Originally Posted by
twobikes
You put your seat back onto your bike and eyeballed it to get it straight, but when you ride the nose of the seat rubs one leg more than the other. When you put the seat back on, pull a piece of string taught from the center rear of the seat to the center of your stearer tube. This is much more precise than eyeballing it.
If the saddle has an ergonomic split, you can just lay a broomstick in the groove and line it up with the steerer, or kneel behind the bike and sight down the centerline of the groove until it's centered on the steerer (this might also work using the seat rails as a guide...I'm not sure)