Lost the pic but I saw a bike set up by someone for their commute. Knobbly tyred MTB and to get grip- he had put Zip Ties round the rim and tyre. I don't know if it worked but looked as though it would. And it was an old trick we used in the Marines on mud- we used 1" thick rope to give grip and it worked. Bit messy putting the rope through the wheel and tyre but it just gave that bit extra to get through deep mud.