MountainCruiser

Is anyone here running a 650b wheelset? What tire pressure are you running?

B. Carfree

It depends on the width of the tires (wider tires means lower pressure), the weight of the team (heavier team means higher pressure to keep the sidewall from deforming too much).

In spite of how it feels and the results of unrealistic drum tests, lower pressures apparently lower suspension losses, and thus roll faster. It feels slower because you lose those high frequency vibrations (actually, that's a good thing).

Kontact 

Rolling resistance is the least at the optimal tire pressure. If you go too low the rolling resistance increases AND you're going to get a pinch flat.

Find one of the tire pressure charts that use bike/rider weight vs tire width.

OneIsAllYouNeed

We run a whole bunch of 650b tire sizes on our tandem. Pressures range from 35psi to 75psi depending on the tire width and load. For example, we used from 52mm tires at 50psi this weekend. We ran 57mm tires at 40psi for a recent gravel race. Our normal road tires are 42mm at 70psi. Typical team weight (including bike and luggage) for us is around 320lb.

MountainCruiser

We are running 650b x 47 WTB Byways. Team weight closer to 400, have both put on too much weight so that # should be dropping. Considering going tubeless. I have never ran tubeless on my road bikes but have ran tubeless on my Mtn bike for quite a while and have been very happy with it. We are new to the tandem so I'm just trying to get a feel for how I need to set it up.

OneIsAllYouNeed

You're up against the pressure limit on Byways. IIRC, the sidewall says 50psi max. We sometimes use the Byway at 50psi on our tandem. Optimally, you'd be running 65psi in them at 47 to 48mm width. The closest tires with higher pressure ratings are the Schwalbe Big Ben 50mm, Schwalble Marathon Almotion 50mm, and Schwalbe Marathon Mondial 50mm. I haven't used those tires, however.

Does your frame have clearance for Schwalbe G-One (Big One) 2.35" (60mm)? It's a really fast-rolling, comfortable tire with plenty of load capacity.

Personally, I wouldn't bother setting them up tubeless. The risk of tires blowing off is greater without tubes installed.

MountainCruiser

Those tires sound interesting! I believe that I have enough clearance. Might have to give them a try in the future.

akexpress 

We run WTB byways on our adventure tandem at 50psi tubeless on 35mm carbon rims with no issues.
these are used on gravel , rail trials and pavement. When loaded for touring total weight is about 400#. They roll nicely and tubeless has been trouble free. YRMV