I bought a 15" virgo rim from the junk yard just because it was so rare, and then ended up mounting it on my car 'cuz the tread was better than mine!

I currently have 195/60/R15. Now i need to know which tires to get. Also, what advantage would there be in going to 205/70R15's? Here are my driving conditions, since i know everything is a compromise:

Performance: Even with the worn, flat tread on these tires, i've never taken turns hard or fast enough on dry pavement to squeal the tires. Part of that might be becuase i'm afraid of sudden massive understeer, since the front tires are bald. If i had good tread, i'd push it a lil more, cuz those curvy roads are just calling for fun.

weather: here in fresno, we can get a heavy wet season, but most importantly, i go to the high sierras a lot through deep snow, reasonable mud, dirt, and rock.

Overall, most of my driving is city/highway and paved country roads. a tire for that that will also accompany bad dirt roads with rocks, and what not is what i'm really looking for. As for the Snow, i figure i can put chains on the rear, and maybe the front too (I'll put in the effort if it guarantees me more traction.)

thanks for your help. I know there's another post out on tires right now, but i'm curious to see if anyone else out there has such a sharp contrast in driving conditions like me!