On Friday, April 12, 2019 at 9:27:51 AM UTC-5, db wrote:
My son is set on getting a belt drive for the bike he
is building. What is good about them? You have to have
the exact length for your bike, and if it breaks, it
is very expensive to replace.

So, why?

--
Dieter Britz

Go over to YouTube and do a search on Gates Belt Drive. A number of videos will appear that talks about bikes with this drive system and usually Rohloff or Pinion gear boxes.