A general rule of thumb for determining internal width of hook bead rims when only external width is given is to subtract 5mm from the external width.
I am running a pair of 25mm Schwalbe Stelvio Plus tires on Dyad rims with no problems so far. The Stelvio Plus is a tire which, at least on the Dyads, is slightly wider than the liste ETRTO width. I would not want to go any narrower.
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Gear Hubs Owned: Rohloff disc brake, SRAM iM9 disc brake, SRAM P5 freewheel, Sachs Torpedo 3 speed freewheel, NuVinci CVT, Shimano Alfine SG S-501, Sturmey Archer S5-2 Alloy. Other: 83 Colnago Super Record, Univega Via De Oro
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