I've ordered a frameset from Black Mountain Cycles, a rando type 650B bike. Mike Varley designed this frameset around 47mm tires on 650B wheels.

Is there a general guideline for the distance between inner walls of rims for this type of setup?

Not sure how much riding habits, rolling surfaces, tire pressure, my age or other factors may figure in. I'm 66, certainly not an aggressive taker of corners and I'd be rolling on 70% pavement and 30% fine gravel or clay roads. I'd value comfort and stability over and above cornering ability and quickness.

Do I need a wider or narrower rim platform? Are there minimum or maximum limits wise to observe?

Thanks for any tips!

bob