Back in early June, I got my first bike, a Trek 7.1 FX. I was liking it fine, but based on stories of speed increases with slimmer tires , I may have ruined it. I still don't yet feel comfortable doing tire installations because I'm afraid of reattaching the wheel incorrectly(a bit paranoid), so I went and had them done at Performance Bicycle. I had them install Continental Ultra Sport II tires in the 700x28 size. I knew they would make the ride a bit tougher and wouldn't have as much traction, but the bike feels too bumpy now, and I've nearly slid out twice coming down my gravel driveway, not something I expected even with slim tires. I have had them on for 3 days and 80+ miles and I am seriously taking them off and keeping them as a spare set, as I have seen an increase of roughly 1 mph which is not enough to justify the torture and loss of traction. I would just put the old tires back on, but I didn't think to ask to keep the old ones and the shop threw them out. After reevaluating what I want in a tire, my priority is traction on rough surfaces , absorption of road vibration, and speed in that order. I don't really know much about tires in general though and don't know much beyond smoother=less traction, rough=more traction. Does anybody have any recommendations for tires? What sizes can I reasonably fit? The 28's almost seem to small, but haven't given me any issues on that front. Approximately how big or small can I go with my tires?