No matter what aspect of vehicle performance you're looking at – acceleration, braking, cornering or ride quality – it all comes down to four patches of rubber on the road. You can have the best engine, the best suspension or the biggest brakes, but if the rubber can't transmit the forces, it can all just go up in a puff of acrid smoke.
When Hankook appeared on the scene 20 years ago, the South Korean tire maker barely had a presence outside its home market. Hankook was not known for high-performance or even moderate-performance tires. Like the automakers from its homeland, Hankook has come a long way over the last two decades, having gained original-equipment supply contracts with all three Detroit automakers, active motorsports participation ,and is now trying to get a piece of the aftermarket performance tire segment. Hankook invited Autoblog out to a facility near its Akron, OH technical center to sample its Ventus V12 EVOs against Bridgestone's Potenza RE760 sports. Read on to see how they fared.
Photos Copyright ©2010 Sam Abuelsamid / Weblogs, Inc.
When it comes to buying aftermarket performance tires, most consumers don't get a chance to actually test different brands head-to-head the way they can when shopping for a car. As a result, they end up relying on the sales staff at their local tire store when it comes to replacing their rubber. Recognizing this fact, Hankook has being rolling a transporter around the country for the past couple of years with a pair of identical 2007 Mustang GTs to demonstrate its rolling stock to retailers.
Hankook's Ventus line consists of several grades of high-performance and ultra-high-performance rubber. Among the latter group, the V12 EVO sits in between the V4 ES and the high-end Ventus R-S3 and is available in a huge array of sizes from 17 to 21 inches in diameter and widths from 215 to 305 millimeters. The Mustangs we drove were running on 255/45-R18 rubber at all four corners, with the black car riding on Hankooks and the orange 'Stang on Bridgestones.
Our evaluation took place at the DriveTeam training center in Cuyahoga Falls, OH, south of Cleveland. DriveTeam has a large open vehicle dynamics pad where the Hankook engineers set up a course consisting of a double-lane change, acceleration into a long right-hand sweeper, a dive into a tight increasing radius hairpin, another sweeper to the left and finally a slalom section. We ran the whole course with the automatic transmissions in second gear and the traction control turned off.
All the tires were set to the same 32 psi when cold, but one of the first things we learned from the Hankook engineers is that their tires have much lower heat build up than the Bridgestones. Once they heat up, the pressure in the Hankooks jumps to about 37-38 psi while the Bridgestones climb to about 42 psi. Too much heat is the enemy of tires, especially higher-performance types. It can lead to a loss of grip, premature wear and at the most extreme end, failure.
Temperature build-up is largely caused by internal friction between the various components that make up the construction of the tire. The more the various layers rub against each other, the more the temperature climbs. According to senior project manager Dave Martin, the construction of the Ventus V12 gives it a big advantage in controlling internal friction as well as performance. The Ventus has an additional steel belt in the sidewall that wraps around the bead and stiffens the sidewall particularly during cornering. The Potenza doesn't have this additional reinforcement.
Similarly the Ventus has two nylon overlay belts in the tread section compared to only one on the Bridgestone. This extra reinforcement keeps the contact patch stiffer so that it retains better contact with the road even under severe loads. Heat that is generated from the flexing of the rubber has to be dissipated and thicker rubber sections reduce heat transfer. Hankook has taken advantage of the increased reinforcement to reduce the gauge of the rubber in the sidewalls for better heat transfer.
Another major difference between the two tires is the tread pattern, with the Hankook featuring a symmetrical tread with a large solid central block and the Bridgestone getting an asymmetrical pattern. The Bridgestone tread has a theoretical performance advantage when cornering as there should be more rubber on the road as the tire rolls. However, tire performance is far more complicated than what's visible on the surface. The interactions between the construction, rubber compound, forces and tarmac are too numerous to count. Just as automakers increasingly relying on computer modeling to design safety structures that can pass wildly divergent regulations, tire engineers are doing the same thing.
They can now simulate an almost infinite number of constructions and compounds under different loading conditions so they can reduce the number of hardware development iterations that have to be produced. When prototype tires are built, they are tested thoroughly against the models to validate the models and continually improve them. Most of the work that goes on at Hankook's Akron tech center revolves around modeling and the engineers there develop all of the tires that Hankook produces for the U.S. market. When the time comes for testing real rubber, the task is split between the Akron and Korea lab facilities, with on-vehicle testing occurring at the Cooper Tires track near San Antonio, Texas.
So how does all of this play out on the car? Unfortunately, we didn't have the opportunity for instrumented evaluation or even on-road driving. Our back-to-back, seat-of-the-pants exam tells us that Hankook has come a long way in the last 20 years. Over the course of several runs through the evaluation course we pushed each of the Mustangs closer to their limits. As the edge of adhesion approached, the differences became more apparent. The increased stiffness of the Korean tires gave them better grip under extreme turning loads. This was most apparent on the sweepers where the Bridgestones started to loose grip at the front axle before the rears, causing the 'Stang to understeer.
At the same 43-45 mph, the Hankook-equipped Ford had a much more neutral traction balance. As the Mustang reached the grip limit, the Hankooks exhibited a very progressive breakaway at both ends. We could just feel it beginning to slide sideways a bit, but the car never snapped on us. That's a very good characteristic for a street tire to have, especially for drivers that don't have a lot of training. You can approach and find the limits of adhesion without too much risk of immediately wrapping the car around a tree if you pass the peak of the mu-slip curve.
A sunny summer afternoon in Ohio didn't give us an opportunity to test the wet traction capabilities of the Ventus V12, but Martin claims it's substantially better than the Potenza thanks to its symmetrical tread pattern. The V-shaped blocks should do a much better job of evacuating water from the contact patch area than the Bridgestone design.
Overall, the Hankooks seemed to provide slightly better on-center feel than the Bridgstones through the slalom, but neither tire really had a huge advantage other than in the maximum front grip during steady state cornering. Our evaluation was obviously very limited in scope, but from what we did see and feel, Hankook is definitely a brand that tire shoppers need to take seriously. Hankook now supplies between nine and 11 percent of the original equipment tires on new Ford vehicles and eight percent of new General Motors products. Overall, Hankook is the seventh largest tire-maker in the world and expects to move up to sixth before long. Just as Hyundai and Kia have shown on the car side, the Koreans are a force to be reckoned with in tires as well.
Photos Copyright ©2010 Sam Abuelsamid / Weblogs, Inc.