Hey all when considering how performance is impacted by tire/wheels, what would be better a 225/50R15 on a 19lbs rim or a 225/45R17 on a 17lbs rim?

 

Unsprung weight, the lighter the better. I would say go with the 17" it also offers a stiffer sidewall, better for turnin response.

 

Really depends on what you are doing with the car, if you are dragging I'd go with the 15's, but if you are autocrossing I'd go with the 17's. As far as drifting, I have not a clue or a care.

 

Well that's not a fair comparison.

The 15" rim with a 50 profile tire will have 1.1" less total diameter. The rotational inertia will be subtantially less. This will improve acceleration noticeably and high speed turn-in a little bit.

Taking the Kumho Victoracer tire for example, the 15" setup would weight 19+23.7 = 42.7lb. The 17" would weight 17+ 24.9 = 41.9lb. So your unsprung weight in this case actually goes down since the 15" rim is a pig in weight.

I would think that the 15" setup with a better wheel would be superior in most cases, except where you *need* a larger brake setup that would only fit under a 17" wheel. It all depends if this is a street car, track car, autox car, etc, etc. Not specifying that suggests to me it won't be a serious racer.

Really, I think stock FD wheels (under 16 lb/ea) at 16x7.5 with a 245/45R16 tire are an outstanding option if you don't need all the size of a 17 but don't want that piggy 15" you mentioned. The FD wheels are damn cheap, which allows more money for tire. I would spend as much money as is reasonable on tires before buying a fancy rim.

Dave

 

how about 235/40/17 - its quite a bit smaller in diameter than the 225/45, and 10mm wider. better in every way.

 

that is kind of an awkward size, not too many tire options going that route

 

235/40/17 isnt rare enough to cause a problem. tirerack has 20 different choices, and tires.com has some more. the 40 sidewall will keep the diameter down (main cause of fender rubbing) and is stiffer/more responsive than a 45. its all good.
235/40/17 was my first tire on 17's and it only got wider from there (im up to 255 F and 285 R)