unsprung weight( weight from below the suspension point) is equal to saving about 3.85 to 1 vs sprung weight... in other words, if u saved 10 pounds of unsprung weight, it would be the equivalent to saving 38.5 pounds of interior, CF parts etc. so yes rim weight is a major factor on performance and i suppose gas mileage...

 

rpf1s are the best rims for the price in my opinion. one of the best upgrades ive done..

 

It's just physical fact.

Moment of inertia for a basic cylindrical object is:

I = mr^2

This is a simplified representation, since the the tire and wheel are of different densities and the space between the tire and wheel is hollow; not to mention the geometry of the wheel, but it describes the the phenomena properly if we take the total weight and pretend its distributed evenly across its volume.

Since the total radius of the wheel/tire combo is identical; the only changing value is mass, m. If m increases, I increases. I is the mass moment of intertia, or the resistance to rotation about our specified axis (the one that passes through the face of the wheel).

Since the r value remains constant, doubling the mass, doubles I. Whether the user "feels" a difference or not, there is a very real and measurable difference.

The wheel also rotates about another axis as well during cambering. The equation for that axis is more complex, but has the value m in it as well.

Theres also linear momentum as the wheel/tire undergoes suspension travel. Linear momentum is simply:

P = mv

When the tire/wheel encounters a disturbance in the road that causes it to move up to avoid it, or down to meet it, it accelerates and gains velocity. A higher mass equates to higher P, which means the wheel/tire will have a higher tendency to keep going in that direction even after having already rolled past the disturbance. Lower mass means the wheel/tire will return to it's original position sooner and with less effort from the suspension.

 

Got mine today

 

Again....I'm asking if it's WORTH IT over the 928M impeller for the Vortech. I know it'll make you quicker...it's a fact and I never thought otherwise. What I was wondering is how much quicker it would make you. From reading the articles posted, I'm really not impressed at all.

 

Where did you get these figures?

 

Here's the only test I could find, but I know I've seen a import mag test this and it was a little more pronounced.

http://www.carcraft.com/projectbuild...son/index.html

 

Looked it up a little while back before I ordered my rims. Google unsprung weight vs sprung weight ratio.

 

Are you getting different answers than you did in August?

https://my350z.com/forum/wheels-and-...ower-size.html

 

man, when i saw this thread title i just new it be you lol, why dont you cough up some dough and get some volks or nismo rims that are 19 and that are under 20lbs. I know they make them so start saving because if i were in your position i would go that route.

 

I wouldn't say you have to be on the lightest wheel on the market, within 2-4 lbs the difference is minimal (as seen here, http://www.modified.com/tech/modp-09...st/5zigen.html) but when your talking 5-10 lbs per wheel you start to get in the differences you can feel. Try and keep it close to 20-23 lbs per wheel depending on budget maybe a little more.

 

make more power and rock what you got.

What are you trying to race that has you this concerned how fast you are? pink slips involved?

I'd probably get the 3.9 final drive 1st if you are interested in better acceleration.

 

Spending the money isn't the problem. It's spending it just to get a marginal gain...if any. That's what makes this so hard for me.


LOL...I raced a Camaro the other day ( he put down 396whp naturally aspirated ) and he pulled half a car on me. This is the car I've been gauging my car agaist as he's been the closest race I've had in a while.

With the 3.9 I'm worried more about fuel economy than anything else....although it does sound tempting.

What about impeller vs. 3.9 or 4.1?

 

I actually noticed a difference going from my stock 18's to 19" LMGT4's. Hard to say what exactly the difference was, though.

 

I say Hp's over gearing but that's coming from a motor guy...

 

Yeah....looks like I'm keeping my 20's. I just can't find enough info to make me think getting lighter wheels will make me that much faster.

 

The Obama administration begs to differ.

"Mr. Cole explained that to do this you would need a trunk FULL of batteries and a LNG tank as big as
a car to make that happen and that there were problems related to the laws of physics that prevented them from...

The Obama representative interrupted and said (and I am quoting here) "These Laws of Physics? Whose rules are those?? We need to change that. (Some of the other Obama folks actually wrote down the law's name so they could look it up.) We have the Congress and the Administration. We can repeal that law, amend it, or use an executive order to get rid of that problem.

That's why we are here, to fix these sort of issues".

 

Fact check;

http://www.factcheck.org/2009/06/oba...ws-of-physics/

 

I went from 29lb wheels to 24 lb wheels to 20lb wheels .. felt a difference with each jump.

in comparison, with each mod I did (plenum spacer, intake, dual exhaust, berk hfc's, osiris tune) I couldn't really feel a difference.

I am sold on light weight wheels being one of the best things you can do for overall performance 'feel'

 

I felt a big diff between 20 in and 18 in rims in accel