Is there a problem with anti-lock braking the auto industry isn’t telling us about? Well, the answer is it depends and yes.
The it depends part of the answer is linked to the type of vehicle you drive, front-drive versus rear-drive, while the second part comes out of the first.
The history
A few years back – when we were driving a front-drive minivan – we were headed home following a particularly nasty three-hour drive (that normally took 10 minutes) – when we came up to the front of our apartment complex.
As the complex was off to the right, I turned the wheel to the right and tapped the brakes. Well, I guess I tapped them a little too hard because two things happened:
- The vehicle continued straight ahead, right toward the complex sign
- The ABS did absolutely nothing
It took an old reminder my driving teacher gave me about a thousand years ago to end up in stopping the car short of wasting the building sign and front end of my van and it was simply to get my foot off the brakes and gas and let the vehicle slow itself.
Fortunately, there was enough room for the wheels to grab and quickly swing the car to the right (I had forgotten I had them cranked hard over).
The ABS piece troubled me as I had a $16,000 van, ABS and traction control and nothing worked.
The situation
The road was a sheet of icy slush when I cranked the wheels over to the right and the ABS came on. The traction control just tried to find the best traction for the driving axle (front) and all of that meant I had a vehicle that merrily slid in one direction (understeer), wouldn’t turn until I lost enough speed for the wheels to bite again.
When they did bite, I suddenly remembered they were cut over hard to the right and I was a bit surprised. And, the traction control was practically useless (it just made the front end shudder).
This is a problem inherent with front-drive vehicles. Because the weight distribution is roughly 70-30 over the driving wheels, it means that the vehicle will tend to continue straight in the direction of travel.
On a slippery road, it gets interesting because you can’t steer out of the way (it’s all the pure physics of inertia).
ABS issues
Once you regain control, if you are on a decreasing radius curve, such as an off-ramp, an interesting phenomenon happens called trailing throttle oversteer. It’s simply a function of the type of drive and road conditions. It simply means that once your vehicle regains traction the inner right wheel (usually the traction-bearer). This makes the wheel act as a pivot point and the rear end of the vehicle tries to swap ends with the front.
These phenomena have been known about for years and point out why front-drive is used. PR specialists would have you believe it was for handling, but the real reason is for packaging, as it allows you to put more people inside a vehicle whose outward dimension have shrunk.
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