Gear Combo Guru
Join Date: May 2007
Bikes: Spec' Tarmac (road), Ridley Fenix (commuter & fast tourer), Salsa Mamasita (MTB), CoMo Speedster (tandem), Surly Big Dummy (cargo), Airnimal (folder)
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You must match the fork column diameter, which probably needs to be 1 1/8". Then you need to match brake mount type, which should be OK for a hybrid and a CX fork. So as not to alter the handling of the bike, you need to match the axle to crown length of the old and new fork and the rake. If not, it should still work, but the bike may become faster or slower to respond to steering input.
To change forks, you need to know how to and have the tools for the following tasks: Remove crown race, install crown race, cut the steering column to the correct length, and install the star nut (or some other mechanism if the steering column is carbon). These re not simple tasks and are made much easier by having the right tools. It may be best to have your local bike shop do the work, and if that is the case then you'll also need to buy the fork through them; then can also then advise you as to which model is compatible with your frame.
As for tire clearance, it depends on the fork. Some may only take 35mm tires, other models 50mm tires.