Wheel sizing help! What should I roll with?
 

(title pun slightly intended)

I just got my 15x7 Kosei K1s in pretty good condition. I test fit them on (still need to get hub centric adapters) but they look nice. Only issue is the tire is a bit small, the guy was running 185/55s in the front and 195s in the back. I was thinking maybe I could get them a bit bigger, maybe to 200-210 range, but I read it might mess up the final drive. Speedo is already expected to be funky, but I want to know what y'all think. Mostly just looking for increased grip since I hydroplane whenever it rains or snows. I kind of want to run larger tires in the back, but not terribly large. Thanks.

205-50-15

I second the 205/50R15 It seems to be the standard. There are tire calculators that allow you to play with the numbers compared to stock.

205

agreed.

Thats what I run.

205/50 for sure. Lots of good tires available in that size as well!

Y'all are awesome. Thank you so much!! I'll run 205s all around then.

Note that hydroplaning could be WORSE with the 205/50x15 tire, depending on the tread pattern. Usually, hydroplaning is due to worn tires with very little tread depth for the water to be channeled out of the way. With a wider tire, that water has further to move from the center to the edges and could hydroplane at lower speeds, plus the fact that you're increasing the surface area and by doing so, reducing the loading. Point being, don't expect you'll fix your hydroplaning problem by going with 205/50.

Also, you want to run the same size tires front and back - it makes it far easier to rotate tires, and you'll get better tire life and tread wear by doing so. The one time I tried to run skinnier tires up front, they work out more quickly and I couldn't rotate them which wasted time and $$$. They were Pirelli P6's in 185 up front and 205 in the back on American Racing 14" wheels. Bad combo...