Different width tyres
By CyclingUKvolunteer
Edward Holt
The obvious place to put a fatter tyre, if using two different sizes, would indeed be at the back, since bicycle weight distribution is heavily biased to the rear. That said, the advantages to running a fatter front tyre, in terms of grip and comfort, are not negated by having a narrower rear and it can be argued that, if more of either is needed, it is more useful at the front end. After all, hardtail mountain bikes with a suspension fork are a commonplace, unlike the alternative arrangement.
Richard Hallett
Cycle’s Technical Editor