The road condition from Kathmandu border to China border Zhangmu

How is the condition between the two borders? If we are travelling by trolley luggage bag will it be any problem or difficulties of carrying it? Is the road condition okay for pulling the trolley type luggage bag? Or is it better to carrying haversack type?

We are going end of May 2013 to early June 2013, how is the weather there?

Very much appreciate for the answer above soonest possible. Thank you..