What causes a bike to wear to the edge at the rear tire but not at the front tire? And vice versa? I've owned several bikes and some will wear to the edge on the front and the others to edge of the rear but not too many have worn to the edges on both tires evenly. I'm guessing geometry, tire size, etc. Is there a general rule of thumb?
It's purely tire profile. The front sidewall height is 70% of it's width, while a rear's sidewall height is 55% of it's width.
Wouldn't geometry affect this too? It seems like when I've raised the rear on a bike, the contact patch at the front moved more towards the edge. (Could've been that the bike handling improved and lean angle was higher.)
The sides of front tire wear hardest when you turn in, before you get on the gas, (when most of the weight is on the front tire), and the rear tire wears most during acceleration after turning in, and expecially exiting the apex, (when most of the weight is on the rear tire). If your rear tire has smaller chicken strips than your front tire, this means you're not going into the turns as aggresively as you are accelerating out of the apex. For street riding, this makes sense. After all, if you're coming out of a turn too hot, you can always back off the gas. But if you're going in to hot, it's not as easy to recover. Most of us are better at accelerating out of the apex than going in. This means more tire wear exiting than entering, and since most of the weight is on the rear tire during corner exiting, the rear tire will show smaller chicken strips than the front tire even if lean angle is constant going in and coming out. And while lean angle should remain constant throughout the turn, many riders turn in too early, causing them to run wide. To get back on line, they're forced to increase lean angle after the apex, which means they're running a greater lean angle exiting than entering, which also causes smaller chicken strips on the rear tire than on the front tire. Save the really hard braking/corner entry for the track, where miscalculations aren't so costly.
