Hi, have only been to Tire market once a few years ago now.
Its a very big market and quiet crowded, parking in the near by streets is possible no problem.
As for wheelchair uses the streets are the same as other areas in Turkey.
The market would be difficult with a wheelchair only because of the narrow areas and crowds, but from what I can remember you would be able to get around on the roads.
Hope this helps, a very pretty area and a real Turkish market not touristic....well they where quite a few Americans there but no coaches.