Mine covers the tread. If thats what you are talking about. I'll post pictures of the back of mine tomorrow. The curve on the ring is a little after the tread in the back. Also when i put mine on I push back on it and hold it back really well when i tighten it. This is kinda trickey. But it gives you a tighter fit with the front cover. Maybe you should try that. Maybe your ring is just to far foward.

 

it does cover the top flat part of the tire, the thread, but you can see the curve that goes from the thread to the side of the tire and that side..... I guess that is best explained, I will post a pic but I need to take one first

 

that would help[8D]