Tire life/tread depth

[challey]

Update on the original tire wear post:
I actually ordered a new Z6,, intending to mount it before heading to the MOA last week. As it turned out, the order was messed up and I did not get to change the tire, so I took my chances on getting to West Bend from Phila (about 1,000 mi). I thought that I'd get a new tire at the Rally if necessary and checked the tire frequently en route.

When I got to West Bend, it turned out that the guy in the tent next to me, also on an R, had just put new Z6s for his trip from the Chicago suburbs to West Bend. I was able to check the tread depth on his almost brand new tires - it was 6mm. My worn tires, now with nearly 8,000 miles, still measured about 4mm (maybe a tad under, call it 3.8mm). Those figures say that I'm using about 1mm of tread every 4,000 miles. Metzler's web site says that replacement should be at 1.2mm which left me with 2.8mm to go. If the relationship was linear, that would ostensibly be enough tread for another 11,200 miles (2.8 x 4000). While I wouldn't expect to get that kind of additional mileage, it did give me reasonable confidence that I didn't have to worry about my ride back to Phila.

I put about 2,200 additional miles on to/from and at the Rally, making the total miles on these Z6s now about 8,800. My measurement in the driveway when I got home was about 3.5mm. Since my depth gauge is not exactly a precison device, there is a fair amount of error in the measurements but the wear still appears to be roughly 4,000 mi per mm. It seems unlikely that this is the true wear rate - it would mean getting something like 19,200 miles - but the tire still looks good and the wear bars are not yet visble. I've got to believe that there are at least a couple thousand miles of life still left.

Charlie

[Biff's R]

Glad to see you made it there and back.

[Beemeridian]

safely

[DSKYZD]

Challey,

One thing to keep in mind when you are measuring tread depth on the Z6 is that there is no tread in the center of the tire. More tread is worn off the center than on the sides. I've had a Z6 with cords showing in the center and tread left from just off center on out to the edge. Just something to note.

DSKYZD

[challey]

Update to the update:
As I mentioned in the last post, I had what appeared to be a significant amount of tread left after the trip to the national rally. I have not really done much riding since getting back from West Bend, so I thought I'd do one last trip on the Z6s, a relatively short one from Philly to Southern VT. That trip was this past weekend and was just under 1,000 miles. Including some local trips, I now have just over 10,000 miles on the tires.

The rear tire shows just over 3mm of tread, measured at several spots on the tire in the sipes closest to the centerline of the tire. I know that this doesn't necessarily mean there's 3mm of tread left in the center of the tire but it's the best I can do.

I will be replacing the tire in the very near future and will save the carcass for a tire autopsy. It'll be interesting to see how much the tread depth in the centerline differs from that as measured in the sipes.

Charlie

[Sunbeemer]

I recently e-mailed Pirelli USA this question about my rear Diablo Strada with 7500 miles on it:
"I would like to know how can you tell when the rear tire is worn out (before cords show)? Without tread in the middle with wear bar indicators, how do you know if the tire has exceeded it's useful (safe) life?

They responded with this answer today:

Hello

The Diablo Strada tires do have tread wear indictors as all street tires are
required by law. To find the tread wear indicator look on the sidewall for the
letters TWI. Straight across from these marks are the wear indicators (baby
speed bumps) in the grooves. The closest TWI to the center of the tire is less
than 3/8 of an inch away.

As a rider you should look at the tires on a regular basis for air pressures and
damage as well as tread depth with the understanding that once the tread depth
falls to about 2mm the tire is more prone to hydro planning. At this 2mm level
the twi marks are easily found in the tread grooves and this means that
monitoring the condition of the tire once the tire falls below 2mm is critical
to your safety.

[challey]

To find the tread wear indicator look on the sidewall for the
letters TWI. Straight across from these marks are the wear indicators (baby speed bumps) in the grooves. The closest TWI to the center of the tire is less than 3/8 of an inch away.

This is essentially identical to what Metzler has done on the Z6. What all of us worry about is that since the TWIs are offset from the centerline, they do not accurately represent the wear in smooth center tread area. Pirelli seems to be saying that they have taken this into account. There have been so many reports of Z6s not showing wear bars and then suddenly revealing steel belts that this assumption is suspect, at least for Metzlers.

The other thing is that the "baby speed bumps" are difficult to see. Maybe as Pirelli says, when tread depth gets to 2mm they "are easily found in the tread grooves" but I can tell you they are almost impossible to locate otherwise.

When I change tires, I plan to dissect the old tire to measure the tread depth to see how it correlates to the TWIs. I also am wondering if it possible to safely pierce the tread of a new rear tire, perhaps with a heated piece of wire, to see what the depth is from the factory in the center. This test hole could also be used to monitor tread depth in the center over the life of the tire.

Charlie

[Sunbeemer]

I found the TWI marks on my rear Diablo and sure enough, there were "baby speed bumps" in the groove nearest the centerline of the tire, and after ~7500 miles, they are almost flush with the tread in that area since the groove has worn down to only ~2mm deep. Also, the center of the tire is beginning to look ever-so-slightly concave, so I guess that means it's time for new shoes!

Thanks to all who posted in this thread for the education!

[telliott]

I wouldn't trust those Z6s if I were you. Its hard to determine tread depth remaining when there is no tread in the middle to start with.

At the Bash, Mr. Beemeridian had a flattened Z6 with the same burning question. It had cords showing before he got home.

I also had this happen to me on my trip out west a coupla...err..yeah, a coupla years ago. Take a real close look at the tire. If it appears to be ever so slightly 'concave' for about a 1 1/2 inch swath across the middle, then it's about to go rubberless on you.

What Boxer said - The Z6 (and Diablo Strada) doesn't have tread across the middle, which is the area that wears the most, so it's very hard to tell when you're running out of rubber.

just be cautious.

I just had the same problem with the Z6, went to steel very fast on a trip. I have also had issues with the rear tire slidding way too easily with light use of the rear brake. See the recent thread on "rear brake". I won't be buying any more Z6's.

[geothepencil]

10K on a nicely treated set of Z6s isn't too hard to do. I get 11 or 12K on bikes weighing 100 pounds more than an R/R. Our rules are simple: No long trips on tires with over 8K and pay attention. You can see the wear marks and know when they are finally worn out. Due to an odd wear pattern with the bikes we have that they are on, the fronts get changed at the same time as the rear. We like the Z6. We also have other types of tires that have potential lives ranging from hours to immortal. They are all different !

geo

[telliott]

It's not just the wear pattern I don't trust. I'm uncomfortable with the tire sliding too easily and feeling "grabby" when encountering rough patches of pavement that run parallel to the road.

However, I want to add that this is my 1st R (lots of other BMW's, etc. for 30+years). I really won't know if this is a characteristic of the bike or the tires until I try a different tire. Maybe, I'll change my mind.

[challey]

Latest update:
Here's a picture of my rear tire, now with about 10,600 miles. The tread depth in the sipes closest to the centerline now measures just a hair over 3mm. It is difficult to see the tread wear indicator - it is close to the centerline in the sipe nearest to the TWI" marking on the sidewall. In fact, I really can't see it - the only reason that I know it's there is from the tread depth measurement at that point (depth there is just over 1mm).

It's obvious that this tire is near the end of it's useful life but it does appear to have a few more miles left. Perhaps the relatively long life is due to being run mostly lightly loaded (I almost never have a passenger). I'm also not a very aggressinve rider, as the still pristine elephant heads indicate - this also probably contributes to longer tire life.

Charlie