Whoops, seems like they went to the wrong shelf on that one!
I'm really curious about this bike, or Tantan FM301 or whichever. When you get the chance it would be interesting to see the actual max tire clearance.
Looks like it could be the ultimate allrounder if you could squeeze in a pair of 40mm gravel tires, very sporty rear at 410mm chainstays!
I have the LT268, it's rated 32C, i run 32C at the rear on a 34mm rim, so it measures 33.5mm, and i have PLENTY of clearance, front and rear, so i'm pretty sure i could run 34 or 35C (slick). When i bought the frames, i remember Alisa sent me cad drawings with the actual clearance on the frame, so if you're considering buying a 301, you could ask her for the same.
I'd bear in mind that if you want to put knobby gravel tyres, you should account for mud, crap, stones and what not in the clearance, so you'd probably be asking for trouble.
If you want a road oriented gravel bike, i can say good things, from 1st hand experience, of Xiamen carbon speed's grevil clone. Peter is on the forum. It clears 50C, but compared to my other gravel bike, it's much more road oriented / capable. And pinarello does know a thing or 2 about bike geometry, and clearly markets the grevil as a speed machine, not an adventure / bike packing horse.
