Tire Question

Discussion in 'Technical Forum' started by Beatinpileguy, Jun 15, 2013.

  1. Beatinpileguy

    Beatinpileguy Member

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    Chris Meyer
    Attached is a couple photos of my rear. This is after 20 laps.

    Tire pressure was 28 off the warmers and the tires are Pirelli Superbike slicks.
    It is on a Ninja 650R.

    Any suggestions what I can change other then not ringing it's neck off the corners?
     

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  2. Spooner

    Spooner Active Member

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    Few things with that.

    First your tire pressure is too high coming off the warmers. Max you tire pressure should be is at 26psi hot. With that, I'd also like to know what your pressure was immediately coming off the track. (?) I'd assume that it was closer to 30?

    The first thing I'd do, unfortunately is to get your warmers up to temp for the 40 to 60 min and adjust your pressure down to 24psi hot and then go out to see how it holds up for 10 laps or so. Then once you're done your session, come in and immediately check your pressure again and adjust to the desired 26-25psi sweet spot. (Keep in mind that 25.5 to 26.5psi on SC2 tires, has been the magic spot for all the different tire sizes since I can remember at Stratotech.)

    There could also be an issue with your rear shock as well. That is set up to hard/to soft...

    Next time your at the track, please stop by the Pirelli Tents and we'll great you getting some proper tire wear.

    ~Scott
     
  3. Fireman

    Fireman Well-Known Member

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    I'm fairly sure we chatted in the pits. But here it is incase it wasn't you.

    The tire will accommodate you driving off the corner. There is no need to change your riding style. Even if your slow at apex at the beginning of the season and you are making up for that with a fist full of torque (most of us do early in the season especially).

    So a couple of things. First as Scott pointed out, your pressures are high. Now that usually makes for less grip and better looking wear due to higher surface temps. So I doubt this is your issue. The next thing to look at is your suspension setup.

    When did you last setup your sag? (important to tire wear)? When was that shock last serviced? I have seen this kind of wear from cold tearing before, however the SC2 rears are pretty good at avoiding that. So I would look at the suspension.

    As scott stated. Grab either scott or myself next race weekend. We can sort you out.

    Justin
     
  4. macbayne

    macbayne Active Member

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    fwiw OP, Justin is pretty good at suspension advice, lol!

    took 1.5 seconds of my lap times in one fell swoop last trackday. justin also likes to be paid in mars bars, too.
     
  5. Beatinpileguy

    Beatinpileguy Member

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    Ya Justin that was me you talked to. I looked back at my notes and it was 28psi off the track, 26 off the warmers...my bad. I set it at 26 as per your instructions after the first race. it showed minor tearing when you looked at it then but really got bad later in the day after the lightweight super bike race 10 laps later. With the warmer track temps I should have maybe knocked another pound or two out. Either way there was no traction issues.

    Sag was set that weekend and it is a brand new unit. As far at the throttle with it being a bit shy in the power department I am able to get quite hard on the gas very early. I was experiencing no spin or slipping.

    I will come by and see you or Scott. unfortunately it may have to wait till round 3 as I will be unable to make 2 due to conflicting events.

    Thanks for the help guys!!
     
  6. Dean

    Dean Active Member

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    Usually, with wear like that, it's a rear suspension issue. Usually too low of a spring rate for tearing like that, so the bike is squatting under power and tearing. I think it would actually be worse with lower pressures and that the higher pressures actually helped from killing the tire.
     
  7. nac.00

    nac.00 EMRA Executive Member Staff Member

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    Dean and Justin are right ... check spring preload/rate also make sure there's not too much compression in the rear
     
  8. Ducbert

    Ducbert Active Member

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    I am not a suspension expert nor a sales person, but here's what I experienced and what I went through:

    Tested and tracked pressures for 4 rounds - No success so......I got drastic:

    #1 - Suspension - Stock shock was to light and set wrong - Had it set by someone who knew what they were doing
    #2 - Was suggested I buy a new shock - Bought new Elka, had it setup still had problems with tearing
    #3 - Wrist/Throttle - Charging hard out of the corner, needed to carry more corner speed (easier said than done at the time)
    #4 - Changed tire compound (went to a hard compound then soft) - No success
    #5 - Change tire brands - all bike setup remained, problem was almost gone ( I believe some tires work better with some riding styles - tire is not better or worse, just better for you and how you ride at that time)
    #6 - Dave S. did some more fine tuning, took out some rebound dampening (so the rear would come up faster), next sessions, completely gone, even wear and 1s faster per lap. Finally....

    First things to try/change - Listed from cheap ones to costly:

    #1 - Longer in warmers, good heat saturation
    #2 - Pressure's - I use to keep a record of pressures(cold vs hot), tire wear and ambient temperature (find the right combo) + dates and wear vs feel (anal yes but I needed to solve this costly problem)
    #3 - Try adjusting the shock - speak to one of the clubs suspension "Guru's"
    #4 - Try a different tire brand or compound(if your tearing up tires, the cost is the same, regardless of brand or compound - buy take off's)
    #5 - Go back to #2 - still fails go to #6.
    #6 - Buy new shock, set it up go back to #2.

    By round 5 I had finally solved my issue, only cost me 4 sets of tires and 1 new shock....I am not claiming changing tire brands is the answer but this problem can be attributed to more than one variable and the fact that changing brands was the last thing I did, could just be coincidence. I hope my experience helps give you some insight and saves you some $$$.

    Links discussing cold tear/tire wear facts:

    http://www.motorcyclenews.com/MCN/P.../nov1510-why-are-tyres-yearing-after-10-maps/

    http://www.youtube.com/watch?v=izaxhNfMnog

    http://www.onthethrottle.com/howto/dave-moss-unsprung-tire-wear/
     
    Last edited: Jun 20, 2013
  9. JDS

    JDS Active Member

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    Good info. I think #3 has alot to do with it.
     
  10. Dean

    Dean Active Member

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    I'll just say this that sadly, to a new racer, suspension is usually the last thing looked at. They will try race gas, motor work, power commanders, jetting, etc. They'll do everything to make the motor faster and more efficient. Those are last steps, once you are outriding the bike and need more.

    Step 1.) set basic suspension
    Step 2.) set the rider's basics skills and comfort levels
    Step 3.) make sure the basics are ingrained in the rider
    Step 4.) tweak suspension
    Step 5.) upgrade suspension to match riding style
    Step 6.) upgrade motor/injection/fueling to match style

    It only took me 6 years to realize that and a whole lotta money. Of course there are rare exceptions, but most will follow this path. Hopefully a lot quicker than I did.
     
  11. Beatinpileguy

    Beatinpileguy Member

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    Just as an update, after an entire round with Justin's help we messed with the rear setup and had no real improvements. We ended up adding a bunch (10 clicks) of compression, slowed the rebound by 7 clicks and the tearing stopped getting worse. After great debate I took Justin's advise and spooned on a new DOT rear. The mix of the harder compound and our suspension adjustments have completely stopped the wear issue and in turn I was able to go from a 1.07.65 best to doing a 1.04.67 in round 5.

    Thanks for all your help Justin!
     

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