I was going to order a new 21" rim for my Softail today but then got thinking about going with a 19" rim. I have previously put 2" under tubes on so I'm not sure if I'll have clearance problems.
Any thoughts on this conversion?

 

misunderstood... deleted

 

16", 19", and 21" wheels all have about the same outer diameter when tire is installed.

 

The hub if a 19" wheel is significantly narrower than the hub of a 21" wheel so you're gonna need to space out the rotor and figure out your spacers.

 

My plan was to have a rim laced onto my hub.

 

You won't gain anything by doing that as the 19's and 21's are virtually identical after tires are installed.
The main difference is the 19's have a bit taller sidewall than the 21's.

 

I was thinking the 19" might be less of a "crack follower'

 

Maybe a little bit but you'd need to run a 16" to get a substantial difference IMO.

 

To avoid your crack habit, all you need is a tire that doesn't have longitudinal tread patterns. Some brands do better than others. Not trying to talk you out of the 19", because it just may improve your ride. Let us know.

 

Don't think you'll lose much. My 21"er with a MH90-21 three is 26 1/2” in diameter and my 19"er with a 120/70-19 tire is 26 ". So your only looking at a 1/2 loss going too a 19 caused of the side wall of the tire...