i left the 28 on the back, and it is just fine. seems tighter in back than front. don't know whether the studs would work in back, but mostly I worry about the front for ice.

the rim is from a CAAD8 but I imagine my stock rims would be fine.

I used to run fenders but they just didn't fit with 25s. had to put a 24 on the back. still got lots of pebbles rubbing in between tire and fender. not much for riding in the rain anyway.

next i will try a Michelin Jet Cyclocross