Ideal tyre (tire) temps.

Discussion in 'Motorbike Technical Discussion' started by Bummers, Jun 2, 2005.

  1. Bummers

    Bummers Guest

    Does anyone know what the ideal temperatures are for m/c tyres for
    racing purposes?
    Does it vary Dependant on brand/construction?
    Can it be measured with an electronic surface temp probe adapter thingo
    for a multimeter? Or do you need a specific tyre temp gauge (gage - for
    the Yanks/Mercans)?
    What temp. do tyre warmers operate at?

    All these questions?
    Bummers, Jun 2, 2005
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  2. Motorsickle tahrs. Them's those round black donuts what keeps yer
    chromed rims from getting all scratched up, right? ;-)

    Street tires will optimally run from 122 to 158 degrees F. Race tires
    will run from 175 to 250 degrees F. Some manufacturers are supplying
    "green" rubber to the racers. "Green" rubber isn't completely cured at
    the factory, it's still soft and weak. But it sticks to the track well.
    The rider is actually curing the tire as he rides his warm up laps and
    the first race laps. When he feels the tire "come in", it has the most
    traction it's ever going to have. He can get onto the power early at
    higher lean angles. Now he can race competitively as long as the tire
    lets him put all his power to the ground.

    When he feels the tire "go off" it has less traction, he can't use the
    throttle while leaned over. Then the special oils used to extend the
    dynamic range of flexibility of the rubber in the tire begin to rise to
    the surface. The tire feels greasy. If you examine a tire that been
    through a few heat cycles and has cooled off, it looks blue, and it is
    done for, as far as racing goes. Sell it to a squid so he can brag to
    his buddies that he'd chewed up the tire like that on a race track the
    previous weekend...

    If you don't believe there is any oil in your tires, google up
    "extender oil +cold process rubber"...
    Sure. All manufacturers have proprietary rubber compounding "secrets"
    but they are all experts, and they can figure out what the other guy is
    mixing in his rubber kettle and duplicate it if the other guy's tires
    are winning more races.

    They all have their own ideas about carcass flexibility in the
    crown and sidewall areas of the tire, too...

    Riders expect the crown of the tire (the area underneath the tread) to
    have uniform stiffness at all lean angles for consistent feel.

    (But pointy triangular race track tires will have a different feel at
    small lean angles, or straight up, than they feel while leaned over,
    that's why you see riders stick a knee out and then scramble over to
    the wrong side of their machine before turning into a corner.)

    The sidewalls of different tires are taller or shorter, and they are
    stiffer or more flexible according to the weight of the motorbike and
    the way it's intended to be ridden and how rigid the chassis is when it
    hits bumps while leaned over to the max...

    The suspension engineers are using the sidewalls as a rubber spring to
    absorb those out-of-plane bumps that the suspension system can't
    handle. The out-of-plane suspension load problem is so bad that chassis
    engineers keep redesigning their chasses to be less rigid. You may hear
    that the latest Honda chassis has been "improved" in terms of torsional
    rigidity, but they are saying which direction they are "improving" it
    in, more rigid, or more flexible...

    Then there's the weight business vs. responsive turn-in
    characteristics. Bigger 4-stroke motorcycles can be porkers in terms of
    weight, but the riders still want agile handling out of their
    elephant-on-wheels. The engineers have been building bigger, more
    powerful motorbikes for decades, giving us great big rear tires that
    can handle the power without overheating themselves and melting, but
    the tiny front tire looks like it belongs on a motorscooter...

    That front tire has to have a very rigid sidewall in order to support
    the front end of some porky literbike that might weigh 750 pounds with
    a 250-pound rider that has a 46 inch waistline. This rider sits around
    in a cubicle at work, typing to internet newsgroups all day, drinking
    coffee and eating donuts, and when he goes out on his Holy Track Day,
    he expects that motorscooter tire on the front of his Hiya Buzzard to
    hold his engine off the ground while he does terrible things to it, and
    maybe he even complains about how fast it wears out and how harsh that
    poor overworked tire rides when he's on a freeway. Jeez!

    Sammler motorbikes are so much more gentle on their tires, the American
    Motorcyclist Association has made 600cc the displacement limit for
    Formula Extreme class that replaces the old 1000cc class in US
    superbike racing...
    Tire temperatures are measured with a device called a "pyrometer". Car
    temperatures will vary from edge to center to opposite edge and can be
    interpreted as to optimum pressure and whether the camber and toe-in is
    set right...

    But motorbikes run on one side of their tires more than on the other,
    and the less used side may be too cold to produce optimum traction
    while the other side is overheated and getting "greasy" feeling...
    Probably 175 degrees and up...
    krusty kritter, Jun 2, 2005
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  3. Bummers

    Bummers Guest

    Many thanks kk,
    Think you answered tyre questions I had yet to ask.
    Bummers, Jun 2, 2005
  4. Bummers

    Bummers Guest

    I found another - how quickly do the tyre temperatures drop?
    If it takes 1 min. to get from track to pit lane before measuring tyre
    temp - do I need to make an allowance for the drop off before measuring?
    Bummers, Jun 2, 2005
  5. Check out this Bridgestone .pdf file. It's very instructive even though
    it dates back 20 years...

    If you're planning to go motorbike racing, get used to going to your
    local race track every race weekend and hang around the paddock talking
    to everybody that races in the class you're going to be riding in. If
    you listen to people and don't try to impress them with what you know,
    they will open up and tell you everything....

    Don't expect the class champion do do that, he needs to keep some speed
    secrets to himself so he can keep winning. But a lot of the guys just
    want to compete and ride close to each other and ride hard and it's
    amazing how much they will tell you if you act humble and just listen
    instead of beating your own drum...

    And, when you go to the race tracks, hang around the tire distributors'
    trucks and ask questions about what the popular tires are this season.
    They will usually have a chalkboard with all the recommended tire
    pressures for the most popular tires...
    krusty kritter, Jun 2, 2005
  6. Bummers

    Bummers Guest

    It'll be from a compatible era of when I raced last!
    Bummers, Jun 2, 2005
  7. I realize everyone is talking about pressures/temps for track use,
    but I think it bears noting: street pressures should always be
    higher, esp. on front wheels, to protect the rim against deforming.
    City streets bite, and none are worse than ours in San Francisco.

    On a reliable, smooth surface like a track, I prefer the lowest
    pressure possible without squirm. This tends to reduce warm up
    time and increase the size of the contact patch. But this will
    depend on how compliant your suspension is, too.
    Michael Sierchio, Jun 2, 2005
  8. Bummers

    Bummers Guest

    You may have meant a smooth *street* surface like a track but if
    pressures are "just above squirm" won't they overheat easily & not
    provide max. traction?
    Bummers, Jun 3, 2005
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