Among the many low rolling resistance “eco-tires” being marketed this season is Bridgestone's Ecopia EP422, a Grand Touring, All-Season tire designed to have very low rolling resistance and therefore high fuel-efficiency. The Ecopia is also marketed as an ecologically conscious tire due to its construction. However, the real questions are: How does it handle and how fuel-efficient is it really?
Bridgestone kindly provided me with a set of Ecopias for a long-term test of those very questions. As part of my summer project testing various eco-tires directly against each other, I spent three weeks driving the Ecopias on my 2004 Prius Nerdmobile to get an idea of their rolling resistance and handling characteristics. I was quite impressed.
- Real fuel efficiency improvements.
- Quiet and very comfortable ride quality.
- Excellent wet and dry handling.
- Slightly mushy steering response.
Bridgestone's new rubber compound, much like those of the Yokohama Avid Ascend and Nokian EnTyre, takes advantage of new technologies to produce nano-scale chemical effects that allow for “controlling the interaction between polymer, filler materials and other rubber chemicals at the molecular level.” In essence, this nanotechnology creates tighter molecular bonds between the different materials - especially the natural and synthetic rubber blends - that make up the tire tread.
Fuel-Saver Sidewall Compound
The rubber compound in the sidewall and shoulders of the tire is specially designed to return energy back to the tire when flexing and control heat generation. Both of these features are added to lower the overall rolling resistance of the tire.
Using silica as a filler in the rubber compound is the magic ingredient that increases the flexibility of what would otherwise be a very hard compound, thereby improving both grip and treadwear.
Nylon-Wrapped Steel Belts
Ecopia's twin steel belts are reinforced with spiral-wound nylon to increase rigidity, ride comfort and high-speed control.
In keeping with Bridgestone's environmental focus, the Ecopias are constructed with 5% recycled rubber from post-consumer tires.
I can now say with great certainty that claims to great fuel-efficiency for the Ecopias are hardly vaporware. As soon as the tires were on the car I saw mileage readings spike by about 2 mpg, then creep up towards 3 mpg as the tires began to break in, an impressive proof of the fuel-efficiency gains I had been told to expect.
The first thing I noticed is that the Ecopias have a very soft ride. They don't quite get squishy, and the softness is not unpleasant, but the slightly balloon-like feeling took some getting used to at first. Within a few days the softness has become just a normal part of a smooth, nearly silent and very comfortable ride quality. Bumps, open joints, train tracks, all seemed to simply vanish into the tires' pillowy softness without leaving a trace. It was the first time I've ever really felt pampered by a set of tires.
Some heavy rainstorms moving through Boston for the past few weeks gave me the chance to go play in the wet as well. The Ecopias grip quite well in dry or wet conditions, never feeling dangerous or out of control. My only real issue was a certain lack of prompt steering response, as the soft sidewalls will somewhat dampen out control inputs.
The Bottom Line:
Bridgestone's Ecopia EP422 lives up to its marketing in a quietly impressive manner. The actual improvements in fuel-efficiency tracked very well with Bridgestone's claims, and the tires displayed excellent grip in all summer conditions. Three weeks of heavy use showed me tread wear that was minimal and even.
Ride quality is a somewhat more subjective issue. The softness of the ride took me some time to get used to, while my wife loved it from minute one. Drivers looking for fast and powerful “coiled spring” steering responsiveness will not find it here. Drivers looking for a soft and comfortable ride that swallows bumps and allows you to forget the tires are there at all should be very pleased.