Well, g

Tony Quiroga in Car and Driver:

A Michelin engineer who tests driver behavior once told me, “Most people, when faced with cornering beyond 0.4 g or hitting a tree, choose the tree.”

Well, I guess a tire guy would know, right?

Judging by typical cornering speeds on public roads, and my mother-in-law’s reaction to me pressing way beyond 0.4 g, I’d say he’s probably right. Usually, the g-force, or gravitational force — by definition, gravity is 1.0 g — is felt in the downward direction as one’s weight; it’s what keeps your feet in contact with the ground. A lateral g-force such as what one experiences in a car that is cornering is also measured in the same units (g). Most cars today can corner at more than 0.8 g; 0.4 g translates to about 45 mph on a freeway entrance ramp marked at 35 mph.

Not having an accelerometer handy — geez, another argument for an iPhone — I can’t verify this personally, but somehow that seems awfully modest. Or maybe I’m driving harder than I think I am. The ramp from I-44 eastbound to I-35 southbound, which I use five days a week, sometimes six, is about a 75-degree curve that I routinely take at 60 mph unless it’s wet or the 6:30ish traffic doesn’t permit. (I’m going from a road where the speed limit is 60 to a road where the speed limit is, um, 60, so 60 seems like the most logical speed.) In fact, I consider this a test of car and/or tires: if there’s any squeal, it’s a fail. Hardly anyone else pulls this sort of stunt, which makes me wonder if I’m pushing too hard.





7 comments

  1. Jennifer »

    2 October 2009 · 4:23 pm

    Not at all. It’s just that most people scare far too easily. That’s why they drive big cars with squishy suspensions that make them feel safe.

  2. CGHill »

    2 October 2009 · 4:24 pm

    Or big trucks that don’t have squishy suspensions but that have centers of gravity entirely too far above the pavement to suit me. :)

  3. McGehee »

    2 October 2009 · 5:22 pm

    Hey!

  4. CGHill »

    2 October 2009 · 6:04 pm

    To each his zone, say I.

  5. Jeffro »

    2 October 2009 · 9:26 pm

    I’ve kinda sorta discovered the limits (perhaps just the limits I’m willing to push) of the truck I drive – there are a few gratifying moments on certain ramps where I often leave a tailgating car behind. Usually a 45mph curve taken at 60 or so – the slower marked curves usually “mean it” when it comes to Class 8 vehicles.

    .4g in the truck? Probably not.

    The ‘Vette I had – in it’s day – handled better than it’s contemporaries. The frame flexed and the suspension was hard, so pictures of them at speed in gymkhanas usually had them cornering on three wheels. So, compared to more modern cars, it’s strength was merging.

  6. CGHill »

    2 October 2009 · 9:51 pm

    Just for the sheer hell of it, I tackled that curve today at 66 mph.

    Still had grip, and no squealing, but damn near scraped off the door handles.

  7. unimpressed »

    2 October 2009 · 10:55 pm

    Try that on TWO wheels, Charles. It’s a rush. I used to routinely take cloverleafs at 65 and 70 and never felt I was even close to pushing it.

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