racing tires for si

I have a 2006 Civic Si and I want to start autocrossing it. What are the best tires I can get that I can use for the street and the track. I never drive in snow, but it does rain alot where I live so I need seomthign that works for both. What kind of mileage can I expect out of these tires if I am racing at least once a month, maybe more? Can I go with a different size than what the car came with.  

first THE BEST thing you can do when you start autocrossing is buy another set of tires wheels to race on. You don't want to kill your street tires on the track, and your track tires aren't good for the street. I responded to your other thread about suspension, and really id you have to budget for one or the other, tires and wheels is a much better option, if you can do both then thats even better.

For tires you will have several options if you go to a 225/45/17(Ibelieve your stock size is a 215/45/17 but fitment won't be an issue) The most aggressive choices are going to be either Avons or Hoosiers, they are almost full race tires. Both are going to like lots of camber so you would need the suspension mods to really get the most out of them. These tires are both pretty unforgiving so they may not be the best choice if you are just starting out in autocrossing.

More forgiving tires that will last a little longer are the Yokohama A048 and the Kuhmo VictoRacer V700. Both of these tires are going to be a little more proggressive when they let go and will give you a little more notice. They won't have the absolute grip of the Avons or Hoosiers, but they will be easier to learn on. Both of these tires will also give you longer life than the first two. The Kumho should be the cheapest by substantial amount.

Buy the lightest wheels you possibly can, I can't stress just how much of a difference unsprung and rotating mass will make, there are huge advatages to be had here.

One last thing, if you get the Kumhos, you will probably want to get them shaved before taking them out on the track. They come with a substantial amount of tread depth on them that will really hurt performance and tire life on the track. You will end overheating the tire and you will get chunking and uneven wear.