Good day to you guys. I have this custom made steel gravel bike that currently has 700x35c tires on. I am planning on converting the wheelset to a 650b particularly the 650b WTB Horizon 47c. I have no problem with the fork since I know for a fact that it has a lot of clearance. But the frame builder told me that the max tire capacity of this frame is 700x38c but I figured that was just a conservative estimate since I already have successfully tried fitting a 700x41c Surly Knards in it but with very little room to spare.

The reason why I want to switch to 650b is because I find that the standover height of the bike is a little too tall for me and a mechanic told me that switching to 650b would reduce the standover height. None of my mates currently have a 650b wheels so fitting one at the moment is not doable.


Here are pictures of my seatstays and chainstays. The clearance for both stays is approximately
53mm.




Obviously, 53mm > 47mm but apparently, some tire measurements aren’t accurate at all. Was wondering if the WTBs is one of those tires. Am I able to fit 650bx47c in this bike? If no, what would be the thickest 650b tire that I can fit in this bike. Thank you all for your help. Much appreciated