I started at about your weight, and did a few things.
-bought some heavier duty wheels, Atlas with 36 spokes. Mounted 'em on an old Cannondale M500... but ended up riding my Surly LHT and Montague Paratrooper, also with heavier duty wheels than they came with.
-limited my bicycling at first, hiking and walking mostly until I got below 300. I did take short rides, but really was kinda scared to mess up my bikes.
As I dropped weight, I tapered my walks/hikes and started to ride more, and now at around 240, riding almost exclusively.
I do still get a couple walks in per week, though. It can be convenient and can help with bone density.
At times I got pretty disheartened, and felt like giving up and diving in to cornbread and Snickers bars. I didn't, though. I'm sure you can do it if I could.
I still have a bit more to lose, but feeling SO much better! I have a thread on here, too.
