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Thread: Z6 cupping

  1. #16
    FLYINGREG
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    Quote Originally Posted by stan
    I have only 1700 miles on my R1200Rt. I have always kept a close eye on tire pressure.
    You don't mention what tire pressure you keep your tires at. Forget the factory recommended pressures and run 38-40 front & 40-42 rear and things will be better. Please note that the lower number for the front corresponds to the lower number for the rear, etc.. Also, you need to know that the higher pressures will not fix the cupped front tire. Live with the present cupping until you replace the tire in 6-7K miles, or replace the tire if you have a mind to.

    The fact these tires have absolutely no tread in the center of the tire does make me wonder about rainy conditions, but they have yet to be a problem in that department.
    The Z6 does quite well in the wet, so don't worry about the solid patch in the center.

    Hope this helps! Safe riding!

  2. #17
    Ozonkiller
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    I love the Z6's and consistently get around 12K miles out of a set on my '96 1100RS and they're exceptional in the wet

    BUT

    don't rely on the wear bars on the rear. On my first set I just started to touch the cord and still had, what appeared to be plenty of rubber before I got to the wear bars. That set had a lot of interstate miles on them so the rear was pretty flat. I contacted Metzeler and sent them pictures. I knew I had to be getting close, so it didn't come as a big surprise.

    My recomendation to Metzeler was to put a couple of dimples in the center like they do on slicks.

    I've just ordered my 3rd set in preparation for my ride to complete my quest to ride through all of the lower 48. 44 down 4 to go.

    Next year, Alaska

  3. #18
    FLYINGREG
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    Quote Originally Posted by Ozonkiller
    I love the Z6's and consistently get around 12K miles out of a set on my '96 1100RS and they're exceptional in the wet
    12K on a set of Z6's, WOW! The Z6 were my worst wearing tires to date on my RT, only getting 6K miles out of them. I do ride pretty agressively, but in comparison, the 880ME's from Metz gave me 10K out of the set and the ride handling was about equal to the Z6's. Really couldn't tell them apart. Sure didn't effect my riding style any.

  4. #19
    Rally Rat torags's Avatar
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    I got 3K miles on an overinflated Z6 on my K75, with spirited driving. I no longer overinflated.

    Under inflated tire edges wear quickly, over inflated tire centers wear quickly.

    On front cupping: Perhaps the fork tubes are out of synch. No where is it written they have to wear evenly, we just assume it.

  5. #20
    FLYINGREG
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    Under inflated tire edges wear quickly, over inflated tire centers wear quickly.
    That is why it is so important to keep tires properly inflated.

    On front cupping: Perhaps the fork tubes are out of synch. No where is it written they have to wear evenly, we just assume it.
    Fork tubes "out of synch" is a technical term I have never heard before. Can you explain what you mean by that term.

  6. #21
    Rally Rat torags's Avatar
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    Are they adjusted evenly, are all the seals in each OK or is one preloaded more than the other?

    If there is uneven response to loading it can create an undetected warble that may create lateral wear leading to cupping.

    If a bearing is worn & has excessive play - it can create cupping.

  7. #22
    Rally Rat Mar's Avatar
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    I have about 8K on my Z6s and I'm replacing them with ME880s tomorrow. I do not like the Z6s and I won't buy them again. The rear wore flat quicker than any tire I've had and if I'm not mistaken, the Z6s have a steeper profile, so when the tire wears flat, there's a pretty good change between the side and the worn portion. My bike (the R1150R) does not handle as well now as it did when the tires were not as worn (well... duh... but it seems worse than usual).

    I also don't like the fact that there are no sipes in the rear tire. I think the rear tire is near worn out, but I'm not sure. I surely don't want to see the cords showing through.

    So, off they go tomorrow. I wore off as much rubber as I could at Branson.
    Marilyn Roberts
    R nineT, R1200R, R100 Mystic

  8. #23
    Rally Rat Mar's Avatar
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    Quote Originally Posted by torags
    I got 3K miles on an overinflated Z6 on my K75, with spirited driving.
    You put Z6s on a K75? Doesn't the K75 use bias ply tires? The Z6 is a radial. Bridgestone BT45s are great on the K75.
    Marilyn Roberts
    R nineT, R1200R, R100 Mystic

  9. #24
    DZIMBRIC
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    Quote Originally Posted by torags
    Are they adjusted evenly, are all the seals in each OK or is one preloaded more than the other?

    If there is uneven response to loading it can create an undetected warble that may create lateral wear leading to cupping.

    If a bearing is worn & has excessive play - it can create cupping.
    I didn't know you even had a shock in the fork on a paralever. How do you adjust the individual pre-load for the fork?

    I bought three sets of Z6's when I had my '04 RT. I got 10K-13K out of each set. On my last set I replaced the rear due to a lot of interstate miles but the front still looked good enough to last for a whuile when I traded the bike.

    I always ran 40-42 on the tires but I really pushed their limits for wear.
    The rear is definitly hard to judge for wear. As far as wet weather riding they stick real good.

    Another cause may be more weight on one side of the bike than the other. Do you carry more weight in one sadllebag than the other?

  10. #25
    Riding Dutchman jacco's Avatar
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    Quote Originally Posted by dzimbric
    Another cause may be more weight on one side of the bike than the other. Do you carry more weight in one sadllebag than the other?
    If the issue is uneven wear on one side compared to the other, but similar around the circumference of the tire, then crowned roads might also be the culprit (in addition to the uneven loading that dzimbric is suggesting). We have those here a lot and my front tire tends to be most worn just off center to the left (when you sit on the bike). But this cupping we're talking about here is different levels of wear at different points along the rotation direction of the tire (circumference), correct? Like the kind you would expect from a bent rim?
    Jacco
    2000 R1100R
    2003 F650CS

  11. #26

    Cupping Theory...

    I read somewhere but can remember just where, that the problem with MC Tires is that they have a rounded profile. At the very center is the largest radius of the tire. As you move out to the sides of the tire the radius gets smaller and smaller. The tread contact patch is a long oval shape...the center tread crosses the longest part. The left/right sides of the contact patch are therefore smaller in area than the long center area.

    There is a constant tug of war between the center of the contact patch and the left/right sides of the patch. The center parts says "the tire will rotate at the speed I want!". The two left/right sides of the patch (which, don't forget, are smaller in radius) say "nothin doin bud, we want the tire to spin just a wee bit faster". The two sides being lesser in contact area don't win the argument and therefor actually slide, grip, slide, grip,...you get the idea. That is how the cupping pattern is formed.

    Maintaining correct tire pressure is the best way to minimize this constant "tug-o-war"...you'll never eliminate it though.
    '99 R1100S - Can't understand why so few are riding the "S" model BMWs...

  12. #27
    Rally Rat torags's Avatar
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    Quote Originally Posted by Mar
    You put Z6s on a K75? Doesn't the K75 use bias ply tires? The Z6 is a radial. Bridgestone BT45s are great on the K75.
    Put a z6 on the rear, front was bias ply. They didn't make a radial in front wheel size. I never had handling problems, I usually keep the front light in sweeps.

  13. #28
    Rally Rat torags's Avatar
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    Quote Originally Posted by Mar

    I also don't like the fact that there are no sipes in the rear tire. I think the rear tire is near worn out, but I'm not sure. I surely don't want to see the cords showing through.

    No sipes on rear? Mine has sipes running up the sides, but little or none on the center strip, that concerns me (re:aquaplaning)

  14. #29
    Danger: Keep Back 500 Ft FredRydr's Avatar
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    When the ME Z6 Roadtechs were first released, Metzeler had a lot of information on the UK website, with a detailed description of advances over their own ME Z4 tires, and a comparison chart of various attributes. The last time I looked, that information was moved or removed. My recollection is that the front tire passing through water makes way for the rear tire's bald midrift - when upright. The treadlife of the Z4 and Z6 remained the same, but adhesion properties were improved, especially in the wet, notwithstanding that bald stripe.

    The wear bars are aligned with the little elephants on the sidewalls. I still have a hell of a time finding them - the wear bars, not the elephants.

    I ride a 525lb. 2002 R1150R with Z6s front and rear at 36/40 psi, and my bulk puts another 200 lbs on the tires. I live in the central Pennsylvania mountains, so lucky for me my riding is often heeled over to one side or another. All this results in rear Z6s lasting 5,000 - 6,000 miles, and about half as much more on the front. It's been hard to tell lately, because I keep getting punctures in the rear!

    Fred

  15. #30
    Dang! RatSnake's Avatar
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    Quote Originally Posted by FredRydr
    When the ME Z6 Roadtechs were first released, Metzeler had a lot of information on the UK website, with a detailed description of advances over their own ME Z4 tires, and a comparison chart of various attributes. The last time I looked, that information was moved or removed. My recollection is that the front tire passing through water makes way for the rear tire's bald midrift - when upright. The treadlife of the Z4 and Z6 remained the same, but adhesion properties were improved, especially in the wet, notwithstanding that bald stripe.

    The wear bars are aligned with the little elephants on the sidewalls. I still have a hell of a time finding them - the wear bars, not the elephants.

    I ride a 525lb. 2002 R1150R with Z6s front and rear at 36/40 psi, and my bulk puts another 200 lbs on the tires. I live in the central Pennsylvania mountains, so lucky for me my riding is often heeled over to one side or another. All this results in rear Z6s lasting 5,000 - 6,000 miles, and about half as much more on the front. It's been hard to tell lately, because I keep getting punctures in the rear!

    Fred
    My K12GT and I just rode through a downpour of frog strangler proportions on the way home from Branson on Sunday. My Z6s stuck to the pavement like glue. No sign of aqua planning or slippage of any kind.

    I got 12K out of my last set, which was about 4K more than I got on the original Z4 tires. I think the 12K was due to my spending as much time as possible on the sides of the tires (twisties). Too much on the high speed slabs will wear out the centers prematurely.
    RatSnake
    Dennis Murphy
    Third Lake, IL
    2013 R1200GS BMWMOA, IBMWR, AMA Rounder #43

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