[piscator]

Have you considered just leaving it and recovering? I wouldn't find those 'dimples' objectionable.

As I mentioned, I doubt that the wheel is rubber all the way through. I'd use a 1/16" (or smaller) drill to see what's under the rubber covering and how deep it is. Rubber, vinyl, soft plastics (like modern impact bumpers) are tough to fill, although there are speciality fillers you can get from autobody supply houses that sell to the trade.

If you really want to fill those, your best best is to get down to what ever's under the rubber.

I've spent untold hours fabricating stuff that certainly wasn't worth the time and effort; simply because I enjoyed the challenge. To me, what you want with this wheel, doesn't make a lot of sense, particularly economically -- unless you just want to do it for the challenge.

It would be a whole lot simpler and economically sensible to leave the dimples or replace the wheel.