Here's a great idea for those of you with tires with large, flat lugs such as most mud-terrain style tires and Swampers. Those big lugs might be great for some things, but the lack of siping or grooves in those tread blocks means that your traction will be less than great on wet roads or on ice.

Siping the tires is a great way to get better rain, snow and ice performance out of your tires while adding more biting edges for traction in the rocks and a cooler running tire tread (i.e. more tread life).

Many tire shops will sipe your tires for you, but it can also be done for free if you've got a utility knife and a couple of free hours. The idea is to put slits across the tread that will open up when under pressure and present more biting edges. There a couple of guidelines to follow:

1. Don't make the sipes any more than 1/4" deep

2. Place the sipes 1/4" apart but keep them around 1/2" from the leading and trailing edges of the lugs to help reduce chunking of the tread.

3. Only sipe the inner lugs to also minimize chunking of the tread.

Although in the picture above the sipes do not look like much, you can feel a difference by just running your finger down the tread. The harder you push down while moving down the tread, the more resistance the sipes have. Although not a very scientific test, I placed a piece of 2x4 across the tread before and after I siped the tire. In both cases, I leaned on the board with one hand and moved the board with the other. There was a big difference in the amount of resistance.

UPDATE:

Wow! After taking the newly siped Swampers off-road, I can immediately tell the difference in traction. The sipes act as wipers and clean off dirt covered rocks so that there is more grip for the lugs. Also, the sipes have opened up more now that I have gone on a few trips with them. Finally, I have not seen any chunking of the tread so all is well!