I am participating in a Coast to Coast bike tour next year using my 2007 Specialized Ruby Pro 50/34. I had a bike mechanic change my gearing from a 11-27 to a 10-32 to help me climb hills a bit better. He replaced my 23 mm tires with 23 mm Continental Gator Hardshell tires. My friends have 25 mm. When I surf new bikes, most have 25 mm as well. Will my 23 mm be alright or should I switch them out to 25 mm? What is the advantage and disadvantage of both sizes? Any advice and input is appreciated.