If you want good traction on slippery stuff, here are some options:
1) Buy a Michelin X-11 trials tire - they stick like glue, on greasy clay, roots, wet rocks, snow covered rocks - anything slippery and slimey. The only downside is that they don't work so well in deep snow. [Cost $120]
2) Go to your local hardware store and buy some sheet metal screws with the hex heads and screw them in your knobs. This works better than the trials tire in the deep snow. They do not work well on rocks. [Cost $5]
I have also had a regular knobby tire studded by a tire shop. I was underwhelmed. The trials tire outperformed it everywhere.
For my winter riding, light snow (<4 inches), ice, rocks, greasy mud, slime and slop the Michelin X-11 trials tire absolutely BLOWS everything else away (including Dunlop 756 & 739, Michelin S-12 & H-12, Bridgestone ED-78 and the IRC iX05H nobbies). It sticks so well you will not believe it. :eek:
Eric K
'01 GasGas 300XC