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Thread: 949 Racing 15"x11" wheels

  1. #11
    Gluon
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    What did you end up running in front (wheel/tire)? Rear sounds like 949 15x11" w/ Hoosier A7 275/35R15

    Quote Originally Posted by Frank Orozco View Post
    So excited to get these! Will be mounting 275 wide Hoosier A7's on them shortly.





    To help any other Ariel atom owners...

    -longer wheel studs do not seem to be needed
    -purchase the hubcentric ring from 949 so that you don't just rely on lug-centric centering
    -these clear all components on both the front and rear and look to be a great fit for the Atom
    -this is the recommended width of wheel for the A7 rubber

  2. #12
    Ion
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    I currently run 205s up front and 245s in back (A7s) on my SRA. One of these days I plan to run wider in both front and back to see if wider is faster. I tend to think they won't be because of the difficulty getting heat into even the 205s and 245s, let alone 275s and wider but there is only one way to find out for sure.

    Has anyone done any back to back testing of wider tires than spec on their SRA? If so, what did you find out?

  3. #13
    Gluon
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    What temperatures are you seeing on your A7s?

    Quote Originally Posted by Phoenix Atom View Post
    I currently run 205s up front and 245s in back (A7s) on my SRA. One of these days I plan to run wider in both front and back to see if wider is faster. I tend to think they won't be because of the difficulty getting heat into even the 205s and 245s, let alone 275s and wider but there is only one way to find out for sure.

    Has anyone done any back to back testing of wider tires than spec on their SRA? If so, what did you find out?

  4. #14
    Lepton cvjoint's Avatar
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    I got faster and faster up to 245 rear, then jumped to 355 rear. So far I've only tried the 355's in 40* and 50* weather and only once but they were slower. I might run these combos, just bought my own pyrometer:
    205/225 up to 55* or wet (these are my Hoosier H20)
    225/245 up to 70*
    245/355 70* and up.

    My SRA is stock. The optimal tire is going to be different depending on power, aero and ambient temperature. I got a set of 245" in A7 compound in the rear up to 170* before and that's beyond optimal temps.

  5. #15
    Ion
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    Quote Originally Posted by aoysgelt View Post
    What temperatures are you seeing on your A7s?
    I'm lucky if I get 150 - 160 degrees.

    Quote Originally Posted by cvjoint View Post
    I got faster and faster up to 245 rear, then jumped to 355 rear. So far I've only tried the 355's in 40* and 50* weather and only once but they were slower. I might run these combos, just bought my own pyrometer:
    205/225 up to 55* or wet (these are my Hoosier H20)
    225/245 up to 70*
    245/355 70* and up.

    My SRA is stock. The optimal tire is going to be different depending on power, aero and ambient temperature. I got a set of 245" in A7 compound in the rear up to 170* before and that's beyond optimal temps.
    355s! Holy cow! There must come a point where wider isn't better and my guess is that is beyond the point.

    I called Hoosier a while back and was told that optimal temp is 180 - ? I forget the upper range and it doesn't seem relevant, anyway, because there seems no chance of overheating the tires.

  6. #16
    Lepton cvjoint's Avatar
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    Quote Originally Posted by Phoenix Atom View Post
    355s! Holy cow! There must come a point where wider isn't better and my guess is that is beyond the point.

    I called Hoosier a while back and was told that optimal temp is 180 - ? I forget the upper range and it doesn't seem relevant, anyway, because there seems no chance of overheating the tires.
    Well, the only way to get the stickiest compound above 245" in 15" is to go to 355". The softer the better and I got a soft spot for steamroller tires!

    A7 optimal temp is 110* to 140*. It's the R7 that wants 180* to 200*. At 180* the A7 is fairly greasy but still derivable, probably ~1 second slower a lap.

  7. #17
    Ion
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    According to the hoosier engineer I spoke with, 180 and up (don't recall the upper limit of ideal temp range) is optimal. I'm not sure where your getting your numbers if Hoosier is saying 180. On the other hand, the engineer noted that he hears reports from autocrossers that the tires work fine at much lower temps.

    Quote Originally Posted by cvjoint View Post
    Well, the only way to get the stickiest compound above 245" in 15" is to go to 355". The softer the better and I got a soft spot for steamroller tires!

    A7 optimal temp is 110* to 140*. It's the R7 that wants 180* to 200*. At 180* the A7 is fairly greasy but still derivable, probably ~1 second slower a lap.

  8. #18
    Gluon
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    Here is what I found from Hoosier manual

    Tire Temperature Recommendations
    For best performance the expected temperature range will vary from track to track. Generally, optimum traction will be generated when the pit lane temps show 180-200 degrees for the R7 in Roadrace applications, and 110-140 degrees for the A7 in an Autocross application.



    Quote Originally Posted by Phoenix Atom View Post
    According to the hoosier engineer I spoke with, 180 and up (don't recall the upper limit of ideal temp range) is optimal. I'm not sure where your getting your numbers if Hoosier is saying 180. On the other hand, the engineer noted that he hears reports from autocrossers that the tires work fine at much lower temps.

  9. #19
    Ion
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    Quote Originally Posted by aoysgelt View Post
    Here is what I found from Hoosier manual

    Tire Temperature Recommendations
    For best performance the expected temperature range will vary from track to track. Generally, optimum traction will be generated when the pit lane temps show 180-200 degrees for the R7 in Roadrace applications, and 110-140 degrees for the A7 in an Autocross application.
    Good to know. I stopped trying get 180 into my A7s long ago because I couldn't and it turns out the temps I'm getting are right where they should be...I learn new stuff every day.

    But I sure wonder about what I recall the Hoosier guy telling me. I misunderstood him, he misunderstood me or who knows. I'm just glad to know the 110-140 info.

  10. #20
    Lepton cvjoint's Avatar
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    Quote Originally Posted by Phoenix Atom View Post
    Good to know. I stopped trying get 180 into my A7s long ago because I couldn't and it turns out the temps I'm getting are right where they should be...I learn new stuff every day.

    But I sure wonder about what I recall the Hoosier guy telling me. I misunderstood him, he misunderstood me or who knows. I'm just glad to know the 110-140 info.
    The Hoosier rep likely thought you were talking about R7 either because it's stock on SRA or because that's the road course choice for most circuit racers. Almost all production cars overheat A7 on road course over 20 min stint.

    You can check SCCA boards and similar to confirm. Folks starts spraying the A7 once in reaches 140*.

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