don't understand the concept.

"You can't add 10hp by having light wheels, you have to do motor work..." etc.

Then they turn around and ADD weight with the chrome hoops and the full-surround sub boxes and neon and ...