Originally Posted by Wavshrdr
As much as rim size will have an effect on handling, tire choice will likely even have a great effect. I personally like the 406 size just for the shear number of tire choices available in this size. Keep in mind that a tire and rim combination that looks fast (tall and skinny) may not be as fast as something like a Big Apple setup especially on rough roads. If you just wanted to build a track type bike then a 451 with a Stelvios might be the way to go if you are riding on pretty smooth ground.
This jibes with my experience: if you want to run narrow, high-pressure tires, you'll generally get better handling with the larger diameter. But you can get even better handling, and comparable (or better!) performance, with a wider tire in the smaller size.
The 50-406 Big Apples are only a few mm smaller in overall diameter than 28-451 Stelvios, but they improve handling and shock absorbtion dramatically.
Try some
well-constructed wide tires on your Swift before switching to 451s.