So here's a fresh data point - I just went out to my trike and measured the right front 40-406 Marathon GG. It's 1.54 in wide on my dial caliper, which is 38.5 mm. I've got no idea though what the rim width is, other than it's about right, nor what the pressure is today, since I haven't done that in 2 weeks at least.
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Genesis 49:16-17
"Well, well!" said Holmes, impatiently. "A good cyclist does not need a high road. The moor is intersected with paths and the moon is at the full."