Dear All
In relation to tyre pressures in my 1926EW, personally I am now running about 40 psi. This is after previously running 25psi on a rally at Dubbo NSW and cutting the valves off two tubes (rear wheel) when the 26x3 beaded edge rear tyre rotated on the rim at this pressure. It can go down awfull quick when this happens.
On advice from others at this pre 39 rally, I increased the pressure to 40 psi and didnt have a problem after that.
However another friend on a 23 CW runs the same size tyres at a lower pressure - however the brand of tyre and origin is different (mine are new and made in Vietnam and his are older from Japan) and his rims are in rougher condition (mine had just been illmenite blasted and repainted). On this basis it may be that the BE profile of some makes of BE tyres is slightly different to that of the rim and other makes of tyres or it may be even the mounding lubricant on newer tyres or the paint and condition of the rim. You have to take into account that most of the 26x3 BE tyres available (for us in Australia anyway) are from asia and are used for hand driven push carts and motorized 3 wheelers - the quality and the profile may not be what it was in 1926 or so.
On the basis of my direct experience, I will be running 40 psi to ensure that the beaded edge of the tyre is really bedded into the rim, it is really disconcerting losing the rear tire when in a corner, which happened when I was trial running the bike at work, in front of a heap of my employees (earning me the nickname 'Buster' after the crash test dummy on Mythbusters). The second time, at the rally (which Ian also attended) was at least in a straight line and not nearly as dramatic (quite stately actually - however, as Ian will attest to, it may have been the copius amount of oil from the incorrectly connected oiling system - which started another forum topic - that assisted the 'slip' of the tyre on this occasion).
Overall I would run 40 psi however, if you decide to run less, perhaps if they are new tyres, ensure any coating from the manufacture process has been removed from the beaded edge.
Another tip given to me at the Dubbo rally, was to leave the locking nut on the valve stem loose by 5mm or so - then if the tyre is starting to rotate, you have a chance on inspection after a short run (and after each run thereafter) to pick up if the valve stem has been pushed over (indicating the tyre is rotating ever so slightly less than your rim - which is not a good thing). This allows you to deflate the tyre a bit, kick it back around so the valve is square again and FULLY reinflate to a higher pressure - all before it goes far enough to actually cut the valve off.
Hope the above assists and prevents you from potentially scratching a (probably) newly restored bike. The other option is to position yourself (quickly) between the bike and the road, as I successfully did at work when I cut the valve off the first time (and thought it was a faulty tube).
Since running at 40 psi I didnt have a problem, I just sheared a magneto shaft instead.
Best Regards
Derek