How many rivets on a wheel is "too much"?

[BHS_STopping]

I don't think there is such a thing as "too many" rivets when it comes to wheel tread. What we found out during competition was that the rivets at the end of the tread (where the seam is) tended not to do the job very well under heavy competition wear. A quick solution we came up with was to simply drill a couple extra 1/8" holes through the tread and wheel (right near the end) and put extra rivets in there after the wheel was completely assembled. They withstood competition much better, and it's a pretty easy way to fix tread that's fallen off during crunch time.

Edit: As for your riveting suggestion, that would probably work moderately well (but it's always better to construct things on the safe side). Just keep in mind that the connection between the tread and the wheel is only supported by the rivets and the tiny lips that the tread sits between on the wheel. Meaning, if your robot is being pushed from the side, a significant fraction of that force is going to be shearing the rivets holding the tread on. If you're lazy you could just drill new holes (through tread and wheel) once you already have the tread in place and rivet them that way.