My next bike: a tri bike or a road bike I currently have a mountain bike with thin road tires on it (because I ride only pavement). I’ve been starting to train for triathlons, here lies the problem. Should my next bike be a triathlon bike, or a road bike that I just put aero bars on?

If I go with the tri bike I still have my mountain bike for strength training 

If I go with the road bike I may need to purchase a new seat post
A road bike is more versatile. That would get my vote.