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Thread: SRA - data/numbers to keep an eye on on track?

  1. #11
    Ion
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    CVJOINT - can you summarize what size rims and tires you are using. I looked into some of the FA type slicks a while back and the sizing just didn't seem to work - at least not with rims I have.

    So you have been running H2Os in the dry (the cold and dry)? How has that worked out? How do they wear?

  2. #12
    Lepton cvjoint's Avatar
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    Quote Originally Posted by argonaut View Post
    CVJOINT - can you summarize what size rims and tires you are using. I looked into some of the FA type slicks a while back and the sizing just didn't seem to work - at least not with rims I have.

    So you have been running H2Os in the dry (the cold and dry)? How has that worked out? How do they wear?
    15" wheel x 10" wide front Keizer - Formula Atlantic front from Hoosier or Avon
    15" wheel x 14" wide rear Keizer - Formula Atlantic rear from Hoosier or Avon
    15" wheel x 7" wide front stock - 205 section Hoosier H20
    15" wheel x 7" wide rear stock - 225 section Hoosier H20 (there are two versions based on different diameter, I don't know which one I have)

    I run stock wheels on wets front and back when it rains.

    I run stock wheel on 225 section H2O on the front and the Formula Atlantic front on the back when it's really cold. This is faster than the full Formula Atlantic set up to ~65* ambient.

    I run the full Formula Atlantic set when it's 65* or more out.

    The H2Os work great in the dry. I even used them on a hot day when I had a blowout on the rear. They don't blister, they don't overheat, and they last a very long time if used on the front. Anything up to 245 section is going to be used in 4-5 track days if you run soft compound R25B, H2O, or A7. Running wider than 245 rear will increase longevity substantially. My 355 section Formula Atlantic rears lasted me just over 50 heat cycles but when I used the 245 section fronts on the rear they lasted half of that.

  3. #13
    Gluon
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    @cvjoint, do you mind sharing your camber, ride height, and toe in/toe out settings?

  4. #14
    Lepton cvjoint's Avatar
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    Quote Originally Posted by texevora View Post
    @cvjoint, do you mind sharing your camber, ride height, and toe in/toe out settings?
    Credit goes to MadMaxAtom for optimizing alignment using Formula Atlantic slicks. Tires heat up optimally side-center-side so I didn't see any reason to run something different. I do run slightly lower psi than he does but otherwise it's the same.
    https://www.arielatomchat.com/forums...html#post22408

  5. #15
    Gluon
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    It seems like the availability and sizing of the FA slicks has been in constant flux the last few years based on some of the recent & older posts on the forum. I'd hate to invest in new wheels and then find out that Hoosier decided to stop making the size/compound that I need. I figure the A7/R7 compounds and sizes are more readily available and less subject to discontinuation by Hoosier's FA offerings. Not sure if that's an erroneous assumption? With that in mind, I'd welcome outside opinion on what I'm thinking of getting:

    HOT WEATHER (+2" wider front wheels, +4" rears)
    front wheel: 949Racing 15x9, +36 offset - 15x9 6UL
    front tire: 245/40/R15, Hoosier item #46522 in their 2019 catalog - https://www.hoosiertire.com/assets/C...cing-Specs.pdf, in A7 or R7 compound
    rear wheel: 949Racing 15x11, +20 offset - 15x11 6UL
    rear tire: 275/35/R15, Hoosier item #46536, in A7 or R7 compound
    rear tire diameter - front tire diameter = 0.0" vs +1.0" stock SRA

    COOLER WEATHER Option 1 (reuse existing front SRA wheels, +2" on rear wheels)
    front wheel: stock SRA 15x7 wheel
    front tire: 225/45/R15, Hoosier item #46511 in A7 compound
    rear wheel: 949Racing 15x9, +36 offset
    rear tire: 245/40/R15, Hoosier item #46522 in A7 compound
    rear tire diameter - front tire diameter = +0.2" vs +1.0" stock SRA

    COOLER WEATHER Option 2 (wider wheels, +2" front, +4" rears)
    rear wheel: 949Racing 15x9, +36 offset
    rear tire: 245/40/R15, Hoosier item #46522 in A7 compound
    rear wheel: 949Racing 15x11, +20 offset
    rear tire: 275/35/R15, Hoosier item #46536 in A7 compound
    rear tire diameter - front tire diameter = 0.0" vs +1.0" stock SRA
    Any feedback/opinions welcome, especially if any of the above is known to be outright not compatible/feasible with stock SRA hardware.

    Also, are you guys who are going with different sized wheel/tire packages recalibrating your Dash2 to compensate for wheel diameter changes? With the combinations contemplated above i'd be up to 0.2" taller in front tire diameter vs stock, and up to 0.8" shorter in rear tire diameter vs stock. Not sure which wheel (or wheels) the Dash2 calculates speed from, but I'd imagine I'd need to adjust the settings to get an accurate speed reading if i change tire diameters.

    Appreciate all the insight from everybody. Having so few fellow SRA owners and a lack of Internet resources elsewhere makes all of your first-hand knowledge extremely helpful to me.

  6. #16
    Ion
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    Are you certain the 949 wheels will clear the brakes? For some reason I have it in my mind that they wont.

    I have a pair of Enkei RPF1 16x8 and they do clear the brakes (the 15x7 Enkei's do not).

    Regarding re-programming the Dash - I now have an AiM MXS dash in my car and it gets speed from the GPS, not a wheel - so its not an issue for me. What will be a problem is the gear calculation (displaying gear number on the dash) - changing wheel diameters will potentially affect that. But luckily the AiM system is exceedingly easy to re-program. Are you certain the RaceTechnology dash is using wheel diameter to calculate speed?

    Regarding your tire choices for cold weather: At the moment I prefer the 205 front and 225 rear stock combination best - at least with R7s. Just can't get enough heat in the bigger tires to generate much grip. But of course using A7 or FA tires may be different.

    By the way - the 'stock' SRA wheels are D-Force LTW5 - a wheel that is commonly used in Spec30 series (BMW E30 M3). Just in case you every need a new set of stock rims.

    Agree on the lack of info regarding Atoms on track. My past track cars have been Mustang, Miata and Corvette. All of them are really well supported by aftermarket, forums and fellow participants at events. It was a shocker for me that the Atom is so poorly supported - I should have expected it but all the same, its a startling difference - nobody seems to know $h!t about them.

  7. #17
    Gluon
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    @argonaut - on the wheel clearance, I had assumed/hoped that with the spacers 949 sells, it would. I also thought i had seen another post elsewhere on the forum that they do, but i could be wrong. Good to know on the LTW5 wheels, it looks like they are +25 offset. If anybody has knowledge of whether the 949 wheels I spec'ed above do in fact clear the stock SRA calipers, would love to hear it!

    On the wheel speed calculation, yes it's coming from a wheel speed sensor. I've been playing around with the Dash2 software and it looks like there's a section where you can program the number of pulses per kilometre, which i'll need to calculate/back into if/when I pull the trigger on these non-stock wheels/tires.

  8. #18
    Lepton cvjoint's Avatar
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    Quote Originally Posted by texevora View Post
    It seems like the availability and sizing of the FA slicks has been in constant flux the last few years based on some of the recent & older posts on the forum. I'd hate to invest in new wheels and then find out that Hoosier decided to stop making the size/compound that I need. I figure the A7/R7 compounds and sizes are more readily available and less subject to discontinuation by Hoosier's FA offerings. Not sure if that's an erroneous assumption? With that in mind, I'd welcome outside opinion on what I'm thinking of getting
    No doubt the availability of A7 will far surpass that of FA tires, especially if you are keen on having the same compound. I enjoy researching Hoosier's catalog of slicks every year and figuring out what's new in the FA world. Heck, it is fun to try different carcass and compound combinations. But there is something to say about how easy it is to get what you want in A7, plus you can learn the car more if you keep the tire fixed and can calibrate the shocks.

    I would go with the new 295 section A7 in 15" and the widest 949 wheel, I believe they make a 12" wide one. 245 front is perfect.

    For cold weather I'd go with H2O compound, it will give you the option to drive in the wet. My first track day was on R7 in the rain, spun out 4 times and couldn't challenge anyone on the roadcourse except bad Ferrari drivers and old 911s.

    I don't really bother with the speedo calibration. I might use the speedo to judge entry speeds but otherwise I datalog off the GPS anyhow. Unlike cars with traction control, stability control, ABS, 4WD, and so forth, the car really doesn't need to have the same tire diameter. It can be anything! Have fun with that one because you can. I can't stagger tires on my Cayenne because the differential would blow up, I couldn't run some slicks on the C7 Z06 because the computer would yell at me or calibrations would go out of wack. The Atom is pure freedom. Enjoy!

  9. #19
    Ion
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    Quote Originally Posted by texevora View Post
    @argonaut - on the wheel clearance, I had assumed/hoped that with the spacers 949 sells, it would. I also thought i had seen another post elsewhere on the forum that they do, but i could be wrong. Good to know on the LTW5 wheels, it looks like they are +25 offset. If anybody has knowledge of whether the 949 wheels I spec'ed above do in fact clear the stock SRA calipers, would love to hear it!

    On the wheel speed calculation, yes it's coming from a wheel speed sensor. I've been playing around with the Dash2 software and it looks like there's a section where you can program the number of pulses per kilometre, which i'll need to calculate/back into if/when I pull the trigger on these non-stock wheels/tires.
    If those wheels do require spacers - personally I'm not a fan of them - they change your scrub radius and put more stress on the hub. I'd rather go with 16 inch Enkei wheels - which I know fit. It would be good if someone could definitively say whether or not the 949s fit.

  10. #20
    Gluon
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    I've been told by other SRA owners offline that both the 15x9 and 15x11 6UL wheels should fit no problem. I think I'm going to try this as the first package:
    front wheel: 949Racing 15x9, +36 offset - 15x9 6UL
    front tire: 205/50/R15, Hoosier item #46502 (or 46501 for SM version)
    rear wheel: 949Racing 15x11, +20 offset - 15x11 6UL
    rear tire: 275/35/R15, Hoosier item #46536

    Since i'm new to the car and probably going to lock up/flatspot the tires initially, i'm going to get used Hoosiers until i get the settings all dialed in.

    While I know hubcentric rings aren't required, does anyone know what the stock SRA hub diameter is? 949 has hubcentric rings available in 56.1, 56.6, 57.1, and 59.1.

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