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Thread: Tires pressures and wear patterns on 20" rims

  1. #1

    Tires pressures and wear patterns on 20" rims

    I wonder if anyone else has noticed this kind of wear on their tire. This is the fourth set of fronts that I've chewed through in under 3k miles, and as you can see the outsides are really taking a beating. Now of course I try to do most of my Z8'ing to curvy back roads at a spirited pace, but none the less this wear pattern is suggesting that the recommended pressure of 35psi on the 20" rims just isn't high enough for the fronts.

    My rear tire wear is completely even, so my -1.75 negative camber and 35psi is obviously the sweet spot for my driving habits on the roads I like.

    However, a life time of habit says never inflate the fronts more than the rears, but the evidence of the wear pattern suggests that maybe 2-4 psi increase in pressure would spread the contact patch out more evenly. What have you other 20 inchers found, and what do think about that?
     
    Andrew Macpherson

    Expert Z8 Inspections, with full support for both Z8 sale and purchases.

  2. #2
    Z8 Madness Z-acht's Avatar
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    I had the same problems with my Porsche: in Holland we have to many Roundabouts! Rounding a roundabout at higher speeds the car is hanging over to the right.
    Ton
    1 of the 71 original Dutch sold cars (jetblack/red)

  3. #3
    Z8Mania
    Guest
    Andrew, on some Ferraris the factory recommends more PSI in the fronts than the rears. I can't explain it, but over the years I have come to believe giving a few extra PSI to the fronts makes the cars feel a drop better to me- thats across the board. Give it a try, I think you might like it.

  4. #4
    I was under the impression that most car manufactures suggested a lower tire pressure for the fronts to promote understeer to save owners from themselves. Of course this doesn't apply to an experienced driver like Andrew or apparently all Ferrari drivers...
    My Best,

    Ed

    2002 Z8 Jet Black//Sport Red
    2012 SLS AMG Obsidian Black/Classic Red

  5. #5
    Z8Mania
    Guest
    LOL- if only all drivers of any marque could be half way decent. Thats true, but its not so simple because suspension geometry also plays a huge factor. Tire pressure is one place where we can easily tweak it a little bit..... In the case of Andrew's Z8 or my car also, we are not running the complete factory setup- we each have some tweaks in there- so some deviation from the recommended pressure is probably required. One thing we could do to really discover the correct pressure is measure the tread temperature in different locations just after driving with a pyrometer. That would tell you where its getting too hot and too cool.

  6. #6
    Z8 Ate My Homework! Norcal's Avatar
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    The z8 really needs more negative camber in the front. Perhaps an adjustable camber plate vs the Dinan caster plates?

  7. #7
    Administrator thegunguy's Avatar
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    I'll bring my pyrometer to the next drive. I have a spreadsheet somewhere of measurements when I was dialing in the old Exige.
    thegunguy

  8. #8
    Z8Mania
    Guest
    Very curious on what you find. I agree with Norcal but I think the Dinan is the best we can get!

  9. #9
    This weekend's 'Spring Fling' will be the first proper long drive with the new Pilot Super Sports, so based on the previous wear patterns discussed here I'm going to try running 39psi up front and 35psi in the rear to see how that feels.

    Based on previous wear rates on the 20" rims with my maxed out negative camber at the rear, and Dinan caster plates in the front, it really does seem like the Alpina suggested 32psi all round is a little too low for spirited back road carving, and as seen in this thread, even running 35 all round results in the fronts wearing in a way that suggests under-inflation.
    Andrew Macpherson

    Expert Z8 Inspections, with full support for both Z8 sale and purchases.

  10. #10
    Z8Mania
    Guest
    I think they are trying to slightly enhance the ride comfort.

  11. #11
    Z8 Ate My Homework! Norcal's Avatar
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    Ha! In general, I don't think they expected the z8 to be driven by full on hooligans! If they only knew.....
    I'm setting mine to 35/39 for this trip, and may bring my pyrometer too.

  12. #12
    Hey, who you calling a hooligan!

    I know, I resemble that remark
    Andrew Macpherson

    Expert Z8 Inspections, with full support for both Z8 sale and purchases.

  13. #13
    Z8 Ate My Homework! Norcal's Avatar
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    Of course, I was talking about you!

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