The Sportster 19" wheel has the spoke holes going around the hub in a circle. The 21" Sportster hub has the spoke holes going around in a zig zag pattern. Does anyone know why they decided to drill the hubs differently?

 

What year are the wheels?

 

These are pics from a 2010, 1200 Custom and a 1200 Low. The trend in hub differences goes back as far as 2002 (pics from Total Motorcycle.com).

19" HUB


21" HUB

 

I've never noticed but my 19's are round and my 21's are staggered like the pics. I'm also curious as to why.

 

I can almost guarantee it has to do with the different requirements for support of the spokes. Spokes work great in tension, and only in tension. The different size, as well as a narrower design on the 21'', probably require different patterns on the hub to successfully reduce the stresses due to their differences in size. My suspicion is the width is the big factor that affects the geometry and the reason why they're different.

 

I had a bit of concern as I am lacing my 19" Dyna hub to a 21" Sportster rim and spokes. The part numbers for the DYna and XL 19" rim and spokes are the same...so I assumed the 21" would work well...then I noticed the spoke hole pattern. Though, quite a few of the 21" rims at JP Cycles with a similar hub, have the regular holes as on the 19" (not staggered). So was the staggering really necessary?

 

It's HD. Dont ask why.