Truck tire testing update: Measuring the slippery reality of hydroplaning

We just completed hydroplane testing with a truck tire group at the Consumer Reports Auto Test Center. Technically speaking, we're assessing the ability of a tire to resist skimming on standing water. So far, the results are compelling, as we're finding that some tires do a much better than others in resisting hydroplaning.

Our test is actually a very simple one: We measure the speed when a tire starts to hydroplane on a puddle of water 3/8-inch deep. A good-performing tire will hydroplane at a higher speed than a poorer model. (Read: "Video: How to reduce the risk of hydroplaning.")

We test all truck tires for hydroplaning resistance, including the all-season, all-terrain, and winter truck tires. The tires are tested with a full tread. As a tire wears, it's more prone to hydroplane, which is why it's always wise to check your tires' tread depth and consider shopping for new ones when they approach 4/32 inches of depth. (Read: "Don't lose your grip in wet weather.")

The chart below shows the speed range of when tires start to hydroplane within each category. For example, some tires started to hydroplane as low as 46 mph; the best ones hold off until 57 mph. (Remember that next time you're driving on a highway in the rain!) A good-performing tire will have a favorable footprint and tread design to channel water effectively. Once a tire starts to hydroplane, you'll lose steering control--never a good thing. If this happens, you should lift off the throttle and slow down to regain grip with the road.

Other updates: As I'm writing this, extended tread-wear testing is being conducted in San Angelo, TX, on 36 all-season and all-terrain tire models. We'll run the tires to 16,000 miles to estimate their true wear potential; look for an update in a future blog.

We also just completed the second part of our winter testing--stopping on ice. In January we did snow traction testing with the good fortune of having plenty snow at our Connecticut test facility to evaluate the all-season, all-terrain, and winter tire models. (See our truck tire testing update on snow testing.)

Testing brake performance on ice is done on an indoor ice skating rink, limiting our test speed to just past 10 mph. Then we have to do a panic stop before hitting the boards at the end of the rink. You wouldn't think that 10 mph isn't very fast…until you find yourself sliding toward a wall. That's when the grip between a good and poor set of tires can make the difference between being in accident and avoiding one. The graph below shows the average stopping distances of the 12 winter, 13 all-terrain, and 23 all-season tires fitted to our test truck, a Chevrolet Tahoe. The bracket within each category bar shows the range of stopping distances among the best and worst models. On average, winter tires make good on their claim, stopping shorter than all-season and all-terrain models, which seem to have similar performance. But as the range shows, some winter tires stop no better than many better-gripping all-season and all terrain models. Incidentally, the longest stopping all-season tire was also the tire with least snow traction grip. Overall, the best-gripping winter tire stopped near an impressive 25 feet; the worst took over 47 feet. That 22-foot difference is well more than a car length. We can only imagine what that difference would be at a higher speed.

Bottom line: If icy conditions are common in your region, a good set of winter tires might make the difference in getting to your destination safely. Regardless, icy roads are a challenge for any car and tire, so it's important to slow down and to drive carefully.

See our tire buying advice and ratings.

—Gene Petersen