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Thread: Avon ACB10 Tires

  1. #11
    Junior Member
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    Originally posted by Zac:
    <BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Nath_01:
    Why do you say they make your car drive like crap? What experiences have you had with soft compounds?
    There are two problems with a "soft" compound.

    First, cornering stiffness is going to decrease as compound stiffness decreases. FSAE cars tend to spend a lot of time at high slip angles so that may not be a huge deal in terms of lap time, but it can result in reduced steering precision (you'll need a better driver to go fast) and increased tire drag (costing you fuel economy and lap time).

    Second, the "soft" compounds that a lot of tire manufacturers will use for autocross, hillclimb, or rain tires are super hysteretic. They will come up to temp really fast, but they can also suffer from reversion and begin to grain during long stints in warm weather. This can result in large balance and driveability changes after a couple laps. My experience is that a lot of the "soft" tires are faster out of the gate but will fall off pretty hard at the end of endurance once the car becomes a handful to drive.

    Also, I would highly recommend that you get it out of your head that there is a strong relationship between compound stiffness and grip. </div></BLOCKQUOTE>

    The compound being "soft" or "hard" has nothing to do with the tire's "spring rate". It is a totally independent characteristic.

  2. #12
    Originally posted by ffrgtm:
    <BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Zac:
    <BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Nath_01:
    Why do you say they make your car drive like crap? What experiences have you had with soft compounds?
    There are two problems with a "soft" compound.

    First, cornering stiffness is going to decrease as compound stiffness decreases. FSAE cars tend to spend a lot of time at high slip angles so that may not be a huge deal in terms of lap time, but it can result in reduced steering precision (you'll need a better driver to go fast) and increased tire drag (costing you fuel economy and lap time).

    Second, the "soft" compounds that a lot of tire manufacturers will use for autocross, hillclimb, or rain tires are super hysteretic. They will come up to temp really fast, but they can also suffer from reversion and begin to grain during long stints in warm weather. This can result in large balance and driveability changes after a couple laps. My experience is that a lot of the "soft" tires are faster out of the gate but will fall off pretty hard at the end of endurance once the car becomes a handful to drive.

    Also, I would highly recommend that you get it out of your head that there is a strong relationship between compound stiffness and grip. </div></BLOCKQUOTE>

    The compound being "soft" or "hard" has nothing to do with the tire's "spring rate". It is a totally independent characteristic. </div></BLOCKQUOTE>

    Regarding the "spring rate" of cornering stiffness, I'm going to have to disagree with you big time on this one.
    Colorado FSAE | '05 - '07
    Goodyear Tire & Rubber | '07 - '11
    NASCAR Engineer | '11 - ??

  3. #13
    Originally posted by ffrgtm:
    <BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Zac:
    <BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Nath_01:
    Why do you say they make your car drive like crap? What experiences have you had with soft compounds?
    There are two problems with a "soft" compound.

    First, cornering stiffness is going to decrease as compound stiffness decreases. FSAE cars tend to spend a lot of time at high slip angles so that may not be a huge deal in terms of lap time, but it can result in reduced steering precision (you'll need a better driver to go fast) and increased tire drag (costing you fuel economy and lap time).

    Second, the "soft" compounds that a lot of tire manufacturers will use for autocross, hillclimb, or rain tires are super hysteretic. They will come up to temp really fast, but they can also suffer from reversion and begin to grain during long stints in warm weather. This can result in large balance and driveability changes after a couple laps. My experience is that a lot of the "soft" tires are faster out of the gate but will fall off pretty hard at the end of endurance once the car becomes a handful to drive.

    Also, I would highly recommend that you get it out of your head that there is a strong relationship between compound stiffness and grip. </div></BLOCKQUOTE>

    The compound being "soft" or "hard" has nothing to do with the tire's "spring rate". It is a totally independent characteristic. </div></BLOCKQUOTE>

    Who is talking about spring rate? I'm talking about cornering stiffness. The number one factor in controlling cornering stiffness is the stiffness of the tread band. Individual variables that a tire designer will use to tweak cornering stiffness include: compound stiffness, tread cavity shape, tread design, tread depth, and belt angle. If you don't follow, read either Pacejka (if you want a headache) or Purdy (if you want a migraine).

    But now that you bring it up, both lateral and vertical spring rates will change with compound stiffness. It won't change as much as tweaks to either mold geometry or material lay-up, but it will have a measurable effect.

    Another caveat about tires: never assume that you're dealing with a totally independent characteristic. Tires are highly non-linear composite structures.

  4. #14
    Well, to bring this thread back from the grave: I found some old 7" FFord Avon ACB10's in our "storage" area, which will fit our wheels (had a lot of 6" FFords too narrow for our rims). Most of them don't even look too bad, or worn.

    Thus, we will be soon driving the 2011 Melbourne Uni car on said tyres. Photo below:

    Melbourne Uni FSAE 2011 car with Avon ACB10 7.0"

    The reason we're running these is that we only have 50% tread left on some new Hoosiers, and the comp set of Goodyears, both of which we would like to save for practice closer to (2012) comp. We have new drivers to train (100% new guys on the team; 100% new drivers), so to save money, we're using the FFord Avons.

    The main concern seems to be low grip, and not being able to get heat into the tyres. Well, the 2011 with the heavy wheels was 250kg, on Goodyears. The ACB10s are a LOT heavier, so add another 10kg to the whole car. Any opinions on how the car should handle? Low grip sounds fine to me (an engine guy), but not if it handles VERY different to how the good slicks will perform. And, the variation in OD (20.0" to 22.0" = 1" increase in ride height) means a rather big change in suspension stuff, I'm sure.
    Rex Chan
    MUR Motorsports (The University of Melbourne)
    2009 - 2012: Engine team and MoTeC Data acquisition+wiring+sensors
    2013 - 2014: Engine team alumni and FSAE-A/FStotal fb page admin/contributer

    r.chan|||murmotorsports.com
    rexnathanchan|||gmail.com
    0407684620

  5. #15
    Senior Member
    Join Date
    Jun 2007
    Location
    Perth Western Australia
    Posts
    211
    Rex, see my post above, we use the 6" fronts on 7" rims no worries.
    They handle a bit differently, but nothing that would detract from driver training, and maybe even some car development.
    The height of the fronts is ok to.

    Pete

  6. #16

  7. #17
    I can only reiterate Luniz's comments, as we had the exact same problem in 2009, except we were running 6" all round, unlike Kiel's 7-8" beasts. I remember some jaws dropping at the state of our rubber when we pulled into the fuel station! This was the only time we'd had a major problem though, in a very high track-temp enduro. Other than that, the A45 is an awesome FS tyre as its superb right out of the box, and gave us P2 in skidpad and accel that year.
    Regards,


    Lee Stretch
    UHRacing Alumni
    www.racing.herts.ac.uk

  8. #18
    Hello!

    Just went for our first drive on Avon ACB10 (7" Formula Ford tyres all round). There was a lot less grip, understeer, and lots of tyre squeal. Our drivers liked to use the throttle to get the rear tyres to spin and get the car pointing faster. Use the same tyre pressure as normal Hoosiers/Goodyears (around 10-11psi). Got "warm" 40-50C on a nice sunny 24C day in Melbourne.

    Bonus: you can lock up for 10m, and not flat spot the tyres. They get warm, but not sticky. We drove on smooth concrete though.

    Photo album on fb: MUR 2012: Flat Sump First Drive/Avon ACB10 First Drive (FFord)

    Overall: a really good way to get new drivers some seat time without the cost of using up valuable rubber. With Valvoline as oil sponsor, it's only costing us fuel money to buy Caltex E85.

    And now for some videos: Driving on Avon ACB10 7" Formula Ford tyres in an FSAE car

    Another video uploaded (YouTube): MUR 2012: Formula Ford Avon ACB10's on an FSAE car

    Even more videos: MUR 2012: More Avon ACB10 drifting in an FSAE car with Hashan
    MUR 2012: FSAE Flat Dry Sump testing at Essendon Airport
    Rex Chan
    MUR Motorsports (The University of Melbourne)
    2009 - 2012: Engine team and MoTeC Data acquisition+wiring+sensors
    2013 - 2014: Engine team alumni and FSAE-A/FStotal fb page admin/contributer

    r.chan|||murmotorsports.com
    rexnathanchan|||gmail.com
    0407684620

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