Currently I am running 700x23c Michelin Pro2 Race tyres front and rear on my roadbike, I love the tyres but recently (after lots and lots of practicing) I am finding that I am getting the feeling that I want a 700x25c on the rear at least, or even run front and rear as 700x25c. The feeling that is causing this is that I can feel the rear tyre wanting more grip in corners. I have been practicing and practicing recently, and have taken a lot of kindly provided tuition from a couple of very experienced racers in my club. I have definitely reached the edge of my tyres performance in terms of how hard I can corner. I can feel the rear wheel scrabbling at the edge of traction quite often when I am really hammering, and have crashed one in practice when it slid from under me. Luckily my bodyarmour stopped me getting seriously hurt and I walked away with some road rash on my thigh and the need for a new torso+arms rig. and new knee pads. But I can't wear it on a long ride, because of the heat I generate inside it, so I want to stabilise the rear wheel if I can, by getting more grip. I weigh approx 73kgs in summer cycle kit. I have a few questions: 1) Would putting a 700x25c on the rear (as one of the guys at the club who is VERY good suggests) help me wring an extra little bit out of the bike. I *feel* as though it would, but has anyone any experience? My gut feeling is usually very accurate, but I'm hoping someone has some experience before I lay down the cash!! 2) If I fitted both wheels with 700x25c's would I notice an increase in rolling resistence. Or would this option allow me to get that little bit extra with virtually no ill effects to my rolling resistence? 3) Should I just accept that I have reached the limit, I am now faster (when I want to be) through corners than nearly everyone I know, to the point where I have been asked how the hell I am doing it. Should I stop trying to push the envelope before I seriously hurt myself and be happy with what I've got?