I have a 1997 Cannondale F700 MTB and I'm thinking of replacing the pedals.Are my spindles 9/16 0r 1/2 inch?Thanks!

Typically, 1/2" are only found on 1 piece cranks.
Cannondale should be 9/16".

Stupid me!!I didn't think of checking the crank I just replaced with a Shimano Alivio!9/16 it is.

Don't forget to grease the threads of the new pedals to prevent them seizing and to torque them firmly with a proper pedal wrench to avoid them loosening and stripping the threads. I always use stainless steel pedal washers as an additional precaution against seizing and galling the cranks.

Remember that the left pedal has a left-hand thread.

Also, if the new pedals are serviceable I would suggest that you check them for sufficient grease and adjust them properly. It has been my experience that new pedals, even high-quality ones, come skimpily lubricated and adjusted too tight.

Bill got your answer. You can get a little plastic caliper for $2 that could save a lot of frustration down the road when you have to measure diameter (axles, seatposts, bearings, OLD on hubs, etc.)