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Tyre Wear/Suspension Setup - Pilot Power Pure

Discussion in 'Technical and Troubleshooting Torque' started by BennyV, Aug 3, 2011.

  1. I have an issue with tyre wear that I haven't been able to dial on out my 2011 Z1000.

    Currently running Michelin Pilot Power Pure's, although I had the same issue with the Previous Diablo Rosso's.

    As you can see from the image, the tyre is wearing unevenly and rolling the leading edge and lipping the trailing edges. This is more pronounced the closer to the edge of the tyre.

    Compression/Rebound seem to be pretty good at least from a handling perspective. Rider Sag is set at 30mm both ends although, I've had to wind the preload collar in almost all the way on the shock to achieve this so it's not perfect. Really need a heavier spring.

    Currently running 36/38psi cold although I have tried running 34/36 with similar results.

    My gut feeling was it's a rebound issue but I haven't been able to dial it out at least within the scope of the stock shock.

    Is there something I'm missing or is it just something to live with 'till I can justify putting a new spring and shock on the back?


    Edit: This tyre only has 1500km's on it and I dare say more than 1000 of that would have been highway due to a longer trip.
  2. I thought the wear was always related to the amount of lean you put your bike on ? hence my 'chicken' line is MASSIVE!!
  3. I'm not worried about the "Chicken Strip".

    You can see on the sipes the uneven wear front to back.
  4. I could never get rid of that on the power 2ct either , mine were worse than that. The dunlop D209rr didn't do it nearly as much nor does the GPRA11, I don't know why
  5. Surely that's pretty normal wear?

    The leading edge is 'folded' as it hits the road, leading to the lip, & the trailing edge rounds off?
  6. I see what mean!! Learning everyday and have never looked a tyre and noticed that.
  7. I am lead to believe that is from too low a pressure. Not positive. But what a Bridgestone rep told me once and it worked.
    We had a cruiser with a vibration that we could not pin point. And it turned up being the tyre. And the tyre being run at too low a pressure for the weight and it caused the leading edge of the following block to sit u because it was rolled.
    So yeah not real sure. If you get a vibe then lol maybe.
    PP's take a fair bit to get up to real sticky temp. And they are so light and thin they are a biatch to keep that temp up in n the road.
  8. I have heard that PP's need to run a bit higher pressure because they're such a soft carcass. To be honest I haven't tried running them any higher than 38psi cold. The front is wearing beautifully and I get great feel from it so I'm unlikely to change that. I'll try 40 in the rear over the weekend and see if it nets any results.

    MV could be right that it's just normal. I honestly don't know myself. The bike feels perfect on the road and in corners, so, it might be something I just have to live with with my riding style.
  9. I went up to 43 rear and down to 34, they still did the same thing but at over about 38 the back end would light up too easily for me. It has just occurred to me that I changed the geometry slightly when I went to dunnies by going from a 50 profile to a 55 that may have something to do with it?
  10. That looks like normal wear to me.

    When you lean over, the contact patch is made up of some rubber near the centre and some nearer the edge. The stuff nearer the edge has a smaller rolling diameter. As a result the tyre is trying to turn toward the inside. (Picture a cone rolling.) Because the bike is usually following a straighter line than the tyre wants to (because of the cone thing) the centre part is always pushing and the edge part is always being dragged along. As a result, unless you wheelspin out of corners like Stoner or Magee, you end up with a wear pattern at the edge that looks like you've been doing a lot of engine braking / rear braking while right on the edge of the tyre. If you do roll into corners on a completely closed throttle, and reach your maximum lean angle with the throttle shut, this wear pattern does get a little more pronounced, but even a 'corner under power' rider will still see it. My Pures look pretty much the same.

    I have some pics of the pure / power when freshly scrubbed in, and a few of the Bridgestones when fairly worn. I'm only going to post the links.
    This is the Pure front and Power rear...


    And these are the BT014.


    And so on....

    PS. That Power rear and Pure front are now well shagged, but then, they have over 9,000k on them, on a zx14. They have a right to be shagged.

    PPS. Benny, apart from your wear 'problem', what do you think of them? 2CTs are one of the replacements I'm looking at.
    • Like Like x 1
  11. Yeah my bro noticed his gixxer did that too after a bit of track work. i don't think its anything to worry about
  12. It's called block squirm and is caused by weight distorting the tread on the tyre carcass.

    The higher the load applied the more the tread distorts and the larger the lip on the sipe will be.

    Basically the tread is pushed into the sipe by the load applied, which means that it doesn't touch the road surface, once load is removed the tread springs back up unworn leaving it protruding above the reast of the worn tyre surface.

    Good underbelt construction helps reduce/stop the problem, depending on load of course.

    Block squirm is the reason that manufacturers try to make tread blocks so large for high performance vehicles, even ending sips short of shoulders which of course also increases contact patch size.
    • Like Like x 1
  13. I had the exact same issue but a bit worse. Apparently with a rounded leading and lipped trailing edge its supposed to be too much rebound and visa versa. BUT I have seen this on many other bikes as recently as last Sunday. I think now after reading Tacks post that he is on the money. I have run mine as high as 42/38 and they didn't feel good at those pressures. Settings have been all over the place chasing a good baseline to no avail. Last week fitted some M5 Metz and the bike is now unreal on my previous settings. I have heard similar comments from other riders about these tyres, too many people with the same experience.
  14. This happens to all my bikes, thought it was normal?
  15. watch this video everyone. it covers this subject in great detail.

    dave moss - tyre wear

    ps. if it feels ok then just ride it. its hardly got much wear on it for 1500km too, doesnt seem to have had much heat in it.

    i only use tyre wear as a rough indication, i just play with the suspension until it feels good and im going quicker.
  16. I've been very happy with the performance of the Pures. I don't have much to compare to though as my last set (OEM's) were a set of Diablo Rosso's that were less than great. They drop in weight was the most noticeable change from the Diablos and I haven't had any kind of "Oh shit" moments on them. Get much more feel and confidence out of the front. Haven't been able to spin up the rear out of a corner yet either so, props to the rear.

    I've been a massive fan of Dave Moss' channel on UStream and it's what led me to the conclusion that this wear is an issue; too slower rebound. I haven't been able to dial it out through the stock shock which to me could mean one of two things. The shock unit is crap. I know this for a fact that it isn't the greatest thing out there. Or, that it's normal.

    After reading responses from a couple of forums, I think I'll have to go with the overwhelming majority and say that it's normal wear for a road tyre.

    I've been pretty happy with my bike setup at the moment and the actual tyres themselves. They're plenty sticky enough for my needs and the wear looks pretty good at this stage for the km's (Unevenness aside).
  17. This is caused by back pressure from decelerating into corners. Normal engine braking as you lean in. Don't stress it.

    If this was on the front tyre you would need to look at tyre pressures and suspensions settings, of which you would generally find to be on the soft side.

    To correct the rear tyre you would have to change the way you enter corners. Slow down too much then turn in with a neutral throttle. Neither accelerating nor decelerating. It will take a lot of practice and generally will be a major waste of time and effort for the sake of saving a bit or leading edge tread. An alternative would be to accelerate harder on the exits whilst still on a reasonable lean in which case you will wear the trailing edge more and in effect round the tread pattern.

    Simple answer, ignore it. The tyres are of a soft compound and therefore wear easily. It's just the price you pay for increase sticky.
  18. I'm a huge fan of Dave Moss too and I try and watch all his stuff, but I don't always agree with him about everything. I exchanged some (5 ~ 6) PMs with him a couple of years ago, when he started loading Sportsbike Wrench up on YouTube, and I didn't convince him and he didn't convince me.

    Dave's got infinitely more experience than me in dealing with smaller and mid sized sports bikes, modern up to date stuff, on circuits and at track days. He deals with everyone from medium, even slow group track day people, right up to (lower end) professional racers.

    I started riding 4 cylinder bikes in 78, and 1100cc jap bikes fast on the road in '80. My formative experience is on real roads, at high speed, on crossply tyres, on air cooled 11s with frames made of raw spaghetti.

    Result is Dave and I have a different metal picture of what the major limits and problems are. I see control and chassis integrity and getting the bike settled and stable and neutral as the first and primary issue. You've got to have confidence in the bike - that's the first and most important thing. Dave sees getting the tyres in the right temperature zone and then preserving them as the first and primary issue. In our respective arenas, we both have a point, but it means we see the role of damping differently. Dave primarily sees damping as being a way to help the tyre stay in touch with the road, and helping the bike to stay stable and controlled is secondary and less important. I see it the other way around. I see having the bike settled and calm and controlled under me, over bumps and crests and dips and stuff, as far more important to going quick than outright grip.

    The place where this difference of opinion has a real world effect is in rebound damping. Dave likes to run as little as he can get away with, because it helps keep the tyre on the road, and it helps (slightly) the rear of the bike to ride higher in its stroke. It prevents the rear ratchetting down (or jacking down) over a series of bumps. I like to keep the rear rebound reasonably firm, because it has a real and noticeable effect on damping down unwanted chassis movement and sloppiness. If I was going to ride at the newly resurfaced track in Italy (Mugello?) I'd do it Dave's way. If I were going to ride at the Isle of Man - I'd do it mine.

    I'm drifting off topic. The wear pattern in the original post seems unavoidable to me, unless you make the contact patch very small. The thing Tack said about tread squirm is exactly right, and the thing I said about the shape (in 3 dimensions) of the contact patch and the conical shape wanting to turn, is the reason the rubber in the centre shows 'drive' wear and the rubber near the edge shows 'braking' wear. Nothing you do with springs or damping is going to change that, unless you futz things up so badly that other problems are introduced which mask it.

    I am speculating a bit here, don't really know, but perhaps a bike that spends half its time upright and half all the way over on the shoulder, like a 125cc GP bike, might show a different wear pattern, but a larger fast road bike, 4 stroke, engine braking while tipping in, more time spent in the 35 ~ 40 deg lean range than the 50 ~ 60 lean range, then I don't see how you can not get that wear pattern. Some models of tyre might have tread patterns that make it a bit less obvious and noticeable, while some smack you in the eye with it, but they'd all do it.

    @Gixr.thou - It isn't just the engine braking, because I get exactly the same pattern on my front tyres, and believe me, I don't brake like a demon while I have my knee on the deck. I brake hard while upright, trail them off as I tip in, and have no brakes on at all once I'm fully leaned, but that isn't what my tyres say. They say I don't brake at all when upright, that I brake some while I'm tipping in, but I hang on the front lever like a braking-fool while the bike is right over on its side. The reason is because of the geometry of the tyre - same as at the back.

    Another thing that it's good to pay attention to, is the surface texture of the tyre, because that can tell you the operating temp range, and how hard the tyre's been working.

    Tyres that run real cold and don't see any hard use simply have a smooth matt finish.
    Tyres that work hard at lower speeds and temps get a rough, sandpaper looking finish. They usually have a paler grey sort of colour.
    Tyres that work harder at higher speeds and temperatures get a darker black colour to them, and the surface looks smoother, like wax or a nylon chopping board - slightly polished. You can see sometimes where the edge isn't getting hot but the tread half way to the edge is.
    Tyres that get too hot get an oily look and feel about them. You can kind of see rainbows in the surface. They feel cold and hard to touch when they've cooled, and they kind of look like they've been cooked. They can fade to a paler black with a blue tinge, or a tan / orangy sort of tinge to it - or sometimes both on the same tyre.
    Reading the surface texture can be difficult and misleading, because different companies and different models use different compounds and they behave in different ways. I find there's a certain commonality in the way all Michelin tyres and all Dunlop tyres behave, and many Bridgestones as well. But making a direct comparison between a Dunlop and a Bridgestone can be very misleading. What looks like (let's just say for example) cold tearing on the Michelin, and graining on the Dunlop, can look like wiping or peeling on the Bridgestone, but it's showing exactly the same thing - it just looks different on the 3 different tyres.

    [edit] I'm going to stick up some more pics of this over on the tyre pressure thread, which has wandered into the same subject territory.

    • Like Like x 2
  19. Here's a BT016 showing the same wear pattern.
  20. a worn leading edge of a sipe and raised rear edge means that your rebound is set incorrectly.

    it usually means its set too fast. most streetbikes i ride have not even close to enough rebound damping control when you start to push hard. but if you set the rebound to work great at track speeds it can 'pack down' (rebounds too slow to recover in a series of bumps) and will ride very crap and not hook up.

    but sometimes this pattern can be reversed across the whole tyre, eg the very outside has the leading edge worn down then closer to the centre the leading edge is raised and the trailling edge down. this basically means that there is a fundamental valving issue with your rebound in your shock.

    if its like this i just try and get it to look nice on the edge of the tyre as i would rather have good edge grip but sacrifice grip when i'm laying on the power hard as sliding looks cool :D

    but for outright speed you would get your shock revalved.