I have been riding a Trek 8.3DS for about a year now and want to use it for a Spring Duathlon. I want to put some good road tires on it for the race (stock tires are 700x38). I was told I could go as narrow as 25 on the road tires. Do I need a different tube? I want a fast tire but don't want to risk excessive flats. I'm 6'-3" & about 215lbs. What advice would you all have for me?

ESM