I have converted a 2008 Custom to a trike and am looking at my options for the front wheel and tyre.

I am committed to the narrow glide of 7" as that is the size of the trees I have and also the front mudguard (fender) has been custom painted.

I want to convert from a 21" to a 19" front cast wheel and I think I would be better with the 110/90-19 tyre. I think I know as standard the Sportster 19 cast wheels have a rim width is 2.15" but there is a ThunderStar rim for example that is 2.5" wide.

Do I have any other options HD or otherwise for a 19 x 2.5 wheel?

The difference in tyre sizes is:
80/90-21 --- 110/90-19 --- 100/90-19
Diameter inches (mm)
26.67 (677.4) --- 26.8 (680.6) --- 26.09 (662.6)
Width inches (mm)
3.15 (80) --- 4.33 (110) --- 3.94 (100)
Circum. inches (mm)
83.78 (2128.11) --- 84.18 (2138.17) --- 81.95 (2081.62)
Sidewall Height inches (mm)
2.83 (72) --- 3.9 (99) --- 3.54 (90)

I have seen I could put the 110/90-19 on a 2.15" rim but the recommended size rim is 2.5".
https://thisiscasperslife.files.word...size_chart.pdf

What is the downside to using the 2.15" rim width?

 

I had my 215 wheel relaced with a 2.50. Just looks better to me.

 

There are 19" x 3.5" wheels used on some recent Touring models with a 130/60 tyre, which would make a great front wheel for a trike. That probably represents the widest you can possibly go to, however I am not sure if one of those wheels will fit into your forks. Certainly a 2.5" wide rim with a 110 tyre on it sounds like a good solution.