It is certainly possible on a Wisper, I now have 60-559 Big apples fitted under my full length SKS (I think) 60mm mudguards. It's a very tight fit with 1mm clearance in places but it still works at the maximum pressure of 60psi.today when i was breakfasting a baloon-bike with big-apples drove by..
it had 26" and 60er tieres as mine..
AND: it had metal mudguards
looks like it was the way it came out of the factory so no home-made mudguards
so its not impossible
I've only done about 30 miles on it so far and it feels like a big improvement, no apparent loss of speed and the road surface feels smoother. An added advantage is that it feels more 'planted' and gives more confidence in the corners, I think I'll enjoy this tyre.
