What are the lightest wheels? And which setup would be lighter? 17"s with tires? Or 18"s with lower profile tires?

 

Forged wheels.

Depends. Tires vary in weight. Look at tirerack under specs for tire weight.

 

Enkei RPF1 will always be the lightest and strongest for the price. That's why I got them, except I went with 19's because I feel 17's or 18's look way too small on the 2nd gen IS.

 

Some of the TSW rotary forged wheels are light. My TSW Nurburgring weighs around 20 lbs which is 8 pounds lighter than OEM. I had them on for many months going through bad roads in CA and autocross. They are still strong like new. I bought the TSW because it looks good, lightweight, quality, and affordable price.

If you only look for lightEST weight, Enkei RPF1 is the one to go with. I saw tons of these on other cars in autocross.

 

+1 Enkei,+2 TSW, +3 Vordoven Forme 1.
Are great light wheels or you can always go Forged..
Good Luck..

 

If maximizing accel. is your goal, go 17". The barrel being nearer the axis of rotation will reduce the moment of inertia. But 18" still looks better (IMHO)

 

For your information also, if you are looking for better lap time. Lightweight wheels don't really give you much gain over OEM wheels. The gain, if there is any, will be very small. The big gain in term of lap times is from BETTER TIRES. The more traction you have, the higher limit you can utilize the horsepower and corners faster.

If you are looking for "faster" acceleration, lightweight wheels again don't really gain you too much. It may give you a "faster feel" but not really faster even though people can argue about saving the unsprung weight is beneficial and all that. Reducing unsprung weight does make acceleration and braking "smoother".

In my experience on street and also on autocross, with the lightweight wheels, both acceleration and braking are "smoother" plus the steering feel is more "accurate" so the "fun to drive" factor is better than the OEM.

 

What is your budget for all 4?

 

I just recently switched from the OEM wheels to lightweight wheels for my track set up and it noticed a huge difference. I got a set of konig milligram 18X8.5 which weigh in at 19lbs compared to the 29lbs for the OEM wheels. I can't say the difference in lap times as I got better tires at the time as well but the car accelerates out of corners quicker and is much more agile. You have to realize that wheel weight is rotational mass and cutting that has a much more significant effect than just simply unsprung weight like taking the spare tire out of the trunk.

Also for the original question a 17" wheel with a higher profile tire will almost always be lighter than a 18" set up with a lower profile tire. Will also be much cheaper. The advantage of the larger rim and lower profile tire is better handling due to less sidewall. And looks of course!

 

awesome. thanks for the feedback everyone! i'll check out those Enkeis.
these would be my winter/drag wheels.
I have 19" Work Varianza T1S for summer. and currently use my stock 18"s for winter.
I notice a huge difference in acceleration. Not sure what I would be willing to spend just yet
since i'm basically only interested in them for drag racing. otherewise I would continue to just use my OEM for winter.
So I guess I would be more towards looking at the best bang for the buck wheel rather than just the lightest wheel. Just want one of the lighter 17"s available. don't even care if they're ugly as hell.

 

17" Enkei RPF1 is they way to go for you then. They are relatively cheap, really light, and 17's will actually grip better for drag due to the extra sidewall flex. Plus 17" tires are way cheaper.

 

From what the IS-F guys have posted online here, they can fit 17" wheels in the rear (with OEM calipers) AND a drag radial or slick with a lot of sidewall (which is better for drag racing). Perhaps a 16" would fit on a 250/350? The smaller the wheel, the lighter the possible weight + the wider selection of available wheels too.

 

I know I said I didn't care if they're ugly as hell, but a 16" on a is350? haha k maybe I care a tiny bit what they look like J/K I would entertain the idea of 16"s if they were super light!

 

TSW Interlagos are very light...im running 18s on my car each wheel is 20 pouds.. i have two 18x8.5 offset 20 right now still in box unopened ill let go for a cheap price!

 

Yes, it will look odd; but you can get a tire/slick with a sidewall that makes up for the smaller wheel size.

Check here are a pretty comprehensive listing of aftermarket wheels and their weights :

http://www.wheelweights.net/