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Thread: Wheel size and its effect on grip and traction Hoosier R7

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    Default Wheel size and its effect on grip and traction Hoosier R7

    I've always wondered to what degree does wheel size (diameter) effect grip. All things being equal, which setup do you guys think will yield most grip? Most traction? Break away characteristics?

    275/45r16 Hoho R7 on 16x11
    275/40r17 HoHo R7 on 17x11
    275/35r18 HoHo R7 on 18x11

    All the same? 18's most peak grip? 16's best for traction/break-away? 17's best all around? It depends? They're all the same?

    -Dino
    Last edited by Dino Antonov; 12-06-2017 at 11:38 AM.

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    http://www.trackhq.com/Banners/yellowsitesponsor.gif emilio700's Avatar
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    Our general rule of thumb with radials is to size the wheel equal to or slightly wider than the actual tread width.
    Not casing width and not necessarily whats published on the mfr website. Hoosier site tread width numbers are generally accurate. Hoosier always recommends a wheel too narrow for the tire though so basically, ignore what they publish on that.

    We find the 275/35/15 A7 to be fastest on an 11" wheel. Significantly so.

    We run the 205/50/15 on a 9" as it's tread is about 220mm wide at the shoulders (8.66")
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    Emilio,

    Thats what I've learned to know as well.

    Given the 3 tire sizes I listed, all similar or same compound, same overall height (~ 25.6") same 275mm section width, is it safe too assume they will will all yield similar grip regardless whether they're 16, 17, or 18"?

    Quote Originally Posted by emilio700 View Post
    Our general rule of thumb with radials is to size the wheel equal to or slightly wider than the actual tread width.
    Not casing width and not necessarily whats published on the mfr website. Hoosier site tread width numbers are generally accurate. Hoosier always recommends a wheel too narrow for the tire though so basically, ignore what they publish on that.

    We find the 275/35/15 A7 to be fastest on an 11" wheel. Significantly so.

    We run the 205/50/15 on a 9" as it's tread is about 220mm wide at the shoulders (8.66")

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    Who ever wrote that article sounds like they knew what they're talking about


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    Assuming the same overall tire diameter for all three wheel diameters the grip should be roughly the same. Generally speaking the shorter the sidewall, the more sensitive the car will be to set up. Camber setting, spring rates what have you.
    If they are not the same overall diameter then the largest diameter will give you the biggest contact patch, thus the greatest mechanical grip. Everything else being equal.
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    Just looked it up and the 275/35-18 R7 is 10.3" wide. So a 10.5-11" wheel would be far better than 10" and I agree with emilio that 11" wheel would get more grip out of the tire than anything smaller. I would NOT put a 10" on it if I didn't have to.

    Generally, if you maintain the same OD, the tire with the larger wheel (275/35-18) will be lighter than the tire with the smaller wheel (275/45-16). Lighter tire = lower rotational mass, which = lower gyroscopic effect, better braking and acceleration, etc... Also the smaller sidewall will be more responsive and generate more grip due to the contact patch maintaining a better shape than a tire with a larger sidewall.
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    I agree, my experience in testing with S2000 is that tire being equal, grip went up with wheel width, I tested a control tire (255/40r17) with everything from 8.5-10" and the 10" was by far the best.

    The car in question now is an old 911 which makes it difficult to run an 11" wide wheel, may be able to pull off 10.5" we'll see. I really wanted to run 275/45r16's simply because they look "right" on the car, I guess I'll need to test both 16's and 18's to see how much time the 18's are worth.

    Quote Originally Posted by Stuntman View Post
    Just looked it up and the 275/35-18 R7 is 10.3" wide. So a 10.5-11" wheel would be far better than 10" and I agree with emilio that 11" wheel would get more grip out of the tire than anything smaller. I would NOT put a 10" on it if I didn't have to.

    Generally, if you maintain the same OD, the tire with the larger wheel (275/35-18) will be lighter than the tire with the smaller wheel (275/45-16). Lighter tire = lower rotational mass, which = lower gyroscopic effect, better braking and acceleration, etc... Also the smaller sidewall will be more responsive and generate more grip due to the contact patch maintaining a better shape than a tire with a larger sidewall.

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    Why not run a 275/45-16 with a 10.5-11" wheel? The difference in diameter isn't terminal or a deal-breaker. Sure an 18" would be better but you can still make a 16" work.

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    Yup, That's more or less what I wanted to hear, I just wanted to ask the question in case somebody had data/experience showing that 16's are significantly slower.

    Quote Originally Posted by Stuntman View Post
    Why not run a 275/45-16 with a 10.5-11" wheel? The difference in diameter isn't terminal or a deal-breaker. Sure an 18" would be better but you can still make a 16" work.

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    Quote Originally Posted by Stuntman View Post
    Generally, if you maintain the same OD, the tire with the larger wheel (275/35-18) will be lighter than the tire with the smaller wheel (275/45-16). Lighter tire = lower rotational mass, which = lower gyroscopic effect, better braking and acceleration, etc... .
    I think you meant the opposite. Assume same OD and width. Smaller wheel / tire combo should always be lighter. Tire casing is the same, but wheel weight is less with smaller diameter wheel. also less rotational mass because most of wheel weights are on the outside.
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    William is right, wheel is always lighter than a tire. But wheel/tire weight by itself doesn't make a car fast. The shorter sidewall will generally be more responsive, run cooler and have a more stable tread.

    When customers contact us about various wheel widths asking which is lightest I always ask why. They always assume that the lightest wheel will be the fastest. I have to explain to them that the widest wheel/tire that the car has enough power to maintain optimum slip angle at the target speeds, will be fastest.
    That combination is usually one or more inches wider, and heavier than the one they have their heart set on. I have to explain to them that if wheel weight was the primary deciding factor in performance then racing regulations would restrict weight. But they rarely mention weight, instead they always restrict width.

    Once you have determined the optimum Wheel and Tire width for your application, then buy the lightest combination you can afford. But the width decision comes first.
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    Quote Originally Posted by bellwilliam View Post
    I think you meant the opposite. Assume same OD and width. Smaller wheel / tire combo should always be lighter. Tire casing is the same, but wheel weight is less with smaller diameter wheel. also less rotational mass because most of wheel weights are on the outside.
    Billy needs someone to read his posts before he hits send.
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    I would think its better to have a slightly heavier wheel and a slightly lighter tire as opposed to the opposite because inertia increases with the radius.

    Quote Originally Posted by bellwilliam View Post
    I think you meant the opposite. Assume same OD and width. Smaller wheel / tire combo should always be lighter. Tire casing is the same, but wheel weight is less with smaller diameter wheel. also less rotational mass because most of wheel weights are on the outside.
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    Quote Originally Posted by Dino Antonov View Post
    I would think its better to have a slightly heavier wheel and a slightly lighter tire as opposed to the opposite because inertia increases with the radius.
    That would be good, but the trouble is the wheels carry a fair amount of their weight far from the hub. Tires have a bunch of weight in and behind the part that makes contact with the road, and then have some in their sidewall. So a smaller wheel will bring more rotating mass towards the center than a taller wheel would.

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    Here is a Grassroots magazine test of 3 wheels diameter with same OD.

    https://grassrootsmotorsports.com/ar...ke-you-faster/
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    The tread of a tire is the heaviest segment of a tire and wheel combo by far. For a given overall diameter and tread width, the combo with the smallest diameter wheel will be the lightest. The combo with the shortest sidewall section will tend to offer the best overall performance however.
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