Traction and Patterns

How do patterns on tires increase tire traction? Looking for a primer on traction here.

They don’t, that’s why race cars run slicks. Maximum traction. The tread pattern is to channel standing water.

Then why do hiking boots have traction patterns?

Soft dirt, the lugs dig in, just like an off-road tire. I thought you were talking about street tires.

Also, the boot sole is flexible and contours to the rock a bit and the rubber is softer than tire rubber, giving more grip.

I was, but now I’ve realized that the same principles don’t seem to apply to everything that uses rubber for traction!

Yes, under ideal conditions a slick offers the most ‘contact patch’, the largest area of tire meeting the road.

But highways are not race tracks and some compromises are needed. The tread needs to channel water away from the surface of the contact patch and also allow for cleaning of the tire treads. And for performance they need to grip the road when dry too.

Directional tires are typically used on performance cars to meet this compromise of contact and weather. I run Toyo Proxes 4 on my muscle car. In the image in the link you can see the arrow shaped segments on the interior tread. These point in the direction of the rotation of the wheel.

Under acceleration the space between the arrow shapes becomes smaller and the tire acts more like a slick, with a larger contact patch. Under normal driving the gap remains open and allows for clearing of water.

https://www.google.com/search?q=toyo+proxes+4&hl=en&tbm=isch&tbo=u&source=univ&sa=X&ei=KbkpUYRbgtOtAZD_gPAJ&sqi=2&ved=0CHAQsAQ&biw=1920&bih=934#imgrc=oM7jvFrOytDSbM%3A%3B1RL9z9lSKXHZ_M%3Bhttp%3A%2F%2Fi206.photobucket.com%2Falbums%2Fbb48%2Fbumblevr6%2FIMG_20120428_160748.jpg%3Bhttp%3A%2F%2Fforums.vwvortex.com%2Fshowthread.php%3F5672331-(1)-Toyo-Proxes-4-215-40-17-75-Tread-Left-50-L.I.N.Y.-Pick-Up-Only%3B1024%3B768

Often the the pattern is made to be self cleaning when in snow or mud. An agricultural tractor tire is a good example of this.

http://gencotyre.en.alibaba.com/product/565092039-200676788/Agricultural_font_b_tractor_b_font_tires_14_9_28_7_5_16.html

The tread pattern has become a branding design to differentiate one product from another. Sort of like the pattern on the back pocket of jeans. There isn’t a huge difference between most tires in traction and rain channeling abilities despite the many designs.

Up through the Fifties, most all-weather auto tires just had a series of zigzag patterns around the circumference and one manufacturer might vary the width of the tread blocks between the grooves to make their tire look different. I’m guessing that the intricate designs were not possible until the introduction of better molding tools.

I remember an episode of Top Gear in which Hammond has difficulty driving an F1 car because he can’t get it up to the 100+ MPH quickly enough for the racing slicks to gain traction. He ended up having to quit because he couldn’t gain traction before reaching the first turn as I recall. I’m guessing that’s also why I see cars burning rubber before a drag race (?). I did not know that heat played such an important role in traction – at least in racing.