I putting a Stieb S-501 sidecar on my '63 R69S and I've put a 26/6 gear set in the final drive as per the manual, but I've read that unless I'm riding with a passenger in hilly country 26/6 might be a bit low. I'm on the hunt for a 27/7 gear set and it's proving a elusive bugger.

I think they only made 3, at least it feels like that.