Low grip

  • Drivingforfun's Avatar
    This might be a really novice question but I've done almost zero off-road driving in my life!!

    I was manoeuvring around a gravelled car park yesterday and when I took my foot off the clutch my car seemed to wheelspin and lurch forward, almost like when as a learner I'd panic doing a hill start or something and apply too much power

    I'm assuming this is down to the power you're trying to put down vs. the grip, and the tolerance for power is changed when you're not on tarmac

    Aside from looking to confirm that or not, my question is, when driving a very powerful car, would this be likely to happen on normal tarmac? I've heard of a few UK-based Mustang owners reporting similar on the road - presumably not being used to that kind of configuration - and being told they need to be more gentle with the pedals (which is what I found on the gravel). Just wondering if it's roughly similar principle, to try to educate myself!

    Thanks
  • 3 Replies

  • Beelzebub's Avatar
    Novice question? Not really, but you need to go back to school physics.

    The force needed to overcome friction (in this case, between tyre and surface) is proportional to the Coefficient of Friction. In crude terms, the more slippery the surface, the lower the CoF, and hence the lower the force needed to make the wheels slip.
  • olduser's Avatar
    In practical terms, on a low grip surface, the best strategy is to leave the engine idling, and gently/slowly let in the clutch.
    On a gradient, where a tick over just produces a stall, the trick is to let the throttle follow the clutch as apposed to the usual, throttle then clutch.

    This way you have the minimum force at the tyre contact patch, another way of achieving the same thing is to use a high gear, as the 'force' is torque, and the gearbox is a torque transformer, low gears multiply torque high gears = less torque, top gear is about 1:1 unless there is some overdrive.

    Most high powered cars will spin their wheels, certainly in lower gears if the throttle is not used sympathetically.
    Electric cars have maximum torque at zero motor revs so the throttle has to be used with care.
    Last edited by olduser; 02-02-25 at 11:38.
  • Rolebama's Avatar
    Drivingforfun: This is why different tyre tread patterns exist. The best I believe are classified as all-weather. The worst, for our climate are the semi-slicks.
    On a similar note: This is also why lorries shred the road surfaces. When pulling away the torque at the wheel is greater than necessary to overcome the inertia of the vehicle, and something has to give.