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Track day tyre wear diagnosis please

Discussion in 'Technical and Troubleshooting Torque' at netrider.net.au started by robsalvv, Oct 25, 2006.

  1. Tyres [Mich pilot powers] are 2500kms old, with 1 cornering school and 3 track days... the rest road.

    There is unusual uneven tyre wear, a shiny outer edge on the lefthand side of the tyre after yesterday's track day.



    PI is 9 lefts and 3 rights... obviously something to do with my technique is doing this to my tyre... I didn't see the markings as significantly on other folks tyres...

    Is it an early tip in/long time on the side thing... a near worn tyre thing... and to cut the funny buggers off at the pass - a crap rider thing??

    Thoughts please!

    Tyrewear004.

    Tyrewear003.

    Tyrewear002.
     
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  2. I get exactly the same wear pattern around PI.

    It's from rolling the throttle on aggressively just after you pick the bike up and exit the corner. It flattens out the tyre just back from the edge 'cos you're apply the meat of the power on that thin strip which is also providing a lot of turning traction as well.

    I take it to mean that I could still be rolling the throttle on earlier, but me being the big pansy than I am, typically I won't roll on until I'm up at ~80% lean, rather than starting at 90-95% lean like I imagine that the quicker guys would be doing.

    I guess that ideally you wouldn't see any distinct plateau back from the edge, but rather the edge of the plataeu would instead be at the edge of the tyre, which would indicate that you're rolling the power on the moment that the contact patch becomes "full" again right at the edge.

    Seems to me that the pattern is indicative of someone (like me) who is only moderately quick out of corners. Not scared to power on strongly out of a corner, but hasn't yet learned to do it while feathering at the edge of traction.
     
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  3. Oh, BTW, PI is actually 7 lefts and 5 rights. Turn 5 is a right-hander, although it isn't much of an actual turn since you can just accelerate WOT right through it almost upright.
     
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  4. Roll through the corner with a little more speed and you'll see a more consistent wear across the tyre. It will rip up the edge a little more, with the extra cornering forces on the tyre from that increased speed, you won't be able to give it quite so much throttle as you are exitting (unless you're Capirossi) so the mid part of the tyre won't tear up as much.
     
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  5. Sorry, I knew so many other things would come into play.....

    Before rolling through the corner with more speed, you have to make sure that your riding skill is up to it on the day, that the suspension is set right, you have the right tyres for the situation, the right pressures,

    I wouldn't want someone attempting a faster corner speed and dumping it in the process :oops:
     
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  6. Also you might try different tyre pressures. The Michelin Australia guys
    tell me that Powers require more pressure than other tyres due to
    being lighter and having less structure. This would cause your tyre to
    flex less and build up less heat, thus melting less. Looks like your
    tyre is getting a little too hot. What pressure you using?
     
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  7. Thanks for the replies fellers. Much appreciated.


    On the issue of throttle control, I don't think I'm being aggressive. Infact, I'm trying like mad not to be... [highside coming out of siberia...ouch]

    As I come up to a corner, I set a speed then try to maintain this speed by rolling on a bit as I'm tipping in and then settle the bike to a maximum lean. Then as soon as my balls will let me, I start to gently roll on throttle to get the bike to track and then on the way out, gradually roll on more as the lean angle decreases, to the point where I'll be giving it a fist full when the bike is virtually upright.

    Well, that's what I think I'm doing!


    It occured to me that the wear pattern might be indicative of me tipping in early and staying on the edge for longer... maybe? yes? no?
     
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  8. Regarding tyre pressure, I was running 31psi on Monday, which was a 20-23degC day. Tyre wear was more even and bike felt stable. On tuesday, the ambient temperature increased to 29degC and I hadn't checked the tyre pressures... guess what? They were 35psi. I think this explained the "interesting" ride when they warmed up... the rear kept unhooking or squidging around - gave me a puckering moment coming out of siberia. The rear stepping out/unhooking went away when I reduced pressure back to 31psi.

    I showed a tyre tech the wear pattern and asked if he thought the tyre had been cooked and had gone off (i.e., one too many heating cycles). He didn't seem to think so.

    ...what to do, :-k
     
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  9. ahh stupid netrider i just made a massive post and i got some posting error :twisted:

    either your spinning the rear out of turns? doubt it from what youve said about the pace you were riding....but my old pilot powers looked the same when i learnt to spin the rear ont he exit.

    my diagnosis = tyre pressures too high
    = smaller contact patch
    = more heat & stress generated by accelleration
    = overheating of the tyre,
    which is why it looks smooth instead of balled up. because you spend so much time on that part of the tyre it becomes a problem, at some other tracks it may have been fine.

    31psi is IMO 1 or 2psi too high for a track like phillip island where you spend alot of time leant over. i wouldnt be surprised if you had hotpressures of 37-38psi
    the change in ambient temp makes a big difference too, as you noted.

    I would have started with a 29psi front and rear, maybe a 28 on the rear as theres quiteabit of accelleration in a lap, and gone from there. Ive found with pilot powers a 34-35psi hot pressure works quite well without sacrificing sidewall stability.

    PS road tyres will take a million heat cycles and still be fine. theyre designed to do it. I did 6 or 7 trackdays on my old pilot powers plus a race weekend and i set a new PB the very last time I used them. still had fair tread too sold them for $150

    next time you go out check your pressures as soon as you come in from a session, aim for the 34-35 mark when hot and i believe it will make a difference

    p.s - i could be wrong! :LOL:
     
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  10. Tyre pressure... what an interesting topic.

    Got this from the www.sasbk.co.za website:

     
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    • Informative Informative x 1
  11. In comparison

    The same track, day and type of tyre. Totally different wear pattern...

    [img:800:533:d85fdb6d1a]http://cejay.zenfolio.com/img/p765903497.jpg[/img:d85fdb6d1a]

    [img:800:533:d85fdb6d1a]http://cejay.zenfolio.com/img/p1069072342.jpg[/img:d85fdb6d1a]

    [img:800:1199:d85fdb6d1a]http://cejay.zenfolio.com/img/p773639992.jpg[/img:d85fdb6d1a]

    The photo's the rob took don't adequately convey how weird the wear pattern looked. The outside edge just looked 'squidgy'.

    I also got some nice slides as well, but I think I was being hamfisted.
     
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  12. were you two riding at similar pace?

    do you know your pressures cejay?
     
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  13. Cejay was doing 1.57's, I was doing at best low 2mins...

    My tyre had a similar pattern as Cejay's 2 track days ago... my riding style hasn't changed, but the tyre has less rubber now than then - less rubber to dissipate heat???... :-k
     
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  14. Should maybe start a new thread, but with summer coming on, I've started to notice a decent difference in 'cold' tyre pressure with ambient temperature changes. 32 PSI one morning, 35 PSI the next :shock: Will the 'warm' pressure difference be as substantial, and if so, how should I account for it? :?
     
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  15. Hey I just bought today a thingo that tells me my tyre pressures while on the go.... cost me $250. I tested it today and it is very accurate, can't wait to test it on the track to see how exact tyre pressures affect traction. It also tells me the the temperature of the air in tyres, that should be interesting too.
     
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  16. Sounds like a great device Johnny. Let me know if you see an effect from ambient temperature on warm tyre pressures!
     
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  17. Whats this called and where did you get it?

    OP: What pressures are you running (Hot), or cold if thats all you have.

    There is a very slight pressure tear. Its really hard to pick up on pilots but the good thing is its not like the PR (or other DOT) which will tear if your pressures 2 psi out. You can just make it out, its between where your on maintanace and as your picking the bike up and rolling on (orange peel area)

    You can see there is a minor tear that runs around the circumference of the tyre, maybe 1'' from the edge.

    Its shiny on the edge because your not peeling the rubber away when your leaning it. Its hard to say when your apexing, the front may tell more of a story but if you have done LVL 1 at PI you should know your tip in points. It might also indicate that your on maintanace for too long.

    I usually aim for 35-37 psi HOT on PP's on the track. This depends on what mood im in, how fast I feel like going, bike etc etc. Any less and I get sidewall flex from the PP which disrupts feedback, makes the tyres feel greasy when they are not, etc etc. You generally want a 5-7 psi increase in pressures after a session.

    On the road, I would be running 36 cold as a starting point. There is no real need to run any less unless you have a solid 20mins of twisties and your dragging knees, balling up front and rear tyres. Even then, I left mine at 36 front and 35 rear. Any less, they started to squirm, too much and they squirm as well. A lot of people have the mentality of running track day pressures on the road and these guys are not fast.

    Other tyres will have different hot pressures, it depends on the carcass and compounds.

    You wont heat cycle a pilot power, they are a synthetic tyre compound. As you get towards the end of their tread, they loose some grip. Just like any other tyre. Heat cycled is usually blue shiny surface, it could be hard, it could take ages to warm up or if they are really fcuked, wont warm up at all.

    I have a theory on why this happens to pilots but im not a tyre expert. Simply I reckon they dont have as much meat to deal with the flex to get the grip, so they spin up or slide. I originally had a theory it was heat sink related but the're greasy from cold all the way to the end of the session.
     
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  18. +1

    ?? Sounds very good, and valuable, for the track.
     
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  20. It's called 'Tyredog'
     
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