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Downshifting on a steep hill

There is a steep hill (45 degree grade) about a tenth of a mile from top to bottom near my home. It has a speed limit of 25mph. Whenever I go down this hill, I shift down into First gear and semi-coast all the way down, doing between 20 and 25mph. I do this because I don’t want to wear out the brakes. Is this correct? If not, why are there signs on steep hills encouraging / requiring truckers to downshift?

how can you semi-coast and be in first gear at the same time?

Keep your car in gear and control your speed with the brakes

Well, sort of. The reason why you downshift is to avoid overheating your brakes, which on a little .10 mile hill isn’t really going to happen. Brake overheating becomes a risk on long steep downgrades where speeds are higher but would require constant brake pressure to limit them. This is especially a problem on deceptively steep grades, which is usually where you see the signs. It’s also a somewhat bigger issue for trucks because obviously they’re heavier, but also airbrake systems can catch on fire if they overheat!

On your little hill, you can probably do it whichever way you like. You might shorten the life of your brakes somewhat by going down the hill in a higher gear, but if your engine is revving to within a 1000 or so RPM of the redline in first it’s not especially good for it, especially if you’re just starting out and the engine’s cold. Second gear might be a good compromise.

I “semi-coast” by putting the car into First and giving light pressure to the throttle. That’s very possible in a four-speed automatic.

GreasyJack said it.

Myself, I would keep the shifter in 1st and (gently) apply the brakes off and on to the bottom. This way you can control the speed and save brake wear. So what if it takes 5 seconds longer?

Generally, the rule is to motor DOWN a hill in the same gear you would go UP it.

A 45 degree hill is almost hill climbing.

For that short of a descent I would use the brakes. They are much cheaper than engines. No way you have a 45 degree angle, BTW, on any public road or street.