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ABS on a curved, icy downhill

An engineer friend of mine lives at the top of a hill that has a curve in it. If the hill is icy, he believes it would be best to put the autotransmission in Neutral, foot off the gas, and use the antilock brakes to control speed and steer. I think he should put in LOW with foot off gas and use the brakes. Have you run into these conditions? What do you think?

I am with you,has your engineer friend explained how he came up with his technique?

I don’t know what you mean “use the antilock brakes to control and steer” does he plan on braking so hard on a low traction surface that the antilock feature of the brakes must activate to prevent wheel lockup?

…does he plan on braking so hard on a low traction surface that the antilock feature of the brakes must activate to prevent wheel lockup?

Yes, that is the idea. I should have stated things more clearly

Why doesn’t he just go slower,not brake so hard,not activate the ABS? Do you think he is misinformed as to what advantage ABS provides? You don’t want to intentionally put yourself in a position that the ABS must activate.

The brakes act on all four wheels. The transmission only works on two. Which do you think would offer the most control. In any case you want to proceed slowly, if at all. ABS should not change matters, but it may add a level of control that non-ABS systems would not have without it.

In any case, chains or Winter tyres would be a great idea.

Most important of all, is common sense and knowing when to give it up and stay home.

Descending a hill in neutral is not very wise. I’d say shift to low AND use the ABS for control. If the car is going slowly enough the ABS will probably not be activated.

I drive one mile downhill from my house to the first stop sign. The road has an S-turn halfway down the hill, and is often snow/ice-covered.

I would never even think of shifting to neutral to descend this hill. Second gear (automatic transmission) is usually sufficient, but occasionally I have used first. The ABS seldom kicks in, because the car is not going too fast for conditions.

I believe the engineer and Mr. Meehan are ABSOLUTELY right. Anyone else that says differently is absolutely WRONG. That’s my story and…

A free wheeling front wheel retains more steering traction than a wheel being braked or accelerated. Engine/drive train braking can defeat the concept of abs on glare ice and sometimes wet snow that clogs the deepest of treads. I live on a mountain road and have to deal with ice on hills 4 to 5 months out of the year, daily. In addition we have raced on lake ice in the old days.

Drive train drag is not usually a problem in snow…but glare ice is another matter. We consistently depress the clutch to free wheel with a standard when engine braking is more severe than with an automatic which you can often get away with leaving it in gear. Any doubt, slip it into neutral and use the ABS. Appropriate tires is of maximum importance as is prudent speed.

One reason my old front drive 2 stroke SAAB was an effective ice racer was that it had a free wheeling devise (to keep engine from excessive wear, as only lube was from the gas/oil mixture) that would allow you to take corners faster with better control w/o drive train drag as you lifted your foot off the gas.

Lots of momentum is your friend going up an icy hill, it is your enemy going down.

I’m afraid that low gear is the wrong answer. The engine braking may be too severe, causing a loss of control. In addition, the regular brakes have ABS functionality and the engine braking doesn’t. An icy curve is exactly when you need ABS!

However, neutral isn’t really the best idea unless for some reason the engine braking in drive is causing a problem, which I don’t think is likely.

If he has front wheel drive he SHOULD NOT PUT IT IN LOW. 100% loss of control could result. His idea is better. I have run into those conditions. Rear wheel drive may be downshifted. If he is using 4WD, he can just leave it in OD.

“However, neutral isn’t really the best idea unless for some reason the engine braking in drive is causing a problem, which I don’t think is likely.”

I believe that when in doubt, neutral IS the best idea. Look at how abs works. The braking pulse is alternated with a release to allow the wheel to free wheel and regain steering traction. ANY engine braking puts that process at risk.
The engineer is still right.