I was looking at some wheels that are 10lbs lighter then my stock 17s. Four of them would take off 40lbs off the wheels. With the same size tires how much quicker will my Z go?

 

It would be hard to quantify. Acceleration and braking will be better.

 

I'm speculating maybe at most 0.1 sec off your 1/4 mile ET and the trap speed might increase roughly 1 mph.

As for braking, you'll feel a small difference.

Lightweight rims help somewhat with performance, but defintely a very expensive mod to gains ratio.

 

Actually for every 100lbs you lose thats a tenth of a sec in the 1/4 mile.

 

You have to also factor in the rotational forces, its easier for the car to turn a light weight wheel than a heavy one. In addition, the inch size of the rims also play a role. It's a complicated physics equation that I feel asleep in high school and college, I wished I paid attention now .

In terms of acceleration, the 40lbs savings, probably helped in a very tiny way, but the size of the rim also plays a role. If you went from 17" to 18", there is an affect on acceleration. Sometimes going up higher 1" and lighter weight rims don't always translate to better acceleration, but you get better handling characteristics.

Best way to save yourself from the physics equations is to visit a dyno or track. If your expecting large gains in acceleration, it isn't likely.

 

I am going to have to learn physics anyways.

 

Remember the rotating lbs is taken off. Running a full tank of gas would make about .2sec slower in the 1/4. One gallon is about 5lbs. So 20gallons is a full tank. Having 1/4 tank is about 5gallons=25lbs. Meaning 75lbs would be roughly .1-.2sec off 1/4mile.

 

it'll help a lot. my sister replaced her aftermarket (heavy) 17" with 19" volks and she could tell the car was quicker. i put on heavy steelies with snow tires on my miata and the car is so slow now. stock 15" rims are 14.5 lbs + ~17 lb tires. the steelies combination probably weighed 5 to 10 lbs more.

 

Weight is crucial. I hate how sluggish my car feels with a heavy passenger. I don't even want jumper cables in my car because of the added weight.

 

they say 100lbs is good for .1sec

and they say 10lbs on a wheel is worth 100lbs anywhere else in regaurds to acceleration or braking...

now I wouldnt expect .4sec off. but I would say .2 is possible, .4 or more if you figure wider rubber with it.

handling will be improved on rough roads since the suspension can move more freely, the tire wont float over a bump.

 

I probably run in the mid 13s Without the spare,jack; 1/8gas .3 sec from the exhaust and wheels

 

I noticed a difference between my old 26lbs iForged FS-6s and my 18lbs 18" NISMOs. Acceleraction and breaking are a little more instantaneus. You will fell a difference, and especially on new sticky tires.

 

The question isn't how much the rim weighs, it is the inertia of the rim.

Example:

You have two rims that weigh 50lbs.

One rim has 95% of its weight located in the hub of the rim.

The other rim has 95% of its weight located in the ouside of the rim.

The first rim would yield HUGE.. i mean HUGE gains over the second rim.


It isn't how much weight, it is where the weight is.

To calculate performance gains, you would need a CAD drawing of the rim, the density of the materials, and some advanced calculus knowledge.

I am in Cal II and we are doing this problem in 2 dimensions with known equations. This would be an unknown equation in 3 dimensions.

Anyway... i guess i said all that to say ... there is really no way to tell besides testing.

 

IIRC, the 40lbs savings that you achieved, translates into a 120-160lbs saving. As mentioned, this is due to rotational mass factor, so it should translate into a .1-.2 sec reduction in your 1/4 mile times.

 

Im interested in this thread, I'm upgrading my wheels from performance model (26.5 lbs) wheels to the Nismo LMGT4's (18.1/18.8 lbs) wheels. I did the math on the weight plus tires ( kumho mx 245/40,275/40) which equals: 182 lbs. Stock = 220lbs, so im saving 38bs. Anxious to see what responsivness I get.

 

Anthz, do post your findings here for all of us to share!

 

it would still be 2D because the 3rd dimension doesnt affect anything. at 2.6" from the center, you have X inches^2 *density of the metal. and youd have to do the calculus every point. of course theres infinite points, and thats what calc is for, but you could never really figure it out exactly...

bout the most rreal world answer this can give is that on identical rims, spokes getting fatter as they go farther out would be bad. if anything, thinner as they progress would be better. but thin all the way around would be best.

 

moving from stock 18"(non rays) with 225 245

to lightweight 18" with 245 275

I lost 6-7lbs per wheel total.

can't really say I noticed a change in anything. just a bit less "sluggish" after I tryied a stock Z maybe.

no real acceleration difference at the track.

 

here we go with the ricer math

 

No kidding. That was one of the main reasons why i dumped my fat *** girlfriend last month.