650x23 vs 650x25
 

Just got a pair of Continental Grand Prix Triathlon tires (650x23)......the tires I use to have were Bontrager Select 650x25. Seems like these Continentals are not going to go on. Am I trying to do the impossible? Can 23's not go on the wheel the 25's were on?

Should be fine. My Conti GP 3000´s are a bit snug but go on no problem.

Just to check - you have let all the air out of the inner tube, haven´t you?

I have a little air in the tube just as standard procedure when changing one out, but I may need to let more air out of it, or just no air at all w/ these new tires. I also read that w/ new tires, they may need to be stretched a little and until then, they will be snug w/ getting them on. I just hope I don't get a flat on raceday b/c they will be a pain in the ass to get on.

Get all the air out of the inner tube. Shake the inner tube around in a bag with some talcum powder. Install carefully.

Any air in the tube at all is going to make installation very tricky.

The best way to stretch the tyre is to get it on the rim, get it up to pressure, and ride the hell out of it for a while.