After way too much thought, I think I am going to end up staying with the 406 size wheel. There just doesn't seem like a big enough improvement compared to cost to jump to the 451s. However, I do have a wider rim and was wondering if anyone has suggestions for either prebuilt wheels or narrower rims that would allow me to use Swalbe Stelvios or the skinny Contis. I am interested in lighter rotating mass and skinnier tires..I still want to make my Raleigh Twenty faster!!!