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Thread: How a racecar changes over a race

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    Senior Member fatbillybob's Avatar
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    Default How a racecar changes over a race

    What is happening as a racecar changes over a race? If for example a car is always best during the first 1/3 of a race what would that imply? Is that a fall off in tires? Is that shocks heating up and going away? Is it just a driver getting tired?

    What actually happens when a some drivers say "in the last 1/3 of the race the car was coming to me"? Are other guys getting tired? Is the car just getting lighter? Is the driver just getting the track dialed in? Is that a characteristic of a driver who preserves his tires to push them toward the end?

    Is the racecar really changing or is the driver changing?

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    Chest hair required Olitho's Avatar
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    I can only answer with what I experience in my car. Under the old T1 rules with 315 all the way around the car felt perfect about the first 1/3 of the race. In the last 1/3 the rear tires are getting too hot and the car starts to go from neutral balance to oversteer.

    Now with the335 and the wing even at a very low AoA the car at best can be called neutral/understeer. If the car is driven 10/10ths the whole race it definitely shifts to pronounce understeer by the end of the race. I am still working on that.
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    Senior Member slodrew's Avatar
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    You guys with the seat of your pants experience would know better than I but I'd say that's the magic of racing. Sure, after the fact, everything can be scientifically analyzed, charted, weighed, and graphed, and all of that information can be used to make predictions regarding setup and strategy. But it's the things that we can not predict or control, the affects of weather, the driver's skill and determination, and those magical moments when the man (or woman) and his (or her) car perform better than anyone thought they could, would, or should.. It's those things, the things that dreams are made of (and maybe an addiction to adrenaline lol!) that keep it interesting and keep us coming back for more.
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    Senior Member fatbillybob's Avatar
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    Quote Originally Posted by Olitho View Post
    I can only answer with what I experience in my car. Under the old T1 rules with 315 all the way around the car felt perfect about the first 1/3 of the race. In the last 1/3 the rear tires are getting too hot and the car starts to go from neutral balance to oversteer.
    My T2 car is detuned T1 with 295's square and 260 lb ballast per the rules. Your report is exactly my problem and always has been, best in the first 1/3 of a sprint race. I sort of attributed that to me getting tired and sucking. But now I'm thinking it is something else and tires seem like a great place to put the blame. We always look at lap time and test for best lap time. I wonder if we really should test for lowest race stint elaped time instead? For example lets say that tires are the issue. We know hoosier wants the tires around 40psi hot while everyone shoots for a much lower hot temp. Running a tire underinflated increases heat vs. running at recommended pressures. Perhaps starting with a higher cold temp taking away the initial speed of the tire would create less heat build-up from an underinflated tire and provide more overall lower race stint elapsed time? Is there any validity to this statement? Could we be improperly blaming the tires when the problem really is overheating the shocks? How could you test for whether the problem is tires or shocks? How much would you have to back off in laptime to cool tires enough to score fast laps at the end of a stint?

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    Senior Member bellwilliam's Avatar
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    Quote Originally Posted by Olitho View Post
    the car starts to go from neutral balance to oversteer.
    .
    That.

    That's why I always set up a car a little tighter initially in spring race.

    But in an enduro, if you know track will get stickier later (say race starts at 6pm and finish at 9pm), then you start with a neutral car.
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    In karts it's the opposite, low psi and the tires stay cooler and come in for the last 1/3 of the race, but are less grippy in the beginning. Higher starting psi and the kart is fast in the first couple laps, but quickly overheat.

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    Senior Member fatbillybob's Avatar
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    Quote Originally Posted by bellwilliam View Post
    That.

    That's why I always set up a car a little tighter initially in sprint race.
    So you actually make the car slower to start? You do this how? You add more stiffness in front bar adjustment or add more psi to the front? This initial sacrifice will make the car faster in the last 1/3rd?

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    Senior Member bellwilliam's Avatar
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    Quote Originally Posted by fatbillybob View Post
    So you actually make the car slower to start? You do this how? You add more stiffness in front bar adjustment or add more psi to the front? This initial sacrifice will make the car faster in the last 1/3rd?
    You take exact same car, same driver, same condition. It the car is neutral with say Hoosier. It will get be looser with 4 less sticky tires (say NT01).

    So a tighter car always gets looser as grip level decreases. And vise versa.

    Now to answer your question: it really depends on type of races and track condition. 2 extreme:

    Super short SPM races (we usually do 5-7 laps per sprint, 4 races per weekend). In a cooler winter weather. I will always start on neutral.

    In a 3 hour (1 set of tire) enduro stint in warm-ish weather: we always start with a tight car, so tires last longer and more neutral after first 15 minutes.

    But in a Nasa 3 hour summer event that's starts at 6pm, track actually gets grippier later in the race. So starting with a neutral car is it. .

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    Last edited by bellwilliam; 12-27-2015 at 04:52 PM.
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    Senior Member fatbillybob's Avatar
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    Quote Originally Posted by Olitho View Post
    Now with the335 and the wing even at a very low AoA the car at best can be called neutral/understeer. If the car is driven 10/10ths the whole race it definitely shifts to pronounce understeer by the end of the race. I am still working on that.
    How does a car get tighter? Is this because you have smaller front tires and you loose them as the race goes on? Need to remove the rear wing wicker bill?

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    Senior Member robburgoon's Avatar
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    Quote Originally Posted by fatbillybob View Post
    How does a car get tighter? Is this because you have smaller front tires and you loose them as the race goes on? Need to remove the rear wing wicker bill?
    Yeah, he's probably killing his fronts. Overworked tires get hotter, gain pressure, which usually makes the condition worse.

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    Senior Member JulioG's Avatar
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    If fronts are getting too hot, what about adjusting brake bias a bit towards rear during the race? I assume FWD drivers more than anyone else do this to save their front tires at some stages in the race when they're not directly fighting for position?

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    Decent idea, however FWD cars tend to be nose heavy which makes the rear tires unloaded more under braking and thus the front tires do most of the work. Things can vary with suspension geometry and weight distribution but typically the rears don't contribute much. It would be better to work on the mechanical and aero balance.

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