i don't think that's relevant....

if i can spin a wheel/tire combo A more easily than wheel/tire combo B when the car is in the air, why would the energy required to move the total weight of A versus B, when the car is on the ground, decrease?

other than factoring in the load bearing on the wheel/tire combo due to the car being on the ground, i don't think it changes unproportionally....it would still be a proportional difference.

btw guys, the 18" SSR's are actually something like 7 pounds a wheel lighter than stock

 

If you had a different amount of friction (ie contact area with the road was bigger/smaller with wider/narrower tires) it might be relevant.

 

I was thinking primarily about the change in diameter of the wheel and tire combination. If you have a greater diameter, you have changed the gearing. It appears to me that most have changed the overall diameter when changing to larger wheels/tires (observed by the filled wheel wells look).

And, yes, someone else did mention putting the weight out at the extremities of the wheel by going to a larger diameter.

Sorry, I'm not a fan of huge wheels unless you have huge brakes that need the huge wheels - e.g. new 19" Porsche situation mentioned.......and speed capability that requires the big brakes. Therefore, generally speaking (not always - I agree), you are decreasing your performance by going big.

BTW, if you say that wheel x weighs less than stock and uses the same diameter tire as OEM, then I agree that you will have better performance provided there has not been too much weight migrating to the outer edges.

However if you go to an aftermarket wheel with stock diameter wheel but lighter and lower profile tires, then you will have even better performance......too bad the wheel co. are not heading that way. Show and not go appears to be the marketing ploy....most of those large dia. wheels are understandably heavy.

Reijo

 

I don't know about that. Many (most?) people that go to larger wheels also lower their car which is why the wheel wells look more filled-in.

 

Geez, Vlad, who'da thunk such a simple question in a regional forum would lead to such an involved thread and input from an international crowd.

Anyway, I think a few of us are moving off into a tangent (pun intended ).
We need to keep certain things defined or we'll go nuts trying to figure this out:
"Most" owners, when going to a larger diameter wheel, will pick a tire aspect ratio that will keep the SAME wheel/tire diameter so that the speedo does NOT incur too great an error (at least that's what I plan to do).
For now, let's keep widths of rims the same when going to a bigger diameter and let's keep the tire contact patch width the same also, so we can deal only with the affect of increasing the wheel diameter.
Also, for now (before we inject another "variable"), the weight of the bigger rim is the same as the smaller rim.
If we start to inject things like wider rims and wider tires and different wheel/tire diameters, this only adds variables to the situation that becomes too complicated and digresses from the original query.
Keeping the above in mind, my premise is that a larger diameter rim will push out its weight (even if it's the same) further from the spinning axis. It is agreed that 1" won't contribute a significant difference in the "effort" to spin it but is there a difference at all? So, to make the comparison more dramatic, let's use this model:
Put hand cranks on the axles of 2 wheels, both wheels being 20 lbs.
1. One wheel has a diameter of 10".
2. One wheel has a diameter of 100".
Which one do you think will take more effort to crank to get it going, to keep it going and to get it going faster or slower?

Now, let's throw in the variable that we've all been talking about (well, most of us anyway):
Same parameters as above BUT, one wheel is now only 10 lbs. Now answer the same questions.

 

but you can't vipe.....the disparity in the sizes is too great for our purposes.

why do a comparison of 10 vs. 100, when we only need a comparison of 10 vs 12??

and, you CANNOT discount the weights....that's what it's all about.

don't you know anything??

 

Just trying to start off simple to get the point across before throwing in "real world" wrenches.

 

 

Maybe this is the easiest way to put this to anyone considering wheels.

-Try your best to keep the overall diameter the same as stock. If the diameter is smaller, you will effectively lower your final drive ratio. Worst case, go smaller rather than larger. Try to keep it identical to stock.

-In conjunction with the first point, keep in mind that the width of the tire, as well as the profile, play a role in keeping your spedometre accurate. Miata.net has a tire calculator that is extremely helpful. Use it to compare stock to aftermarket

-If you care about performance, try to keep the wheel weights lighter than stock. If a stock rear wheel is 18 lbs (for example), an 18 inch wheel that is also 18 lbs will still decrease performance. Simply put, the lighter the wheel, the better for performance (without getting into anything too technical)

-If you care about wheel quality, a forged wheel is a better bet. cast wheels are not of the same quality. the stock wheels are cast. cast wheels, incidentally, are also heavier (generally).

-If you are "racing" your car, and maximum performance is your concern, a 16 inch wheel is your best bet.

-If you want a good mix of looks and performance, a 17 inch wheel is best suited.

-If you mainly just cruise around town in your S2000, and looks are most important, an 18 iinch wheel is your best bet.

-If you are a drug dealer or what have you, a 19 inch wheel is best.

 

I think a point that was missed through all of this is driver ability. I can guarantee you that a great many of us could put the lightest wheel/tire combo possible on our S2000's and some guy or gal out there with heavy 18" wheels on their S2000 would still badly humiliate most of us (including me) on the track or street based on their skill level. So very few of us are track oriented yet are are so compelled by the prospect of having a few extra unsprung pounds on the corners ruin the performance of our cars. No one has really discussed the handling benefits of a larger footprint wheel, that would be the main reason I would upgrade from the OEM 16/17 inch wheels.