Keep an eye on your tires' tread depth

[mbeige]

A good read considering it's the rainy season na. Be safe out there.

Read it all: http://www.tirerack.com/tires/tests/...ay.jsp?ttid=85

Stopping a Car

Even though the speed to begin braking the 3,400-pound BMW sedan was 20 mph higher than the 50-0 mph braking tests we conduct at The Tire Rack, the braking forces developed by the new tires felt reminiscent of full tread depth tires we've experienced on our home track. The car pitched forward as the brakes were applied, quickly took a set and slowed the car with authority. After repeated runs we learned that the average stopping distance for the new tires from 70 mph was 195.2-feet in 3.7-seconds.

Testing tires with the 2/32-inch minimum legal tread depth taught us the probable origin of the driver's accident report statement, "I hit the brakes hard, but nothing happened." There was a perceptible delay while waiting for the braking forces to grow after initiating the stop. Looking at the graphs recorded by the DriftBox confirmed this discomforting situation when we realized we were still traveling at about 55 mph on the tires with 2/32-inch of remaining tread depth when we reached the same distance it took the new tires to bring the BMW to a complete stop! This time the repeated runs taught us that the average stopping distance for the still legal 2/32-inch deep treaded tires from 70 mph had almost doubled to 378.8-feet and took 5.9 agonizing seconds to accomplish. We had the same car and the same brakes, but the tires with minimum legal tread depths weren't able to generate enough traction on the wet road to bring us to a quicker stop.

Stopping a Truck


Then we turned our attention to the approximate 4,500-pound Ford F-150 Super Cab 4x2 pickup. While we expected its additional 1,100 pounds of curb weight to help push the tires down through the water to the road, we felt that the energy required to stop the extra weight would increase braking distances. As with the BMW, we accelerated to the 70 mph target speed on dry road and drove across about 75 feet of wet road before hitting the brakes to begin our panic stop.
While not experiencing as much absolute braking force, the pickup pitched forward a bit more than the car when the brakes were applied, took a set and slowed a bit more leisurely. We learned that the average stopping distance for the pickup on new tires from 70 mph was 255.9-feet in 4.8-seconds.


Testing tires with 2/32-inch of remaining tread depth on the pickup further emphasized the driver's accident report exclaiming, "nothing happened" when they hit the brakes. There was a noticeable hesitation waiting for the braking forces to grow after initiating the stop. Looking at the graphs recorded by the DriftBox showed we initially only slowed 12 mph on the tires with 2/32-inch of remaining tread depth when we reached the same distance at which the new tires brought the F-150 to a complete stop! This time the repeated runs taught us that the average stopping distance for the legal 2/32-inch deep tires from 70 mph was a staggering 499.5-feet in 7.5 excruciating seconds. In addition to the hydroplaning risks associated with shallow treaded tires, this means that the highway would have to be clear for almost 1/10 of a mile ahead of the pickup to allow this combination to complete a panic stop without hitting something.


Stopping with the partially worn tires with 4/32-inch of remaining tread depth again confirmed that the initial stopping forces again felt more like the 2/32-inch deep tires than new tires. Looking at the graphs recorded by the DriftBox showed an improved, but disquieting situation since we were still traveling about 47 mph on tires with 4/32-inch of remaining tread depth when we reached the distance it had taken the new tires to bring the pickup to a complete stop! The runs indicated that the average stopping distance for the 4/32-inch deep worn tires was 377.8-feet in 6.0 seconds, again splitting the difference between the new tires and those that had legal minimum tread depths.