With that bike and your size, the only way I’d go to to a 650b is if you ride lots of tough single track. 700c has an advantage in rollover and rolling resistance. As far as tire width choices, I’ll throw some opinion out there...
1. Larger volume tires can really help the rider if they are big/heavy and/or they are frequently riding on soft or loose surfaces...or really rough stuff like large crushed rock, large diameter gravel. They also cost you in wind, weight and rolling resistance if you plan to go faster or be competitive.
2. Smaller volume tires are faster and less forgiving.
3. What is a larger volume tire? Pretty subjective. If you weigh 140 lbs, a 38 or 40mm tire can be all you would ever need in tough conditions and a 35mm on race day. If you weigh 240, a 45mm tire or larger is pretty forgiving.
I think the 700c 45mm is the ideal tire for our conditions and my size (240) but I usually swap it out for a 38mm when it’s gravel race day.
Oh, and this is tubeless only we’re talking about here...
Last edited by pipeliner; 04-27-21 at 03:22 PM.