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Last Post 12 Oct 2015 10:24 AM by  47CP
Whats a better racing slick? Bias-ply vs Radial ?
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TavernCustoms
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09 Nov 2013 05:48 AM

    So I'm trying to figure out what racing slick holds more grip and what slick is better. bias ply or radial, lets say Hoosier to avoid brand comparison.

    I am new to racing so forgive me if I ask questions.

    rjohnson999
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    09 Nov 2013 11:05 AM
    If you're new to racing it won't matter.  You're not experienced enough to be able to benefit from any difference.  The smart thing to do is find the cheapest tires so you can spend more of your money on track time.
    TavernCustoms
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    09 Nov 2013 04:46 PM
    I totally agree I was just curious
    Lynn
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    09 Nov 2013 11:54 PM
    Bias ply is easier to learn with. They have a more gradual transition from grip to no grip.
    47CP
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    10 Nov 2013 11:58 AM
    It really depends on the car and tire size....there are different answers for different tires and cars.

    DaveW
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    11 Nov 2013 02:05 AM
    lets say, same size tire, same car, awd
    TavernCustoms
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    11 Nov 2013 02:09 AM
    Posted By Lynn on 09 Nov 2013 11:54 PM
    Bias ply is easier to learn with. They have a more gradual transition from grip to no grip.

    the question is, what one holds more grip.  


    Scootin159
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    11 Nov 2013 09:14 AM
    I think what Dave's saying is that you won't find a solid answer - on some cars bias ply will provide more grip, while on other cars radial tires will provide more grip. It's not even something that you can say depends on if you have FWD, RWD, AWD, nose heavy car, rear heavy car, light car, high horsepower, low horsepower. It all comes down to what the car's suspension geometry (not design, geometry), alignment values and possibly then weight distribution, tire sizes and horsepower.
    47CP
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    11 Nov 2013 10:03 AM
    the question is, what one holds more grip.


    I think the question is too vague.

    Are you measuring which tire has the highest coefficient of traction? You would need a tire engineer to answer that.

    But, the tire that produces the highest grip number may not be the fastest around an autocross course or race track.

    Besides that, on specific cars, radial versus bias is a complex topic. For example, in CP, Goodyear bias has been winning the class for the last several years when Hoosier bias was dominant before. But, I have been involved in testing of GY vs Hoosier and the HoHo produces higher avg. g numbers, but is harder to drive, and therefore slower.

    Goodyear radials are dominant on GT-1 Road Race cars, but no one has had much luck with radials in CP, either GY or Hoosier. For years, the story was that the radial carcass just didn't like the heavy transitions of autocross. But, in August, Hoosier tested some new radials with some construction changes and (most importantly I think) a softer compound (A6 Compound) and they seem very good.

    All of those variables are basically on the exact same car(s).

    DaveW
    davebs14
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    14 Jan 2014 10:20 PM
    I'll toss in some irrelevant info

    On my miata I ran a few different tires (most were take offs) on my 13x9s. A6s, Goodyear 20x9s, Hoosier 20x9 and Cooper 180550-13s. The Coopers were radial slicks off the fromt of LMP2 cars. They worked best on my car IMO. They were more responsive and had better turn in. Forgiving? Somewhat (much like a radial DOT tire IMO). As forgiving and willing to slide as the bias hoosier or GY? nope.

    Bias also require a different setup. The old Hoosier Autocrosser (DOT bias ply tire) used to be THE TIRE in CSP. They were also great because they worked with less camber than the DOT tires at the time and drove with a good slip angle. When the new hoosier A3S03 came on the market the game changed. Since then SP has been a radial class. And the Autocrosser is gone. The Street TD still exists but things seem to be going the radial route.

    One big difference is weight. I'd bet the bias ply is 20% lighter in construction. So that's something as well.
    t walgamuth
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    23 Aug 2015 10:48 AM
    Anybody running Hoosier radials in D mod?
    racingfool
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    23 Aug 2015 03:42 PM

    Posted By t walgamuth on 23 Aug 2015 10:48 AM
    Anybody running Hoosier radials in D mod?

    I'm guessing not many.
    9" or wider in a radial will be at least 23" tall.
    Don't D-mods like those wide 20 and 21" tall bias ply slicks?
    t walgamuth
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    23 Aug 2015 05:05 PM
    There are hoosiers that are 8.7 wide at the tread and 20.9" tall and 9.7 wide and 20.9" tall. I think that is close enough to the current size to work. We currently are running 10 x 22" on the rear and 20 x 9 on front. I liked the radials I used to run but am not eager to buy a thousand dollars worth to experiment. We'd have to change the rear end ratio of course.
    racingfool
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    23 Aug 2015 05:25 PM

    Posted By t walgamuth on 23 Aug 2015 05:05 PM
    There are hoosiers that are 8.7 wide at the tread and 20.9" tall and 9.7 wide and 20.9" tall.

    I can't seem to find them.

    https://www.hoosiertire.com/rrtire.htm

    I like radials and would give them a try if the size is right.

    Might need a set-up change and perhaps a little different approach to driving.
    t walgamuth
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    23 Aug 2015 06:25 PM
    I found them at tire rack.
    t walgamuth
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    23 Aug 2015 06:25 PM
    a7 s.
    B17overhead
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    10 Oct 2015 02:00 PM
    I think the most convincing data point is the CSP example just mentioned. Once people started running that radial in the 13" CSP size, any former top runner with the bias ply was simply non-competitive Nationally.

    That said, as the absolute car weight goes down toward small formula car weights, the advantage of a radial diminishes. At FSAE weights and event formats, no advantage to radial seems to solidly exist yet.

    While all the top unlimited class Brit Hillclimb drivers have finally now all switched to radial slicks on all 4 corners, the advantage wasn't significant.

    Just a few years ago, all-out hillclimb records were still being set by front radial-rear bias combinations and even some all bias ply setups.

    Hoosier radial slicks aren't available in R25B except in one or 2 rare cases, so I reckon that you may have trouble finding solo compound availability using their radial slick.

    Avon makes a wide range of radial slick compounds in everything from too soft to too hard. The only oddity you would have to deal with is that radial fronts tend to be taller than most of their bias ply counterparts. The really good radial fronts in the 9 to 10" wide category are 21.5" tall.

    The Avon compounds used by the solo guys who won these classes: AM/BM/DP/EM at Lincoln in 2015 on luke-warm to hot days were in most cases, road race compounds A53 or A11.

    That means you might be able to try out high dollar road racing team used tires for free, if you can find a kindly team manager.
    26B
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    11 Oct 2015 03:19 PM
    Usually there's a wider radial than bias-ply selection (at least for my car (BRZ) there are far more radial-options available).

    Does anybody run Avon A50, A49 or 379 compounds or are these considered too soft on a conventional car (non-formula) even in Autocross? And do people spray racing-slicks and if so under what circumstances (compound, weather)?
    http://www.avonmotorsport.com/resou.../compounds
    (I live in Europe and I'm just curious what Americans run. I know of people who run A53 and 379 in our slaloms, but I'm not sure about the other compounds. Also, the Michelin S5B has been very popular in our slaloms. Many people are also running the Yokohama A005 Super-Soft, it lasts longer than the Avon's and Michelin's but it is slower.)

    Also, have you guys considered Hankook F200 at all (or is this tire not available in the US)?
    B17overhead
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    11 Oct 2015 04:40 PM
    Those compound numbers like 379 and A49 are ones that I haven't seen widely available in mod class 13" tires.

    A dealer can tell you for sure and may have to call England. There is no internet data from Avon themselves on all the possible combos. Dealers will list what they stock or can get, but it isn't everything. Roger Krause Racing does have a long list of tires and compounds in both bias as well as radial on his site.

    A53 seems close to R25B Hoosier, maybe a tiny bit harder and A11 a tiny bit harder still. A53 is a popular road race front to couple with an A11 rear on mid engine cars.

    A15 is a little softer than R25B and A94 is softer still, but hard to tell the difference from A15. Some say A94 holds up better than A15.

    Spaying and icing down is common to make "too-soft" compounds live and work on a hot course.

    67 degree air temp at a fairly grippy concrete site and 45 s runs is a rough guideline to a crossover from A15/A94 over to A11, A53 or Hoosier R25B.

    Length of the course, track surface texture, and car weight vs. tire size are additional factors. Add to that handling peculiarities like a lot of understeer or oversteer and you will heat a compound more on that end of the car.
    26B
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    12 Oct 2015 07:00 AM
    Thanks.
    I was wondering what the guys with BRZ's, RX-8's, 370z's, Evo's, M3's, Corvette's, 911's are running (since these would usually require rims which are at least 17" in diameter).
    Would they go as soft as A15 at all or is the A53 the softest choice? (I remember reading that in colder states people would run the V710 instead of the Hoosier A7, because the Hoosier would not work well at colder temperatures. Is this also the case with the Avons (tire choice is depends on the region)?)
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