So you made the jump to winter tires a couple seasons back and saw the proverbial light. Fantastic. I'm sure experiencing the added traction and safety these past winters has you singing the praises of your winter tire of choice. However, are they up to the task for this coming season?
Winter tires have three main components that contribute to their glorious traction. Tread compound, tread design, and tread depth. Depending on the specific driving conditions you see in the winter time, you might be past the optimal tread depth.
Below 6/32nds of an inch of tread depth you'll see a drop in winter time traction. This applies to all tires, not just winter tires, so even if you have all season tires it may be time to go take a look at them. A tread depth gauge like the Dill Digital Tread Depth Gauge shown here to measure 6/32" is best; but there are other ways to check depth.
You may have heard of the Penny Test where you use the top of Lincoln's head on a penny to see if your tires are legally worn out (2/32"). If you flip the penny around and insert into various spots on the tire with Mr. Lincoln's memorial upside down, you can measure 6/32". The roof of the memorial is at 6/32" so if it's sufficiently covered, you have more than 6/32".
However if you have snow tires, manufacturers have made it even easier to check for 6/32". They have built in snow platforms molded in at 6/32", reinforcing the importance of tread depth for winter time traction. These are raised blocks of rubber in the circumferential grooves, and when they become level with the top of the tread blocks the tire's tread is at 6/32". You may find two sizes of these blocks in the tread as there might be the typical tread wear indicators molded in at the legal 2/32". If you are at this platform or it seems the tire has worn down into the platform, your tires will not be performing at their best. They still may be good but keep in mind they won't be as good as the first few seasons. Assuming you still have some tread to go before you get to the snow platform your tires should be up to the task this winter.