Originally Posted by
heidelbergensis
<snip> I wanted to fit modern wide tires <snip>
The clearances are pretty tight <snip> the dimples on the inside of the chainstays are placed well back of where a 700c tire would hit
Yeah this bike is a prime candidate for 650b conversion IMHO. Having the chainstay indents in the wrong place would bug me to no end.
For measuring before building wheels, you can't beat a
Rossman gauge. $25 might sound like a lot for a couple pieces of laser-cut plastic, but it can save you a lot of money compared to buying 650b wheels!
Here's a review of the Rossman gauge by Jim Langley.
https://www.roadbikerider.com/hahn-r...rance-checker/
A tape measure and some cheap plastic measuring calipers can also suffice, if you know the numbers for where the 650b tire will end up relative to the dropouts. (I don't know off the top of my head but could measure for you if needed.) Measure the radius to the widest point on whatever tire you want to use, and make a temporary mark there on the chainstay, then measure the width there with calipers. Use the overal radius to the top of the tire for checking clearance under the crown and bridge, but that will almost certainly be fine. I think the width between the chainstays will be your only worry. You almost never have to worry about the BB height being too low as long as you can fit some decently-large tires, preferably 40-42 mm but at least 38 mm.
If the c-stays are still too narrow, even back at the 650b radius, then these stays can be indented more (and further forward), but sometimes that mod is more involved than the bike owner is willing to go. Unless you're willing to make your own indenter, it'll likely require you to send the frame to one of the artisans who's set up to do this, like BF's own
gugie . But again IMHO, this frame is worthy of that much customization to make it even that much cooler and more practical (not to mention more comfortable).
My own stay indenter was sort of a testing prototype, it worked great but I built it too cheaply, with a garbage-quality Chinese C-clamp, and the threads are feeling rough like they're self-destructing, so I'm not currently set up to be able to offer this as a service. I will make a strong one at some point, hopefully by this Spring, but don't wait for me, there are people who can do it right now.
Mark B