Originally Posted by BrianG

What speed are you wanting? 40-45 mph is usually in the ballpark of what most people shoot for. You can use this to get the gearing for the speed you want. Then, I'd get a couple spur options (spurs are cheaper than pinions) in case things heat up more than you like.

And personally, I'd go with an 8XL for 14 cells. 40krpm on the 7XL is a bit on the high side IMO.