i think the OP has the minimum inside width mixed up with the outside width. rhyno lite rim dimensions, i think , are: inside = 20.7 outside width 27.5. the chart above refers to the inside width. if so the OP shouldn't have any trouble with a 1.25 tire. IME, i've never seen a MTB rim that wouldn't except a 1.25 or wider tire. not that i would be surprised or disappointed if somebody posted a few pics of some just to prove me wrong.
(i know i wouldn't hesitate for a second.)
here's the specs that i found:
[TABLE="class: spectable"]
[TR]
[TD="class: spechdrs"]Rim ID[/TD]
[TD="class: specvals"]181[/TD]
[TD="class: specvouch"][/TD]
[/TR]
[TR="class: trgray"]
[TD="class: spechdrs"]Manufacturer[/TD]
[TD="class: specvals"]
Sun[/TD]
[TD="class: specvouch"][/TD]
[/TR]
[TR]
[TD="class: spechdrs"]Model[/TD]
[TD="class: specvals"]Rhyno Lite[/TD]
[TD="class: specvouch"][/TD]
[/TR]
[TR="class: trgray"]
[TD="class: spechdrs"]Descriptor[/TD]
[TD="class: specvals"](pinned)[/TD]
[TD="class: specvouch"][/TD]
[/TR]
[TR]
[TD="class: spechdrs"]Tire Size[/TD]
[TD="class: specvals"]ISO 559 (26" mtn)[/TD]
[TD="class: specvouch"][/TD]
[/TR]
[TR="class: trgray"]
[TD="class: spechdrs"]ERD[/TD]
[TD="class: specvals"]548.8 mm[/TD]
[TD="class: specvouch"]0[/TD]
[/TR]
[TR]
[TD="class: spechdrs"]Offset drilling[/TD]
[TD="class: specvals"][/TD]
[TD="class: specvouch"]0 L, 0 R[/TD]
[/TR]
[TR="class: trgray"]
[TD="class: spechdrs"]Outer width[/TD]
[TD="class: specvals"]27.5 mm[/TD]
[TD="class: specvouch"][/TD]
[/TR]
[TR]
[TD="class: spechdrs"]Inner width[/TD]
[TD="class: specvals"]20.7 mm[/TD]
[TD="class: specvouch"][/TD]
[/TR]
[TR="class: trgray"]
[TD="class: spechdrs"]Overall height[/TD]
[TD="class: specvals"]15.5 mm[/TD]
[TD="class: specvouch"]v[/TD]
[/TR]
[TR]
[TD="class: spechdrs"]Brake wall height[/TD]
[TD="class: specvals"]12.6 mm[/TD]
[TD="class: specvouch"]v[/TD]
[/TR]
[TR="class: trgray"]
[TD="class: spechdrs"]TireType[/TD]
[TD="class: specvals"]clincher[/TD]
[TD="class: specvouch"]v[/TD]
[/TR]
[TR]
[TD="class: spechdrs"]JointType[/TD]
[TD="class: specvals"]Pinned[/TD]
[TD="class: specvouch"]v[/TD]
[/TR]
[TR="class: trgray"]
[TD="class: spechdrs"]Eyelet type[/TD]
[TD="class: specvals"]Single[/TD]
[TD="class: specvouch"]v[/TD]
[/TR]
[TR]
[TD="class: spechdrs"]Weight[/TD]
[TD="class: specvals"]550 g[/TD]
[TD="class: specvouch"]v[/TD]
[/TR]
[TR="class: trgray"]
[TD="class: spechdrs"]URL[/TD]
[TD="class: specvals"][/TD]
[TD="class: specvouch"][/TD]
[/TR]
[/TABLE]