What is the max weight a standard bycycle would take?
178kg would put significant strain on most off the shelf bicycles. Most critical parts would be wheels, bottom bracket, crank set, and suspension if any.

I would suggest that you go to your local bike shop and have custom assembled bicycle for you with:


wheels 26" with at least 36 spokes, best quality double walled rims, best quality spokes and good wheel builder
robust steel frame with no suspension
wide tires
bottom bracket and crank set with external bearings like Hollowtech II, or better