Reader Question: Coasting?

Here’s the latest reader question, along with my reply!

Nasir asks: Hope you are doing well. Currently am doing a bit of traveling around the UK, and in the Lake District in Cumbria, and had a driving related question – couldn’t think of a better person to ask. Around here, there area a lot of bendy and hilly roads, some with steep gradients. One thing I see before the slopes is a sign saying “high gradient, keep in low gear” (or something of the sort). I however tend to hold the brake, and when/if it starts to stall just push the clutch, or if long enough downhill put it into neutral and control speed via the brake. That said, one thing I remember always being told by my driving instructor when giving the UK driving test is that this is “illegal” as it is “unsafe.” I however find that it tends to put less strain on the drivetrain instead of holding it in gear. Fine, granted I probably don’t have the best driving habits (as I learnt, let’s say unorthodox way before I moved to the UK)…. but I can’t think of how this is actually “unsafe.” Maybe, back in the day when brakes weren’t that good, and engine braking was needed; fine, but with modern cars with power brakes well they will hold on anything. Or if you hold the clutch too long it can wear, but why not just put it into neutral?

What are your thoughts on this?

My reply: “Coasting” – disengaging the drivetrain by placing an automatic in neutral or holding the clutch in while the vehicle’s rolling – is supposed to be dangerous because of the increased chance of a vehicle overspeeding and the driver losing control.

Personally, I don’t see it – unless (as you’ve already guessed) the car has really weak brakes and they get too hot and fade. It’s possible, certainly – but probably not unless the car is really old (cars made before the ’90s sometimes did have weak – or rather – marginal – brakes) and you’re descending a steep grade.

In my experience – extensive – you have to be really working any late-model car to get the brakes hot enough for fade to become a issue. Mere coasting probably won’t do it. I’ve only succeeded in doing it when I’m running the car as one would on a race track; decelerating hard from high speed, accelerating to high speed – repeat. Many times. Do that – and, yeah, the brakes will get hot and if they’re not meant for that sort of abuse, they’ll get too hot and then you may have an issue…

But otherwise? I doubt it.

Interestingly, several new cars have a “coasting” (or “sail”) feature that works on the same general principle. The car’s engine is automatically turned off during light load conditions to save microcosmic quantities of fuel.

In the situation you’re describing, you may save a little gas – at the cost of more rapid brake wear, from having to ride the brakes to keep the vehicle’s speed in check while going downhill. Brake pads, calipers and rotors cost more than a little bit of gas, so . . .

My personal practice is to downshift (if the car has a manual transmission) to whatever gear is needed to maintain my speed on a descent without having to ride the brakes; you can do the same thing with most late-model automatics by disengaging the OD or (if it has manual gear selection capability) notch down one or two gears. Of course, if it’s automatic, it ought to do all that . . . automatically!

But, some automatics aren’t programmed that well; and some are programmed to upshift (for economy) and that can be unsettling when descending a steep grade. In that case, manually shift the transmission into a lower range for the engine braking effect.

. . .

Got a question about cars – or anything else? Click on the “ask Eric” link and send ’em in!

If you like what you’ve found here please consider supporting EPautos.