From Progressive:
"Lots of you Bagger guys swapping to 21″ front wheels, we love the look, too and are quite often asked what should be done to the front suspension once the taller wheel is installed.
The HD Touring model chassis is not a fan of the additional rake the tall wheel creates and will feel floppy (wants to fall into turns), es…pecially at slow speeds.
We recommend lowering the forks 1 inch (two if you are riding a Street Glide or have installed lowered rear shocks) to level the bike out. The cost is nominal ($129 for Drop in style lowering kit) and you’ll find that once leveled out, combined with the new rubber up front, the machine will handle nicer than stock (it really is just a giant sportbike tire!)."
SERG's are lowered, so youze'll need to figure the geometry out based on the setup. But they make sense here regarding the geometry change that putting the 21" on makes. Something to ponder!

Hoist!
