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Avoiding sidewall cuts?

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  • Avoiding sidewall cuts?

    Hi Folks!
    New to rallyx as of a few weeks ago. After 2 events here in upstate NY, I've managed to cut 3 tire sidewalls. As the wheels n tires were new until the drive to the first event, this is guaranteed to be event damage.

    Car is a 17 Focus RS. 18x8 wheels with 225/40-18 Michelin Alpin S4 (i think). Any suggestions for avoiding problems in the future? pressures were 50 psi all around. (stock spec happens to be 46, but I don't think that is terribly relevant).

    Wouldn't mind full blown rally rubber even on an otherwise stock FoRS, but 18" is the min diameter to clear the stock brakes.

    TIA!
    Scott

  • #2
    Hmm. That's tough.

    Not sure any 18" tire exists that would prevent the type of damage you're describing. Depending on exactly when the cuts occurred in the turns it may be possible to alter how much understeer the car is experiencing (less understeer probably would lessen the likelihood of sidewall damage). Sorta like how some of the folks who regularly debead also regularly are at full-lock understeer through many of their turns. Not saying this is you, just some thoughts.

    Our evo came with brakes that were way too big for 15" wheels and we had to downgrade so we could run rally tires. I'm not gonna lie and tell you I couldn't tell the difference in braking as the change was noticeable. When rallycrossing it doesn't matter much though as we stop fine with the little brakes.

    When driving heavy, AWD, turbod monsters like your RS (and our evo) sidewall damage seems somewhat unavoidable (for example the last event had all four our rally tire sidewalls dramatically scuffed, no cuts fortunately).

    Sorry if that's not very helpful. I can imagine it's a frustrating situation (costly too).
    Max Lawson
    2006 Mitsubishi Evo IX MR
    National Champion 2015 PA
    2nd Place 2016 MA

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    • #3
      Along the lines of Max's ideas, can you perhaps dial in a bit more camber all around to try to lower the amount of sidewall rollover? Perhaps a bit more air pressure can lower the rollover as well?

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      • #4
        Thanks for the replies and your thoughts on this. Hard to say exactly where the 1st, worst cut happened (~1" long, no cord damage, 1/4" deep and at the bead) as I *think* it was at the first event and didn't notice it until after I was onsite this past weekend having swapped to street tires for a track weekend in between rallx events.
        The newest two were generated RF & RR essentially in the middle of the sidewall ...I don't recall experiencing much understeer at either event, although most passes through the ~180 turn this past weekend were akin to a 4 wheel slide through damp slop. Maybe that counts as an understeer condition in this context. Probably only a couple brief encounters of a tank-slap like, full lock turn each event (~15 total minutes of runs each event).

        I *wish* I could get more than -0.7 degrees of neg camber. Only alignment adjustment on a stock set-up is toe. Front toe out was even side to side for better autocross turn-in, but nothing crazy. Rear too has toe out, but just a touch. Have not checked alignment since the shop did it at the end of July. Based on handling at Watkins Glen 2 weeks before, the alignment going into this most recent rallx had to be at least pretty close to that July set-up I described.

        So... the issue sounds at least partially related to sidewall flex, right? As they all looked like they were result of the rotational tire force into sharp objects (sharp enough anyway) given the diagonal direction of the incisions, it seemed like it might NOT be related to flex. Almost like too much torque. ;-)
        Attached Files

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        • #5
          On the rally rubber topic. Check black rocket they have a 18"rally tire option

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          • #6
            Indeed they do! While the needed size exists, they are currently out of stock at Rocky Mountain. Nice to have the option. Thanks for the suggestion.

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            • #7
              They don't stock that size. They order them per request. At least that's what they told me when I called about then a few weeks ago.

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              • #8
                Just run tubes.
                Jim Perrin
                WNY Region
                NEDIV RX Steward

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                • #9
                  Funny. I don't know if that's a serious alternative or not, but sounds good to me.

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