Metzeler Interact Tires - First Ride

Metzeler Interact Tires - First Ride

Metzeler Interact Tires - First Ride

In 2009, Metzeler introduced a higher level of versatility into a modern radial tire in a creative, technically sophisticated way when it gave life to the first member of the "Interact" family, the Roadtec Z6.

Rather than resorting to multi-compound technology for superior handling and extended mileage, Metzeler's designers exploited the hysteresis characteristics of rubber by optimizing the working temperature in the critical bands of the tire profile. In the case of a touring tire like the Roadtec Z6, they kept it cooler on the center to limit wear during long highway runs and hotter on the shoulders to increase grip to deliver greater and safe cornering ability.

To accurately differentiate working temperatures, they modulated tension of the steel cords in the zero-degree belts wrapped around the structure of the tire. Think of it like the tuning of the strings of a guitar: Higher tension is applied to the belts on the center zone to enhance rigidity and stability for lower working temperatures and less wear. The belts on the outer edges of the tread feature a lower tension to induce heat buildup, which improves grip generated by the relative contact area. The Interact approach proved a remarkable technical success and left a free hand for optimization of tread compound.

In 2010, Metzeler developed the Interact M5 Sportec to offer the benefits of its new technology to sportbike owners. The M5 features a more complex structure: The zones for the levels of tension grow from three to five due with the addition of two highly tensioned belts at the extreme outer edges of the tread. The purpose is to prevent any deformation when torque is applied while accelerating out of a corner with the bike leaned over. The tread compound is aimed at providing above-average mileage.

In 2011, the Interact family was completed with the addition of the ultra-high-performance K3 Racetec, which goes back to three tension zones. But here, the center one is the low tension one, while the outer ones, which are rather wide, use very high tension belts. The less-tensioned center zone maximizes grip for straight-line stability under acceleration and at high speeds, and, most importantly, for extreme braking. The outer, higher-tensioned zones ensure great profile stability under extreme loads from hard acceleration at maximum lean angles. Here, the compound is a bona-fide race spec--no corners cut.

Metzeler Interact Tires - M5 Sportec, Z8 Roadtec and K3 Racetec.

Metzeler Interact Tires (left to right) M5 Sportec, Z8 Roadtec and K3 Racetec.

Timed to coincide with the launch of the new K3 Racetec, Metzeler evolved the original Z6 Roadtec into the Z8 Roadtec, which is "new and improved" in both compound and profiles. The inner architecture remains unchanged and is based on three tension zones: central high tension for long mileage and milder tension on the edges for good grip when cornering. The compound here is primarily aimed at enhanced mileage.

The press launch for the new tires took place on the challenging Cartagena racetrack in Spain. Metzeler brought the latest three variations on its Interact theme. Originally, the new Z8 Roadtec was intended only for the road session of the test, but I was able to have a set available also at the track. To have the most accurate return from the test, in terms of analysis of the performance potential of the three tires, I selected to run the whole test on the same bike--a 2011 Suzuki GSX-R750--that was sequentially shod with the M5 Sportec, Z8 Roadtec and K3 Racetec. The M5 was used as the benchmark; being the most versatile, it must perform at a high level on both road and track.

M5 Sportec

Indeed, I confirmed the M5 Sportec is superbly capable at the track, getting the best out of the well-balanced chassis of the new GSX-R750. The M5 enhanced the response of the front end and stability at speed (120-mph readings recorded at the end of the main straight). The homogeneous front and rear profiles ensured a perfectly neutral response not only around second-gear corners and hairpins, but also when negotiating the two third- and fourth-gear long bends that kept the tires under a sustained, heavy load. Solid straight-line stability allowed for a liberal use of the great stopping power of the Suzuki's new Brembo Monobloc brakes. Knee-scratching lean angles were embarrassingly easy, and applying power out of second/third-gear corners did not induce any loss of rear-end composure.

Z8 Roadtec

The Z8 Roadtecs were installed immediately after the runs on the M5, and I must say that, once again, the touring interpretation of the Interact philosophy was surprising. Compared with the M5, the Z8 only took away a fraction of the previously mentioned ride quality. Great neutrality and consistency in keeping selected lines were the high marks. Lean angles were almost the same, and even around the long, high-load fast bends, the lower-tension bands at the outer edges did not show any tendency to induce weaving or loss of composure. The wider, high-tension center zone and harder compound only marginally increased braking distance from very high speed. In all, the Z8 proved incredibly capable. It's my guess that the performance gap in respect to the M5 might widen only in case of intensive track use on a heavier/more powerful 1000cc or larger sportbike.

K3 Racetec

The K3 Racetec was the final crescendo. This is a real sport/race tire that deserves to be used at the racetrack and not wasted on the road. It greatly expanded all the virtues of the GSX-R750 to very exciting levels. Steering is sharper, very solid and even more confidence-inspiring. Safety margins grew beyond any previous standard. I got into one of the fast, fourth-gear long bends a little hotter than sensible and, naturally, I was late at getting on the best line and started going wide. No problem, I just leaned the bike past its knee-scratching limit and it composed itself, getting back on the right line and then diving into the next corner.

But the real forte of the K3 Racetec is its ability to deliver enormous braking force. I could grab really massive handfuls of front brake and feel the bike decelerating at a rate beyond that of the reach of the other two types of Interact.

015 Metzeler Racetec K3

014 Metzeler Racetec K3

013 Metzeler Racetec K3

012 Metzeler Racetec K3

011 Metzeler Racetec K3

010 Metzeler Roadtec Z8 Interact

009 Metzeler Roadtec Z8 Interact

008 Metzeler Roadtec Z8 Interact

007 Metzeler Sportec M5 Interact

006 Metzeler Sportec M5 Interact

005 Metzeler Sportec M5 Interact

004 Metzeler Sportec M5 Interact

003 Metzeler Sportec M5 Interact

002 DePrato also sampled the more sport-touring-oriented Metzeler Z8 Roadtec Interact.

001 Cycle World?s European Editor, Bruno dePrato, laps Spain?s Cartagena circuit on the track-ready Metzeler K3 Racetec Interact.