[piscator]

I think you'll have to wait and see what kind of material is under the leather. Steam might work, but I suspect those dimples are cuts in the material underneath. If you want to eliminate the dimples, I envision that you'll need to fill those areas with something.

Are those 'dimple areas' hard or soft? I work in fiberglass, so if they're hard I'd fill them with a thick mixture of epoxy resin mixed with cut strands of 'glass and adhesive faring filler. A faring filler will be easy to sand to the final shape. The cut strands may not be necessary, but I'd probably mix a little in for extra rigidity.

If what's under there is soft (foam, maybe?) you might be able to cut, glue, shape, a similar material in those areas. Could be tricky, but probably do-able.

I just re-read that you wrote those areas are 'rubber' -- my guess is that the wheel is not solid rubber but a solid material with a rubber sheath over it. If that's the case, the epoxy filler will work. Whether it's metal or plastic, the epoxy will adhere to whatever material the wheel is made of. You'll have to cut the rubber sheath in the dimple area, fill those areas with the epoxy filler, sand the filler down to a dimension where you can glue rubber patches up to the same thickness of original rubber.

To make rubber patches to put over the filled dimple area, I'd use thin patches of a compatible rubber and glue them up one at a time, essentially creating a rubber lamination. Gluing several thin patches should insure that the rubber follows the round contour of the wheel and glues successfully. The 'memory' in a single thicker piece of rubber, might make it difficult to glue.

Of course, all of this depends on what's actually under that leather! Interesting project!

BTW: The application of epoxy/glass and sanding those 'dimples' would be about an hour's work in my shop (not including curing time). If you're unfamiliar or not comfortable with this part of the process, any local boat building or fiberglass repair shop would probably be happy to do this for you.

Lastly, having written all that you might be just as successful filling those areas with 'Bondo' -- but you can see where my head is at!