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Last Post 16 Dec 2013 12:53 PM by  sirele
Is there such a thing as too much tire?
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Joe Weinstein
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08 Dec 2013 09:38 PM

    Hi all. The car will have front corner weights around 395 lbs, and rear around 490 lbs, running Hoosier A6s, and lots of power (480 or so). What size tires would you choose for this, if you could run any A6?

    Thanks!

    edfishjr
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    09 Dec 2013 04:41 PM
    All else being equal, no, there is no such thing as too much tire, assuming proper rims, suspension design, shocks, etc. and given that the widest A6 made is 345 in 18" and 335 in 17".
    Joe Weinstein
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    09 Dec 2013 05:48 PM
    So you would run 345s all around?
    Robert Puertas
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    09 Dec 2013 07:05 PM
    On an 1800 lbs car? Seems like 345's would be overkill.
    The 2000 lbs. CSP Miatas go pretty fast on 275's - of course they have about 1/4 the power...
    sjfehr
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    09 Dec 2013 07:59 PM
    Posted By edfishjr on 09 Dec 2013 04:41 PM
    All else being equal, no, there is no such thing as too much tire, assuming proper rims, suspension design, shocks, etc. and given that the widest A6 made is 345 in 18" and 335 in 17".
    Well, eventually, you'd get to a point where the weight (and rotating mass) of the wheel/tire and additional width of the wheel/tire hurts more than the grip helps.  Don't think you'd get there with DOT tires, though.

    hklvette
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    09 Dec 2013 08:16 PM
    You also can have too much tire if they dissipate heat faster than you can generate it via friction. I'm not sure if the effect can be so extreme that they won't get into their operating range or not.
    edfishjr
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    09 Dec 2013 09:12 PM
    Posted By hklvette on 09 Dec 2013 08:16 PM
    You also can have too much tire if they dissipate heat faster than you can generate it via friction. I'm not sure if the effect can be so extreme that they won't get into their operating range or not.

    This is the only possible reason I can think of for not going as wide as possible, assuming your suspension is capable of keeping the tire flat to the surface and all the other reasons why a tire might not be happy. I mean, we know nothing about this guys car. He might have reverse wings that lift the sucker off the ground at 60 mph! What size do the A-mods run?


    edfishjr
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    09 Dec 2013 09:16 PM
    Posted By Joe Weinstein on 09 Dec 2013 05:48 PM
    So you would run 345s all around?

    I've answered your question. I know nothing about your car. Do you have enough rim width? Can you keep the tire happy when cornering? If not, then wider will hurt, instead of help.


    Joe Weinstein
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    09 Dec 2013 09:19 PM
    Thanks for all your thoughts! There will be no appreciable aero at autox speeds.
    The suspension will be very capable, and plenty of room for wheels and tires,
    but if too big a tire means it won't ever get warm enough that a smaller tire
    would actually stick better, that would be a worry. I'd hate to invest too big...
    ron
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    10 Dec 2013 07:27 AM
    15x10 with 275 15s
    edfishjr
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    10 Dec 2013 05:34 PM

    Posted By Joe Weinstein on 09 Dec 2013 09:19 PM 
    ... There will be no appreciable aero at autox speeds. ...

    Not even remotely true. Unless you mean you don't intend to have any aero add-ons. I don't think there is a class that will allow you to run any tire you want that doesn't have an aero component to the rules???

    Joe Weinstein
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    10 Dec 2013 05:47 PM
    My car will have no aero provisions that will deliver appreciable downforce or lift at autox speeds....

    And I can run any wheel that would be appropriate for any A6 tire.

    Robert Puertas
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    10 Dec 2013 05:57 PM
    818?
    Joe Weinstein
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    10 Dec 2013 06:12 PM
    Nope, cooler than that. And a little lighter... The corner weights I give are with driver.
    It's a D2.
    Robert Puertas
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    10 Dec 2013 06:52 PM
    Well if nothing else, you'll be able to scare the cones to death. ;-)
    Markwrx
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    12 Dec 2013 11:25 AM
    Posted By Joe Weinstein on 10 Dec 2013 06:12 PM
    Nope, cooler than that. And a little lighter... The corner weights I give are with driver.
    It's a D2.

    Joe,  Are you getting a new car or just dreaming?  Tell us more.

    Mark


    Joe Weinstein
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    12 Dec 2013 11:27 AM
    Hi Mark, I'm getting a D2. Seeya next year!
    Alex Tziortzis
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    16 Dec 2013 11:38 AM

    A bigger tire/wheel will mean more rotating mass.

    Also, if you look at the lateral grip as a function of force per square inch, you will see it is non-linear. This means on a car that is very light, you may disproportionally be losing more grip than using a narrower tire/wheel.

     At the end of the day, one important thing is to use a wheel width that is matched to the tire width.

    One nice thing about CCW wheels is that you can get some extra outer shells and change the wheel width and not have to blow a ton on extra wheels (does take a little time to disassemble and re-seal, but no biggie).

    edfishjr
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    16 Dec 2013 12:06 PM
    Just a data-oint: Formula 1 cars use 304.8 mm front tires and 348mm rear on magnesium wheels that are almost exactly the same width. 1521 lbs minimum weight with driver.
    sirele
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    16 Dec 2013 12:53 PM
    Is there such a thing as too wide tire? Yes!
    Many reasons to name. Autox is not F1. One lap performance is different than wheel to wheel racing. Weight, gearing, suspension design, rotational/unsprung weight, surface, course design, weather conditions, aerodynamics, drive train layout, vehicle width (smaller is better in autox) etc all are important when making a decision on what tires to use.
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