You have pretty standard 700c wheels, which is the starting point for getting correct wheels for,your bike. 700c is a designator for standard road bike rims the diameter of which is slightly smaller than older style 27 inch rims. The other common designator, and a more descriptive one, that you'll see is the ISO standard 622mm. In any case, if you buy 700c wheels, they will work with your bike. Beyond circumference, you'll want to pay attention to the interior width of the rim, which determines range of tire widths you can run, and depending on the type of bike, there may be limitations with regard to how wide a tire you can run. See attached for more info. http://sheldonbrown.com/tyre-sizing.html