Join Date: Nov 2014
Location: Eugene, Oregon, USA
Mentioned: 6 Post(s)
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I don't have the frame. Maybe someone can measure the fork width, chainstay, and seatstay clearances.
As far as BB clearance.
650b is 584mm
26" is 559mm.
Or, 25mm difference. Half that (radius) is 12.5mm.
Surly sells the Straggler with 650x41 tires.
I would expect the bike to also be fine with 650b x 1.5" (38mm) tires.
So, say you go with a 50mm tire, the profile will be about 9mm taller, and 4.5mm wider (each side) than stock.
So, going to (FULLY INFLATED) 26"x50mm, your BB drop should be about 3.5mm, or about exactly the same as going with the 650b x 38mm tires.
Less drop with wider/taller tires. So, a 26x2.2 (55mm) would be slightly taller than the 650bx41.
The difference, of course, is that if you run them at low pressure, the BB may actually sit a little lower, or bounce lower when riding.
I saw a note that the Straggler had a 72mm bottom bracket drop, slightly more (lower) than the typical 26" (61mm?), but you're wanting to run awfully large tires.
Going with disc brakes, you don't have to worry about cantilever brakes fitting.