Join Date: Apr 2015
Location: Hillsburgh, Ontario
It's recommended to replace chain when replacing sprockets and to keep both sprockets and the chain on the same timeline so that you don't end up with uneven wear, etc.
My bike has a 15t front sprocket, and it makes it more fun for street riding, faster off the line kind of deal, but will lower your top end... which you can't use on normal streets anyway, right?
Going down 1t in the front is roughly equivalent to going up 2t in the back. I've seen often enough to do both at the same time, and I think I will try bumping my rear 2t on my next sprocket change. Again, faster off the line, power is more readily available, but will top out sooner. Also, will be louder and work harder (higher rpm) at steady speeds, so for instance will have to maintain higher RPM on hwy speeds if you do a lot of hwy riding, but -1, +2 shouldn't be enough of a change to excessively tax the engine for normal hwy riding.
Be smooth, then be fast.