At the Consumer Reports Auto Test Center, the team continues to work on evaluating some 80 different tire models scheduled for a tire story and Ratings release. Since we last updated our blog readers, the test group has grown slightly from the 77, when we were still in the process of buying tires. Presently we've completed our snow traction and braking tests on ice, dry and wet braking and cornering, hydroplaning resistance, and rolling resistance. Still in progress is our vehicle tread-wear evaluation and our emergency handling assessment. Here's what we've found so far:
There are no magic tread compounds: Winter tires, as the name implies, continue to impress us for their short stops on ice and tenacious grip in snow. However, many of the best tires were also the worst when it came to stopping on dry and wet surfaces. How much worse? These tires needed about two or three car lengths longer than many all-season tires. We also saw similar compromises with all-season tires, as well. Likewise, the most impressive stopping all-season tires on dry and wet surfaces had dismal winter grip.
Some manufacturers try to bridge this seasonal gap by compromise: some tires deliver good all-weather grip but rarely reach perfection in any one weather condition.
Fuel economy savings: When we test tires, we measure rolling resistance, considered to be a factor in fuel economy. Tires that need more force to roll generally consume more fuel on the road. We continue to find tires marketed as fuel savers having low rolling resistance. While that's a good thing, how much money (or fuel) do you save?
To answer that question, we compared the fuel economy of the lowest and highest rolling resistance T-speed rated all-season tires. We placed a fuel meter in a Chevrolet Cruze and measured the fuel consumed over our highway fuel economy test route. Results were revealing: a 1.9 mpg savings using the low rolling resistance tires in our steady-state highway circuit. That amounts to a savings of $80 a year, based on driving 12,000 miles and gasoline costing $4.00 per gallon.
This was an extreme comparison, and depending on what, where, and how you drive, actual fuel savings could vary. Also, tires lose air over time and you need to keep them properly inflated for optimum fuel efficiency. According to the government, properly inflated tires can improve your fuel efficiency by 3.3 percent and save you 12 cents per gallon at the pump. Driving on low rolling resistance tires or not, if you don't maintain your tire pressure, you will squander any savings.
It is important to remember, rolling resistance is just one factor in a tire's performance. As testing continues, we'll determine which tires from this large group deliver the best overall performance and provide the Ratings to help drivers choose the models best suited for their needs.
That said, it is time to get back to testing.