Grip
Richard “Scott” Clayton
You are braking as hard as you can to avoid impact with another object. And you feel the weight of your body being pressed up against the seat belt. Almost as if you were being hung from it. The coins in your shirt pocket are reaching for the windshield. You are doing everything you can to hold your head back, but your neck muscles aren’t strong enough.
Then, all of a sudden…
All of that pressure feels significantly reduced, even though you are still pushing on the brake pedal with all your might.
Your tires just lost grip of the road surface.
It’s the same when you lose grip turning or accelerating, it’s that sudden relaxation of pressure even though you are still rotating the steering wheel or pressing on the accelerator.
Commuting on the streets, we all drive well under the limits of grip. However, annually in the northern parts of the county, it’s hard to drive well under the limits of grip.
Another place where grip becomes scarce is; the racetrack.
In these environments where grip is few and far between, either forced to commute in or sought out for pleasure; is where we fine tune our driving skills.
Even though my passion is riding motorcycles on the racetrack, everyone can relate to a car. So, a car will be the example used.
To keep things as simple as possible, I’m removing nuances and specialty tires. We are going to say that your everyday typical tire has the most grip on a hot sunny day. This will be our reference standard, and call it 100% of available grip.
Next will be driving on snow, with a total amount of grip being 10% compared to that hot sunny day. And lastly, ice. With a total amount of available grip being 1%.
These percentages may sound like specific numbers but there is no science behind these numbers. As a matter of fact, I specifically chose these numbers because it is easy for people to count halves, quarters and tenths with these numbers. Asking for a quarter of 1%, 10% and 100% is easy for people who don’t like numbers. Asking for a quarter of 63% would complicate things.
100% of available grip is where you can deliver a forgotten bottle of water from the backseat to the front seats by using the brakes. On ice (1% of available grip), a mouse fart could send you spinning out of control.
Let’s go to the ice where it’s like you are walking on egg shells with the car’s controls.
Sneaking up and tip-toeing with the accelerator, steering wheel and brake; to get the car to go where you want.
On the ice with the steering wheel rotated and using all of that 1% available grip to turn, the tires are doing everything they can to turn the car.
There is NOTHING available for acceleration or deceleration.
However, if you are using 0.5% of grip to turn (think: less steering wheel rotation) and need to slow down, lifting off the accelerator could give you that other 0.5% to slow down. Where lightly applying the brakes could give you 0.6% or more, exceeding that total 1% of available grip and losing control of the vehicle.
But maybe… That 0.5% of deceleration (letting off accelerator) could give you the extra vehicular rotation you were looking for, allowing you to finish your turn EARLIER, thus allowing you to straighten the steering wheel, so now you are using 0.0% for turning and have 1% for either acceleration or braking.
I don’t need to go over the snow (10%) and the hot sunny day (100%). It’s the same as ice, except the available grip allows forces an order of magnitude larger. You can fill in the gaps with, rain on a cold day, rain on a warm day, cool dry day, warm dry day, etc.
The available grip dictates how much force can be applied. The opposite will never happen. However, using this reverse approach allows us to test the amount of available grip.
This is all professional racers ever do.
They are always testing the limits of the available grip, because that’s the environment where the lowest lap times live. Acting as if a mouse fart could send them off the track and applying enough force to send that water bottle through any window.