I was wondering what are the widest tires I can fit on the Alex DC 25 wheels. Currently I have 700 x32 on them and want to switch to knobbys because I ride on some unpaved trails during the weekend. What are the least expensive tires and widest I can go? Thanks in advance!
I'd expect the limiting factor to be the clearance from the tire to other parts of your bike's frame and components. Check for the smallest clearance from your current tires to your fork, chain stays, seat stays, brakes (if appl.), etc. You should be able to increase the tire width by almost twice this clearance.
Sheldon's site has a table showing recommended tire widths for different width rims, but in practice the recommended sizes can be exceeded substantially without any problems.