This is my first post here. A little background; I live in the Netherlands and cycling has always been an intgral part of my life, not as a sport, but as a part of daily life. Until now (I'm in my mid-30's), I've never even owned a car.
Not too long ago my Gazelle city bike was fitted with 50mm (622) Schwalbe 'Fat Frank' tires on a standard 19c rim. Unfortunately, within 48 hours, I got an unexplainable flat rear tire (see photo). It did not happen while I was riding my bike, but I found out about the next morning so it wasn't a sudden flat. I checked the tire and tube thoroughly, but I couldn't find any sort of damage of puncture.
Since the Schwalbe tire was 50mm and the rim was a rather narrow 19c, I'm beginning to wonder if perhaps the tube 'slipped' between the rim and tire and thus was ripped apart which caused the flat. In general, opinions about fitting wide tires to narrow rims differ. Some say it's not a great idea, others say it is not a problem. At least according to ETRTO norms, it shouldn't be a problem. I a bit worried though if it a good idea.
Does anyone has any insights to this matter? Is it in general a good idea to fit 50mm tires to a standard 19c rim?
I was concerned about this when I converted my Workcycles Fr8 (which has Fat Franks) to an electric bike and switched to a much narrower rim (with the hub motor) than the stock Workcycles rim. I was comforted by the ETRTO standards, though I noticed that Sheldon Brown has a much more conservative chart: http://sheldonbrown.com/tire-sizing.html. I was also reassured by my local bike shop that the rim/tire combo would work. I've been running the wide tire on the narrower rim for 6 months with no problems. However, my narrower rim is 23mm, so it's wider than yours. I would hesitate to put the Fat Franks on anything smaller.
Your rim is 19mm internal width? You should easily be able to use 40mm (actual) tires. The Schwalbe "little Big Ben" is available in 40-622.
The Fat Frank in 622 (700c, 29er etc..) is a claimed 50mm, it probably measures 47mm.
You are over suggested width, but some get away with it. Usual problem is stability of the tire on the rim.
I can't see what's going on in your picture, it's too dark & undefined on my screen.