Vintage Raleigh Criterium roadbike suitable for touring and wider tires?

Hi, I bought a Raleigh Criterium roadbike (dating from the eightees) one and a half year ago and converted it to 650B in order to fit wider tires. At the moment I use 32mm wide tires (they measure 33mm wide). I would like to fit wider tires for more comfort and maybe for future bike trips and I'm wondering if 38mm wide tires would fit. I made a few photos to show clearance with the current tires. If I measure the space between the chainstays at the widest position of the current tire, I measure 40 mm. I've read about 38x650B tires that measure a bit more like 40mm, so I'm not sure if this woudl be a good plan? Or would wider tires mean a different bike (frame)?



chainstay clearance @ 32x650B (33mm measured width)


rear wheel


front wheel (photo is upside down)