Soundwear make great bags.
I use the 61 key version for my Tyros 3 and the 88 key version for my Kawai MP11 Stage Piano.
I've been dragging these instruments on paved streets and in hotel hallways, and up and down stairs and pavements fo 3 years now.
None of my instruments, nor the bag itself, have been damaged so far.
Just make sure that the bag is in front of you when going down the stairs.
That way, the wheels take the impacts
It's OK to drag it behind you when stepping off a pavement or just going down a couple of steps.
Great bags.
Best Regards,
Pianoman.