Some modern wide tyres might have to be deflated before they will fit between the cantilever brake blocks. My tyres are not that wide, and they were a tight squeeze. This problem may be worse when using the more modern cartridge style of brake blocks with replaceable inserts, as they are slightly longer than the old style, and can foul on the fork legs and seat stay tubes when the straddle wire is released. In my case I can't revert to old style short brake blocks, because I have ceramic rims, so I need Swiss Stop blue pads. I had to abandon my plans to fit wider tyres when I realised that as well as brake block clearance being a problem, there would be little or no clearance between the tyre and the frame/forks. Fortunately maximum tyre performance is not a big deal for me. I like bumbling along bridleways rather than shredding downhills at trail centres.