Worked with a 9ft exercise training bar, standard thickness. That took regular exercise plates..non Olympic style plates. This was a very dead bar (no spring...non revolving) and mostly used for DL's and squats. Slapped 50, 75 to 100lbs plates on it and easy load to over 1,200 plus. Great bar for the raw strength lifts, no lifting finesse required.
Another 9ft bar was used only for squats, and after a while develop a curve/bend in the middle after too many heavy loads by too many guy's over the years. That curve made it a better bar by the way it fit the traps and shoulders. Can buy new bars with that slight curve built in.
With a well balance and better quality live Olympic bar, anyone should be able to use 20 to 30 more lbs in most lifts. The grip should develop along with the weigh used on the bar. If having trouble when reaching max weight, might suggest using straps (nylon) until the grip catches up. An axle bar helps greatly with the grip development. Neglecting the grip is not always the best of ideas when working out with serious intent, with serious goals in mind.
Good Luck..