Unsprung weight as it specifically applies to your wheel / tire combo.

A quick search shows 16x8 Enkei RPF01 around 14 # Toyo R888 in 255/50 r16 are 26#. For a combo of 40#.

So in a typical A,B,E Mopar weight loss of 20% on each corner is significant savings and lap time saver over a typical 50# combo.

Any thoughts on this aspect from those that might have imperical evidence on this?

I know tire and wheel weight is a huge issue for the SCCA and autocrossers. I believe in classes where available power is low its a critical variable.

Not only does the car have to accelerate the wheels, the brakes have to decelerate them. And yes, unsprung weight to boot. A pound in the wheels means so much more than a pound in the trunk or engine bay.

It appears the basics are shunned to the wayside when chasing after an appearance of being fast on a track.

Problem is there are no good 15" tires and even 16" and 17" are getting sparce.

I'm about being forced now into 18" rims because i'm worried about 275/40/17 losing selection soon.

Does a 3000# car really require a 275 tire?

+400ftlbs makes up for having a couple more rotating pounds. You could make the same argument heavy brake rotors. As with everything YMMV. With a power car the gains are diminishing.

if you have the power, getting/keeping the tire on the ground after a bump and in general being easier on the dampeners is where a light combination is beneficial.

I ran STC/STF with 135ft lbs... so yeah loosing 12 lbs/wheel(!!) was noticeable. in my +250ftlb SRT4 or Focus ST, i have better things to worry about. I suspect the same is true for the barracuda.

I'm at 3209 lbs on digital scales, so far. I think new vettes and vipers have as wide front tires in max handling packages. And they have better weight balence and lower cg.

C4 Corvette is 3200# with a really great distribution 51F/49R

Those are on 255/50R16 and there are plenty of tires in that size.

Maybe that is why Tom Quad liked that tire size squared up on the Black N Blue Charger and the AAR

I'm 3209 with 57.28F/42.72R distribution.

That's 206 lbs more on the front wheels. I bet the difference is even a little greater with driver.

90's Camaro SS with a more ponycar weight distribution ran 275/40/17's.

And we're up to C7 Corvettes that have Michelin Pilot Sport P285/30ZR19 front and 335/25ZR20 rear tires on the Z06 versions. With all kinds of lightweight components to reduce unsprung weight. Even C4's have aluminum spindles and control arms.

Ya none of the modern 200 treadwear tires we use for Autocross come in anything wider than a 225 for a 16 inch, or 255 for a 17. Meanwhile I can get 285 for an 18 and 305 for a 19. I would love to get the lightest 18/19 inch wheels possible, but sometimes cost is an issue. I believe tire size is one of my main advantages over the Mustang guys...

I hear that. All the good 255/50r16 tires are the Toyo RA1, R888, Hoosier wets and the rest are all real race tires Hoosier A/R6 and the Hankook race tire......nothing in 200tw.

I tried to be weight conscience when I was choosing wheels and tires. Since I didn't want to go with offset shackles just yet, I tried sticking some 255/40/18's under there. Probably the stickiest tire that comes in that are the Michelin Super Sports which are a 300TW tire. From what I understand is they're still a pretty good tire and the most lightweight when Hot Rod did the Hotchkis Taxi/Tirerack comparison. Unfortunately, there was really only one set of wheels that fit my application the best so I bought them. They're M/T SC-5's. They're very robust wheels so I'd imagine they'd weigh about 22-23 lbs. I was really shooting for Enkei's which would have saved me about 3-4 lbs a wheel. Tirerack says the tires weight about 25 lbs so I'm at about 48 lbs per corner of unsprung weight not including the brakes (big discs so there's some more into the mix).

Paul -- the combo of light weight rims/tires ads up to the micro-seconds if/when pushing it to the limits on timed competition runs.. the driver still has the final limits pending skill/experience and overall car setup. If/when possible and the budget allows... always go for the lightest rims... light weight rims typically increase in cost... there's some serious choices available if someone really wants light weight rims... The most serious competition racers will spend those big bucks ... as it always comes to the overall package... everything continues to add up towards that package.

I put Fikse rims on my '65 Coronet because they were light and strong. Not sure it really matters much since my car is a garage lizard, but the Fiske rims do look really cool sitting out there in the garage!

I read an article on one of road race magazine a while back where they tested a wheel that was lightened as much as possible vs. a normal wheel the particular wheel company sold on the market. The result was that even though the wheel was lighter on all four corners, the lap time was slower due to the additional deflection. The normal wheel was heavier but was also stiffer and was able to handle the loads better which led to a faster laptime. All the hard core road race S2000 drivers on the other forum I go on all use the widest wheel possible that can fit on all corners. Even though it is heavier, they are able to produce faster laps as well.

the enkei rpf1's are about the cheapest, lightest race rim you can buy right now, after those the price go up significantly, but thats the cost of custom offsets as well.

We tried that before with our SAE Baja car. The wheels we used were smooth-faced, spoke-less wheels. We gun drilled about six 2-3" holes into it to save weight. Although, it did make the car a little faster, those specific wheels were prone to bending and failed much quicker. That's why we kept the old design wheel and didn't modify it.

The manufacturing process of wheels make a difference too when choosing a wheel. Some of the high dollar wheels are expensive as they are due to the process. From my experience, same material, a Forged wheel will have better mechanical properties than a Cast wheel. As far as I know, Enkei's are all cast, but what makes them more superior vs other cast wheels is the material they use.

and pricey!!!

There are wheels that use flow formed technology and HLT are lighter than cast wheels and stronger than cast and cheaper than forged.

http://www.tirerack.com/wheels/tech/techpage.jsp?techid=90

Next how much can diameter increase destroy a cars track times? Like going from 215/45r17 on this brz with DZII to 245/40 R18 DZII'S appeared to here:

http://www.roadandtrack.com/car-culture/a18334/scion-fr-s-tire-transformation/

So all things equal how much of a tire width increase would you take for an addition of weight and I see what the 200tw tires forces you to increase wheel diameter to get into 275 and greater width tires.