After riding a Bianchi 52cm road bike for the mjority of this year, I decided that with winter coming (Chicago), I might want to check out trails for when it gets too cold to ride on the street..and for fun.
So I find sompleace that has 2004 Trek Fuel 80s for $720 and I get one. I am almost 5' 9" and have a 30 inch inseam. The guy at the shop told me that the 15" would suit me fine...so I go with it.
I go for my first ride last friday at Palos and have a blast for an hour and a half.. halfway through though, I notice that my seat seems lower than it was when I started. I raise it back up to where it comfortable (I don't think they counted on someone weighing in at 220 jumping on it...lol) and notice that I am about 1/2 an inch above the max line on the seat post. I don't think it is a good idea to put that much stress on the frame.
They will take it back and give me the 17.5 (with the post be much longer?...doubtful). My issue is that I am pretty happy with the size of the frame. I felt comfortable, had minimal hand numbness (a problem for me on straight bars..that is what sent me to a road bike in the first place when I decided to get some health in my life) and didn't feel cramped. I did almost go over the bars twice but I think that it was more my stupidity than being out of balance.
How am I going to notice the difference in size? Is riding a frame that small and just getting a longer post a bad idea?
Did you try a larger bike when you bought the 15"? If not, ride the 17.5" and see if you like it better. If the 15" feels better, just swap your current post for a longer one. If you like the bigger bike better, make the switch.