The Trek 3700 is a big step up from your 820. The 3700 is lighter with better shifters and derailuers. The other plus is that the 3700 components will last longer.
I have to warn you. I am gonzo crazy when it comes to quality bikes.
I can't tell you what you should do. If it were me, and I could afford to upgrade to the better bike, I would do it in a heartbeat.
“No one has ever drowned in sweat.”
"The strongest have their moments of fatigue."
"It ain't bragging if you can do it."
" Not everyone who looks fast really is, and not everyone who looks slow really is."
| Pounds lost: 86.0