How to keep an eye on Metzler Z-6 tire wear.
The Metzler Z6 is a sport-touring tire, and has a dual compound (Note: I had some literature indicating Z-6's were a dual-compound tire, however Metzeler's site has changed and doesn't indicate that its dual compound any longer). The center is harder and has no sipes (treads) for improved mileage. The sides are softer and have sipes for improved cornering and wet traction.
Many people complain that they cannot tell when their rear Metzler Z6 tire is worn out due to the lack of tread sipes in the center of the tire.
If you are new to motorcycling: New tires are very slick until they are scrubbed-in. Ride cautiously for the first 100-200 miles (or use a wire brush to manually scrub the tires). I like to go for a "scrub-in" ride after getting new tires by taking the bike into the twisties. Be cautious, and slowly increase lean angles over the course of a 100-mile ride on your favorite twisty road.
However, I have never been surprised from worn tire. I've worn out six Z6's (and one Michelin Pilot Road) in the last 19 months by riding 40,000 miles in this period.
The trick is to pay close attention to the innermost tread wear indicator bar. Here is a close up of the wear bars on the Metzler Z6(B) tire. This tire is done, and no cords are showing yet.
The (B) designation indicates that this tire carries a heavier load rating than the standard non-B rated tire. The (B) tire is used on heavy sport touring bikes such as the BMW K-1200RS / GT and the Yamaha FJR1300.
Look at the sipe nearest the "TWI" stamp, and you will see three indicator bars. You can pretty much ignore the outmost two and focus your attention to the innermost indicator to get a feel for remaining mileage in the tire. When that innermost indicator is close (say 1/32"), you can consider the tire done.
Here, I've highlighted the wear bars or tire wear indicators with arrows. The red arrows are the most important ones to watch.
I've circled the indicators to highlight their locations. The most important one in this photo is the one on the far right.
Here's the TWI on the rear tire.
The front tire has a sipe down the center of the tire, and is easier to gauge wear.
A close up of the wear bars on the front Z6. This tire is also done.
Another view of the front tire, again showing the wear indicators.
Look for the "TWI" initials on the tire sidewall to locate the wear bars. TWI = Tread Wear Indicator
A kind guest posted this comment:
WARNING: the Metzler Technical Databook reports: "TWi = Tread Wear Indicator. Identifies those indicators located into the main grooves that appear when the tread depth is reduced to 0,9 mm approx".
In most european countries tread depth must be at least 1.6 mm.