November 1, 2009 1:36 PM PST
The reason for a 21" wheel, besides cool looks, is it will handle pot holes better because of the larger radius and for the same reason improved gyro characteristics helps you maintain better handling stability in corners. If you are going to go that rout, the wider rim and tire is what I would suggest. A single brake will work just fine as long as you use quality components and keep the air out of the lines. Steel braided lines also give a more positive response and last longer than rubber lines.
November 17, 2009 11:06 AM PST
All 1200 Sportster Custom's have a 21" Front Wheel with a single disc
They have been doing this for years... without any problems
November 17, 2009 12:04 PM PST
Yeah man I'm running a 2006 Springer Soft Tail with a 21" spoke front wheel. Braking is good but rim is easy to warp...I've warped two already in three years on small pot holes.
November 22, 2009 12:22 AM PST
Runnin a 21" on my Ground Pounder with PM controls and calipers. No problems.