wheel weight vs. tire width

Thursday night debate y'all. Which is more important, the lightness of your wheels, or the width of tire you can fit under the car? I come at a crossroads of seeing that I cannot afford both. I can either stay with the wheels I have now that are light, and yet only 7 inches wide, which keeps me at a narrow tire width. Or I can afford to upgrade to wider wheels that way quite a bit more. What to do? Current wheels weigh 13lbs each. I afford some in the 17-20lbs range. 
 

Edit: Miata. 

I suspect that the current strengths and weaknesses of the car as well as its intended use will influence the answer.  

I would prefer low weight on a low powered car, but accept higher weight if it's on a higher powered car.  

Wider will be faster, and provide a sharper steering feel. 

Didn't GRM run an instrumented test on wheel weights vs run times?

Autocross? Track day? What's the usage?

Obviously there isn't a hard answer here.  If you said each wheel was 150lbs extra then... no go.

13 to 17-20 is an odd jump.  None of the 15" wheels weigh that much, right?  And in the 17" world, 13lbs for a 17x7 seems very light.

Anyway, wider wheels + tires = better most likely

Jesse Ransom (FFS) said:

Autocross? Track day? What's the usage?

Autocross strictly with this one

ProDarwin said:

Obviously there isn't a hard answer here.  If you said each wheel was 150lbs extra then... no go.

13 to 17-20 is an odd jump.  None of the 15" wheels weigh that much, right?  And in the 17" world, 13lbs for a 17x7 seems very light.

Anyway, wider wheels + tires = better most likely

Correct. It's been awhile since I looked at them. They are 16" (nc), and 15 lbs. so 17lbs isn't a big hit in the weight dept?

Are you going to 17x9s?  That sounds about right. 

They should be significantly faster.  Plenty of national level STR NCs used to run the TRM wheels which are a budget option and not the lightest.  19lbs IIRC

If this is an autocross only car greater wheel weight is not going to overcome the far higher corner speeds the wide tires provide. Low wheel weight is most beneficial on bumpy surfaces and provides precious little inertial benefit relative to acceleration.

Classing comes in to play for wheel width.  STS allows 7.5" wheels, STR allows 9", and CSP has gone plum crazy with 11" wheels and 295 section Hohos.   Obviously the STS car will feel more "lively" but for ultimate speed, wider trumps weight.

I currently run a heavy Basset 15x10" wheel and next year will step up from 10.5" tires to something more like 13" wide.

Wider is basically universally better unless it's some kind of massive weight jump. And by that I mean like more than double the weight. And even then it'll still probably be faster, just drive kinda weird.

GRM had done some tests on these topics.

Do a search on andy holis' excellent tire tests, some of them have wheel width comparisons. 

There wheel weight test from a yellow miata, back around 2013-2015, which evaluated wheel weight.

Also keep in mind that wheel stiffness will affect your performance. If the wheel bends 1 degree in cornering, you'll need 1 degree more negative camber for ideal cornering grip, which negatively impacts straight line performance, so your ideal setup for that wheel will probably be somewhere in between, giving up a bit in cornering and a bit in a straight line.

A heavier wheel will likely be stiffer, offsetting some, all, or more than all of the performance lost due to being heavier, depending on lots of factors. This has been tested in a few magazine tests and shown to be true. In one, they tested a few wheels and even machined one to be lighter and it was slower than its unmodified version. I also recall reading about how the Corvette C6R team switched wheels due largely to stiffness.

Smooth parking lot, I wouldn't be concerned, but I can tell you that going from stock Neon alloys to Rota Slipstreams (nine-ish pounds, iirc.) on my IT Neon transformed the car over curbs through the chicanes.  It was like I'd bought another thousand dollars worth of shocks.

I scored on the FSP rabbit moving up to 10" with 255 Hoho's on panasport c8's that are crazy light in both wheel and tire.  Previous was 7" diamonds with 235 Khumo's that were like 16lbs a wheel/tire heavier.  Crazy difference between the two everywhere.