[AFRichZC6]

@strat61caster has hit all the big points. I'm just going to piggyback on it.

Originally Posted by Strife26

I was looking at getting 18" wheels. I did some AutoX and it is very easy to understeer with stock tires. Yes, I know it is the driver too. A lot of it is me pushing too hard and not driving well, but the stock tires don't help. I have only had understeer issues at the autox course(s) so far.

The stock tires DO help you learn! You'll learn to control the car better at the limit when the limits are so much lower on the stock tires vs sticky ones. With stickier tires, the limit is higher, and they will be less forgiving when you eventually exceed that limit. I'm a believer of the whole "the easier to learn, the faster you learn" philosophy.

Originally Posted by Strife26

Would upgrading to 18x8/8.5/9/9.5 be a good upgrade, or should I stick to 17" wheels with new rubber, or 17" and get wider wheels?

I planned on getting 18x9.5 in the rear and 18x8 in the front to fill in the wheel gap and get better traction, but I don't want to wait to buy my wheels and the set I was looking at was more than I can spend right now.

I am making absolutely sure that the wheels weigh less than the 17s I have. I have a series.blue and from my research the wheels are 19-21lbs each. I am looking at the Motegi MR131 Traklites. They only come in 18x8. The price is nice, and the weight is even better! I don't necessarily like the wheels, but the price + weight are nice, so I figured I would go with that.

Is there any reason I shouldn't go with 18"? Is 17" > 18"? And lastly, should I go with something that is 18x9.5" in the rear, or will 18x8 (all around) do the trick?

If you get a staggered wheel/tire setup, you'll likely just get more understeer. The guys in in STX usually run a square setup - typically 17x9 with 245/40R17. This will offer loads of traction when combined with some more camber adjustment. I'd play around on the stock setup or a CS-prep if you're still learning. I compete in C-Street with a second set of 17x7 wheels with my autocross-dedicated tires.

I haven't seen anyone competitive in our region in CS or STX classes with 18" wheels. Tires will probably be more expensive too. It's not worth going to 18" wheels unless you want the look or if you are going to run something wider than a 255/40R17, but you may want more power to make up for increased rotating mass.

I do about 4 or 5 events on stock wheels and tires before I started adding the OEM camber bolts, front sway bar, and got a dedicated set of used wheels and tires. A year later, I got Koni dampers.