What tires and what pressure are you running?
I think the stock cyclocross tires that came on my Jake had some ridiculous max pressure rating of something like 55psi. At 220-230, I ended up running 75psi offroad and 85 on. I'm running 35c panaracer passelas right now at 90psi, and at 205lbs, they look much better. I may actually go down to 80psi with them.