Originally Posted by
Cynikal
With boost, the BB shell is wider, thus the spindle, so you avoid the crank conflicts with the stays. This with the wider rear end allows for additional tire clearance.
I've been in the same decision loop that you are in about a future build. I'd like a mixed terrain tourer but the tire/crank clearance issue kept coming up. I currently only know how to build with lugs. The best way through this that I've come up with is to use disk brakes and two different wheel sets. One 650B with a 2.1 and a 700c with 38's. Both are close in overall diameter (702 mm vs 706 mm). I know this does't meet your need to use your existing wheels but it's where I've landed.
As far as I know, which may not be very far, the BB maybe wider but the outside dimension of the BB with bearings is the same, I think around 95mm.
You can get what you are looking for using lugs and a prefabbed disc caliper mount/dropout with a mtb/gravel crankset, wider q-factor and can use a small BCD allowing for smaller chainrings, see picks above of my white frame, I am in the process of finishing a frame that will fit GRX 46/30 and up to a 2.2 inch 29er tire. Before the gravel boom, the fit issue for the cranks has been finding a non-square taper 2x crank that will fit a 46/30 as MTBs all went to 1x. I don't know if the latest frame will fit a 48 tooth or not without crimping the chainstay.
There are other options beside GRX but to me the price gets prohibitive. The White crankset on the linked bike is $500+ GRX is under a $100.
Still mullets are pretty cool.
