I own a walmart bike for riding across campus (nobody's going to try and steal it off of a rack that way). The brakes suck in general. The cables were never stretched so by about the third time I used them they were gone and to keep them running at all the cables have to be pulled tighter weekly. The brake pad also contacts the rim awkwardly. However, I don't blame walmart. I purchased a crappy bike knowing it was a crappy bike (in fact thats the reason I bought it). I paid 63 dollars for the thing. I wasn't even expecting it to last as long as it did. If you're expecting to make this work you definitly need a lawyer. You won't be the first person to try and sue walmart for this and they'll probably have plenty of answers for your claims. That being said I hope your wife heals quickly!