even if you're fi.

 

lol, I thought common sense would prevail when I made my post. Or at least later, when I said this:

 

+1. I overstate this often in threads when people talk about "should I go with 20s" and such...but air and rubber weigh less than metal. GET LIGHTER WHEELS.

Edit: If speed is more important than looks.

 

with cars AND women.

 

5X5=25 lbs.--including the spare...hmmm...Actually, driving style is the número uno cause for lower MPG. Then engine out of tune, tire pressure, MPH,
clogged injectors, jack-rabbit starts, etc. Also, any stuff we carry around in the "trunk", if the space behind the seats qualifies for that name in our monZters!

 

are you sure? i thought it was more like 10 pounds is equal to one hp. unless your rule only applies to wheel weight?

 

It's not just a straight 5 lbs difference however. The 18" wheels are larger and the hub / spokes are not the majority of the weight on a wheel, it's the rim (round part the tire mounts to) that is the majority of the weight. The farther that weight is from the center the more HP it will take to turn that weight.

25lbs wheels in 15" vs. 25lbs wheel that 20" are not the same. The 20" wheel will take a lot more inertia to turn because the mass is so much farther from the center. This is why drag wheels are so small.

So when you drop 5lbs per wheel then go from a 17" to an 18" (all else being equal) it's not just a 5lbs weight savings. Some of that weight saving is being lost because the wheel is larger in overall size thus putting some of the weight farther from the center. So it's not quite as cut and dry as being 5lbs lighter.

Honestly, I doubt you would feel the difference between the 18" track wheels and 17" wheels. I went from 18" track wheels at 20lbs each to 19" Axis Matrix which are 25 lbs per wheel and to a much wider tire in the rear so another 2-3lbs in tire weight in the rear, plus a larger wheel so the weight was farther out now with a 19" and I can't tell a damn difference. The car hauled *** before and hauls *** now, it feels the damn same.

So will you feel it? I doubt it, i didn't and my weight difference is more than yours. My previous car was a Talon that ran 11.5 @ 119mph, CBR600rr 11.2@128mph and a Porsche Boxster so if the car was slower that I could feel I would have felt it. No doubt it would run slower in the 1/4 mile, but 2/10ths of a second doesn't register on the ****-dyno.

 

Andy's talking about unsprung weight aka weight of the components that actually makes contact with the ground. 10lbs off the body weight doesn't really do anything whihc 5lb off unsprung weight makes quite a difference.

 

If you put a 5 or 10 lb. weight in the car’s trunk, there is little noticeable difference in acceleration with a 300hp car.

If you add 5 or more lbs. onto the car’s rear wheels, the difference in acceleration is very noticeable. It’s simple Physics 101 that demonstrates the difference. Overcoming rolling inertia is very different than overcoming simple inertia. I believe that is the point others have made on this thread.

And… the farther the perimeter weight is from the center-of-rotation; the more difficult it is to overcome inertia. That’s why 20” wheels feel sluggish and why people who race use 17” wheels.

In fact a 17” wheel/tire setup and a 20” wheel/tire setup might be close in total weigh (more weight with a 20” wheels but less tire weight for the tire, and less weight with a 17” wheel but more weight with its tire), but in this case (when all else being equal), the17” wheel/tire setup has a significant advantage, which is less “center-of-rotation.”

--Spike

 

You beat me to it. Reps!

 

You're confusing power to weight ratio with rotational mass. In a Z, every 11.5lbs you shed from the car gives you an extra pony.

 

...anyway, I L-O-V-E my "Zee", give or take 5 pounds!!!

 

wow ... I opened a can of worms!!! so, basically even though the track wheels are 5 lbs lighter being 18" takes the advantage away... right? and I won't feel a noticeable difference ... ok thanks for the input

 

A 5lb. difference per wheel is HUGE. When I went from heavy PIAA 20's to 19" Volk GT/SF series wheels, I noticed the difference right away. Same thing whe I went back up to heavy Maya 20's.

 

to OP I went from my 07 wheels to 03-05 track wheels and I can tell a difference in acceleration..........very worth while....in my option

 

I honestly did not notice a difference. I went from an 04 base 17in rims to 18 in track rims (rays forged). I noticed when I had the rims in hand, but I did not notice anything from the butt dyno. Great mod though since it looks way better than the 17inchers.