You’ve got a picture of a bike with an actual tyre in and the clearance available, is that enough clearance for you?
If you’re asking a framebuilder/manufacturer for their recommendations, they’ll be cautious, because there’s a huge amount that can affect whether a tyre is too big for a frame:
– How much mud are you riding in? dry hardpack only – you can get away with bigger tyres and less clearance.
– One company’s 42c is another’s 47c.
– From one 42c to another – one might be perfectly rounded with low knobs, the other might be squarer with wide shoulder knobs. the widest point on the latter tyre will be higher in the stays and reduce clearance.
– Rim width will change the actual width and the actual profile of the tyre when it’s mounted.
– Differences in rider weight, riding style and wheel stiffness will affect how much a wheel deflects in the frame, and how much clearance is taken up by that deflection.
– Some riders will be horrified at paint rub, others won’t care.
If you’ve got tyres in mind, google “measured width calipers shoulder knobs casing [ your tyre here ]” and have a think about how much clearance that leaves and whether that’s enough for you given all that^.