I've been carefully considering my Z's wheel options. Some days I want to go for performance, and other days I want to go for looks.

Looks are easy to measure, but performance is not. Finding an up to date, difinitive resource for wheel weight is like pulling teeth. Futhermore, what REALLY matters isn't wheel weight, but a wheel's rotational mass. And to figure the rotational mass of a wheel, you have to know the wheel's mass distribution- which of course is even harder to find than the weight.

Do any of you fine folks know where I could find such information? Volk rims are generally lighter, but HREs generally look better. If their rotational masses are similar I'm springing for the HREs.

 

well. overall wheel weight does play a role in your search for rotational mass.

obviously the heavier it is, the more mass there is to spin!
also you have to take in consideration that multi-piece isnt necessarily better (in the sense of weight) than a single piece forged rim.

Cast is generally heavier (think TSW, Konig), Forged as in Volk/Rays and some 5zigen rims.


as for your wheel weight URL, try this one, i like it alot
http://www.wheelweights.net/

if you want looks and power, try going for the FNR01C from 5zigen. IMHO HREs are over rated and too pricey, and never listen to someon who said Rays are 'played' out. Mackin Industries. the only way to go for quality. HA! i sound like a commercial.

think tho. are you REALLY going to track race the Z in 19s? obviously not. even if they are light. its pretty stupid, tire costs would cost as much as the rim twice changed.

get a set for looks. a set for track.

 

man if you actually lived somewhat close to me I would be buying you a beer, well a few actually! I couldn't agree more with your two statements!

when I read some of the posts about wheels and tires I cant help to laugh and shack my head! so many people are concerned about aspects of wheels and tires that they will never even benefit from or be able to experience! I'm willing to beat that 96% of us here will never be able to push the tires anywhere close to want they are designed for but yet guys are sooooo eager to spend hundreds of dollars per tire to have them....why...so you can just say that you have them???

seriously, I'm not looking to open a can of worms on this but the majority of people don't even live close to a "track" let alone frequent one! and tracking a 19" rim or tire????????? so when are you really going to use that $250+ tire that is designed for pro and circuit racers???? in rush hour bumper to bumper traffic to and from work Monday through Friday? to the mall or park on Saturday or Sunday?

sorry , I know I'm just ranting but if you think about it its pretty dam sad. the prices of the market today are so dam high b/c people will literally "buy anything" and the manufactures know it all too well! they know people now would rather spend $x00s more for a name or logo Vs just buying what they actually need!


ps
sorry Fëanor, I didnt mean to take your thread off topic.

 

I 2nd that. I will track my car once in a while so that is why I am going with 18's. And, I am going with the new Yokohama AVS ES 100 tires. The set of 4 is costing me $630 shipped in a 245/40/18 and a 275/35/18. Can't beat it. But I am in the same position narrowing down a set of wheels that aren't too expensive but still light and look good.........I'll let you know of the outcome....

 

Yes, mass = weight x gravity so the rotational mass has something to do w/ how much the wheel/tire weighs.

 

If you are performance minded, beyond wheel weights... you probably want to examine the wheel construction...

If it looks like there is a lot of mass out at the edges (spokes widen as they go from center to outer rim, for example), it probably has more rotational mass than the opposite (less material at outer rim than at center).

Also, note that this only matters for the rear wheels... the wheels getting power from the motor and thus resisting that rotation.

I think the suggestion of having two sets of wheels is the best, though. Buy your new wheels for looks. If all else fails, you can always use the stock wheels for track until you can grab some inexpensive light weights later.

 

definately an oxymoron... There is never an inexpensive light weight unless its like a 15" rim.

you get what you pay for.

 

I won't pretend to tell you guys that I'd ever really notice the difference between wheels. But I do want to make sure my money is well spent, even in ways that are beyond my means. If you think too utilitarian, you end up sporting a $50 powder coating job on the rims off a '77 Oldsmobile station wagon.

Here's the general idea. A 10lb rim with 9.9lbs at the outer edge will give the engine/brakes more resistance than a 20lb rim with 19.9lbs at its center (these aren't realistic weight distributions, but it gives you the gist of it). Wheel weight IS part of the equation, but it is not the deciding factor.

This is one of the reasons I'm going to buy 18" rims and not 19". Larger diameter rims gain all of their additional weight at their outer eges, since the center hub remains unchanged. I'll never notice the difference in handling, but any half-witted jackass can learn to shift and floor it.

 

This is very true. Don't overlook that the larger wheel has the actual rim further out from the center. This also means more mass further out from the center and a higher polar moment of inertia. A bigger wheel means more mass further out, simply because of this.

The bottom line (performance-wise) is that you're better off with a good compromise of overall weight, overall diameter, rotational mass, and handling. I won't go above 18s because of that compromise.

 

Here is a Mr. Wizzard experient. Tie a rock to the end of a string. Spin the rock around with your hand close to it. Move your hand slowly away and feel the true essense of rotational mass. IT is quite a bit harder to get that little rock moving when its 6feet away from your hand.

 

Right, however if you have a wheel/tire combo that is like 30% lighter than a smaller wheel/tire combo that is 1 inch smaller, even though you have more rotational mass further from the center the overall diameter is the same (because the wheel and tire are +sized). So basically you have to take the tire into consideration too.

 

Let's not get into this on THIS site now. This can get really complicated and I haven't the energy to exert on the topic. lol

The overall diameter IS the same, but there is still more mass towards the outside edge of the wheel/tire combination. The wheel rim metal will have more mass affecting the polar moment of inertia than the tiny bit more sidewall and air that comes with a smaller tire (fitting the same overall wheel/tire diameter). Make sense?

 

LOL.. you're here too? We already went over this. A 19" wheel is always going to have a higher polar moment of inertia than an 18" wheel. HOWEVER, if the 19" wheel/tire combo is MUCH lighter than the 18" wheel/tire combo the 19" wheel/tire COULD possibly have a lower polar moment of inertia and thus have BETTER performance than the 18" wheel/tire combo.

 

Let's put our minds into use!

Take the 19" TE37s desired by many. If per say, you have the 18" stock Track wheels (also forged Rays but slightly heavier), would the 19" TE37s have higher rotational mass? If my memory serves me correctly, it is sized +1.

 

Not true, the energy to start the front wheels/tires rotating still has to come from somewhere. It comes in the form of resistance from the road/tire contact patch and that resistance has to be overcome by the engine. The fronts are just as important.

Here is my problem right now. I am looking for a race rubber setup for my Track model. 18" race rubber is impossible to find in the right sizes for a good front/rear balance not to mention outrageously priced. Looking to go with a good 17" setup, any recommendations for a 17" wheel that is relatively light, clears the Brembos, strong, available in correct offsets at 8.5-9" front and 9-10" wide rear? Looks are not a priority here.