Check the interior width of your rim. It should be noted on the label somewhere on the outside. It should say something like 559X20, 20 being the interior width.
Then, go to Sheldon Brown's website and look up tire sizing for your width rims. It will tell you what size tires will best fit those rims.
Schwalbe Tires has similar info on their website, under Tech Info.
I'm betting you will have lots of options......probably everything from 1 1/4" (32 cm) up to whatever your fork will allow.
No more guessing.
Last edited by Wanderer; 10-02-08 at 04:43 PM.