This may be one of the more severe cases - a front Weirwolf 26x2.1 and a Maxxis Detonator 26x1.25. I bought the detonator (cheapest tire in the shop) for use on a trainer, fully intending to get another rim for the rear Weirwolf.

However did some very light off-roading with the rear Maxxis wheel (mainly long grass, gravel, packed dirt and mud) and it worked surprisingly well. Felt quick and nimble enough yet stable.

So far it feels good and even my friend is contemplating doing it, but is this going to bite me in the butt some time in the future?