Not only that but staying in gear when going down hills or slowing down will reduce the wear on your breaks by using the inertia of the engine to slow the car instead of break pad friction/heat.
You maintain better control of the vehicle if you leave the clutch engaged and engine brake instead of slowing down with it disengaged and using the actual brakes. It may not seem that way to inexperienced manual drivers, but once you've driven a manual in traffic a few times you learn that engine braking is safer and more precise.
Also, on a large, heavy vehicle with a manual transmission, you can get in trouble with misjudging braking time/distance if you only rely on the brakes to slow down and stop. When I have a full load in my pickup (1982 C10) I have no choice but to engine brake as the wheel brakes lose more stopping distance the heavier the load, not to mention it keeps them from overheating and failing early over time.
Cars are designed so that you stop the car by pressing the brake pedal, so that is generally the better way to do it.
* 4-wheel braking, even if it is a 2wd car.
* ABS/Traction control systems are designed around brakes, not engine braking.
* Regenerative braking (if equipped) uses the brake pedal
* There is a smooth application of braking power from 80mph to 0mph. Engine braking is indexed (I can only choose which gear), and cannot bring the car to a complete stop.
* The limiting factor with brakes is traction, which isn't improved by using engine braking.
* Using the brake pedal is a single action. Engine braking involves at least 3 (clutch in, shift, clutch out).
* Brakes are cheaper to replace than clutch/transmission.
* Engine braking alone does not activate brake lights.
The only exception is when there is a danger that the brakes will overheat: descending a large hill or hauling a heavy load. The default instinct should be the brake pedal alone.
> Cars are designed so that you stop the car by pressing the brake pedal, so that is generally the better way to do it.
I wasn't speaking of coming to a complete stop, only of slowing down with the flow of traffic. I should have worded it better, I'm sorry.
> Using the brake pedal is a single action. Engine braking involves at least 3 (clutch in, shift, clutch out).
But if you're already downshifting while slowing down, which you should be, it's actually not extra effort. It's completely natural.
> Brakes are cheaper to replace than clutch/transmission.
That entirely depends on the vehicle and the type of clutch. In my extensive experience (I repair cars on the side, and have done so my entire adult life) the parts themselves often cost about the same. For example, when restoring my Bronco II I bought a clutch kit for $150 and a full set of front brake rotors, pads, and new calipers for about $200.
On my Crown Victoria, which was formerly a police vehicle and therefore has the upgraded heavy duty disc brakes on all four wheels, a shop quoted me $700 for a brake job. The parts alone were $350 through them. Of course I saved a ton by doing it myself, but most people can't or won't do that. The labor for a clutch swap versus a brake job is, again, dependent on the complexity of the vehicle. Most manuals still in use in the US are older model cars, with relatively easy to replace clutch parts.
> The only exception is when...hauling a heavy load.
Which I specifically spoke of. :-)
> The default instinct should be the brake pedal alone.
In an automatic, yes. In a manual, only when needing to stop suddenly or when you've downshifted to 2nd or 1st and you're stopping altogether.
This makes particular sense for a pickup. When unloaded the truck's weight balance significantly skewed toward the front, allowing for less traction in the back, and so you need to rely on the front wheels more for braking. When you're loaded, that's sitting more-or-less over the rear axle, increasing traction there. So you can afford to rely more on the rear (driven) wheels with engine braking in addition to the conventional brake balance that's biased to the front.
I tend to engine brake except in circumstances where I actually need more braking power.
Especially with hilly driving, it gives you a lot more control when slowing down, and you can accelerate straight away since your foot is still on the accelerator pedal.
There's nothing worse than being stuck behind a driver (usually a tourist) in a hilly area who is riding the brakes all the way down.
In my head, using the engine/transmission to "brake" when in gear going down hills or slowing down seems like a bad idea. Something is getting stressed in order to slow the car down.
Having to replace my brakes makes sense, they get worn out, and its relatively inexpensive (especially if I do it myself). I have always been wary of staying in gear to brake. And, as it so happens, my manual has 130k miles on it, stock engine, transmission, and clutch. Never had any problems.
I would love to understand the science behind why using the engine/transmission/clutch to brake is better for the car than just using the brakes.
Your engine is designed to withstand fuel-air explosions. When engine braking, all it does is compress and expand air, at much lower pressures, so revolutions during engine braking are easier on your car than those during regular driving.
Clutches get less wear during engine braking because it doesn't slip. When you disengage and reengage the clutch because you're using the regular brakes to slow down, the clutch slips and damages itself.
In the end, the reason for engine braking isn't to reduce the cost of brakes--it's a safety measure that keeps the brakes cool for emergencies & miscalculations, since overheated brakes don't work.
> Clutches get less wear during engine braking because it doesn't slip. When you disengage and reengage the clutch because
> you're using the regular brakes to slow down, the clutch slips and damages itself.
And when you have to change down, while engine braking? (I have an odd learning style. Please don't mistake this for "You're wrong because..." It's a case of "I don't understand why, so...")
A friend once told me that the UK required you to half-engage the clutch while using the brakes and the engine together. I've also read something to the effect of modern brakes are much more efficient so (at least one) UK "advanced driving school" teaches that it doesn't really matter.
I have an older car (1998 Mazda 626 wagon). It's a manual, and when I drive downhill I put it into third and let it coast, braking to reduce speed. Should I be putting it into second, and letting it run up to 3500-4000 revs? Should I leave it in third, and use the brakes? Does it consume more fuel to do this, in a car of that era?
I've often meant to ask my local mechanic about this, but never think about it when I'm there.
Drive with clutch disengaged. Use clutch only while you quickly shift into an appropriate gear. The longest I use clutch is when I am starting of from a stop in first gear. Once I have momentum, dip clutch fully and shift and release clutch as soon as gear us shifted. When clutch is half pressed, clutch plate gets highest wearing as plates are half pressed against each other, not enough friction is there to stop clutch disc slipping (as it is while clutch is not engaged) against each other thus causing wear. When clutch is fully pressed, the clutch plates are seperated so they dont rub against each other and wear.
The way I shift is as I approach a downhill I keep driving it in gear rather than coast. If its steep downhill, you can brake ahead to lower your speed to something you are comfortable at. Shift down to the gear for that speed and then back off the gas if you need engine braking. You can use brake in combination with engine braking gear if you needs to slow down more than using engine braking alone. I shift down when speed gets lower than in current gear.
The Car Talk guys addressed this and agreed with you. It's better to use the brakes to slow down since they're ablative and designed to be replaced with wear. Causing the engine to do extra revolutions means extra wear on something that's quite difficult to replace/repair...
That said, I drive a manual and use the engine for braking...
Growing up in the mountains, in Colorado, it was drilled incessantly into me how important it was to use engine/transmission braking on long hills, etc.
I know it, I understand it ... and it always irked me.
I never liked the idea that I would save wear and tear on a consumable that is meant to be regularly worn and repaired and instead transfer that wear and tear to an integral part of the car that is non-trivial to replace or repair.
I would think very carefully about this if I were towing a boat or a horse trailer, but in a normal car it just seems backwards.
It's not about wear and tear. Brakes heat up when they're used, and descending an entire mountain on the brakes is likely to overheat them to the point where you have no braking power left at all. Not a good situation to be in on a steep slope. Using engine braking to keep your speed under control prevents this.
Engine braking imposes negligible wear and tear on the engine. Instead of fuel-air explosions driving the pistons up and down, the pistons inefficiently compress and expand air at ambient temperature and pressure. Sure, extended use might take 100 miles of life off a 300,000 mile part, but are you really going to worry about that?
I believe the reasoning here is that braking all the way down a steep grade can cause your brakes to overheat and become temporarily inoperable. I don't know whether this is a real effect or not, but I have heard it given as a justification for engine-braking.
It's definitely a real thing. It's usually referred to as "brake fade" in car enthusiast communities. It’s usually more of an issue when racing, but it can happen if you have to do many hard stops during regular driving as well. I think it has to do with the pads releasing a gas when they get hot which creates a thin layer of “air” between the pad and the rotor.
It's the reason that sports cars generally come with bigger brakes. Sure, a Toyota Corolla might be able to stop in a similar distance, but things change when you have to do it 5 times in a row.
Oh yeah its real. Back 20 years ago I came down from Guenella Pass to Georgetown in Colorado and just about lost my brakes on those switchbacks just above Georgetown. One of the scariest situations I've been in.
This happened to a friend of mine driving through the rocky mountains in Canada; brake system overheated and he had no breaking ability until it cooled down.
unkeljoe: "braking all the way down a steep grade can cause your brakes to overheat and become temporarily inoperable. "
That condition is known as brake fade/fading and occurs mostly with drum brakes and can occur on bicycles, motorbikes and automobiles.
Braking heats the brake drums, which then expand. The drum may expand in diameter to the extent that the brake pads no longer contact the drum sufficiently enough to slow the vehicle. Your brakes "fade" away.
Many vehicles have disc brakes in front and drums on the rear, an arrangement usually sufficient even in hilly country. Of course when pulling a boat or trailer having all disk brakes would be a safer bet.
Brake drum fade is by far the most common manifestation, but there are other types of "fade", e.g., brake fluid can get heated up enought to boil and reduce braking system pressure, brake pads can "slip" more at extremely high temperatures:
Last ditch efforts: shift into a lower gear, use any emergency brake (which is mechanical and bypasses the braking fluid system and so won't fade due to boiling fluid), and finally, use the inside of a hill/mountain as a giant brake pad by sliding your car's body into it as gently(!) as possible.
Finally I feel compelled to warn anyone who ever pulls a trailer, boat or RV about a potentially fatal phenomenon they may encounter on even gently sloped roads: undamped driven harmonic oscillation between towed and towing vehicle. My first experience:
VW Beetle towing a U-Haul trailer on a Pennsylvania turnpike mountainside. Traffic moderate in both directions.
On a long downhill segment the trailer hitch began to move to-and-fro left and right, gently at first but, as I attempted to correct with steering, rapidly growing in amplitude. My steering reaction time and corrections were unfortunately timed precisely so as to _increase_ the amplitude of the oscillation. In a flash the rear end of the Beetle was hopping right and left! Insight - I need to dampen the oscillation. I gripped the steering wheel, braced both forearms against my legs and reduced all steering corrections to a minimum (I just kept the car on the road and in the proper lane). The car's front end skidded left and right as I kept the wheels as straight forward as possible. Then I slowly applied the brakes. This brought the oscillations under control and the speed down. I continued the trip at a much slower speed despite the honking of frustrated drivers behind me.
That first experience, enhanced by both impending ignominious death on a mountainside and the sudden realization of the utility of my mathematical physics class* [1], was exhilarating.
In the years since I have myself seen this occur several more times, which makes me think it must be a not-uncommon event that requires some warning.
It once again occurred on IH 10 between Houston and New Orleans, one of the flattest pieces of land in the USA. A heavy-duty six-wheeler pickup was hauling a trailer full of goods on an extremely gentle slope at near 70-mph when his trailer hitch began to oscillate left and right. I had been following and observing his truck and noticed that the system seemed to be periodically oscillating, so I stayed well back and did not attempt to pass even on a four-lane highway. Finally things took a turn for the worse and, within 6 seconds of back-and-forth oscillation and attempts at correction, both truck and trailer were driven off the road into the grassy median. Luckily the median was wide flat grass and no harm occurred to driver, truck or trailer. I stopped and crossed the road as the driver took off his cowboy hat, waved it at his truck and trailer as if dismissing an unruly horse, bent his back, and put his hands on his knees in amazement.
I spoke to him awhile, reassured him and gave as best an explanation to him of what I saw and what he might do to prevent further mishaps. He was quite out of sorts and I'm not certain he was fully able to absorb the lesson. He was definitely astonished to find himself on the median with his truck and trailer turned around 270 degrees from the direction he intended.
Had this happened on a strip of highway without such a wide median the truck would have driven at ~60 mph into ongoing traffic at 70 mph. Had this happened on a hillside, I would estimate a 50% chance of both vehicle and trailer plummeting downhill. For these and other reasons, I think this phenomenon must kill more than a few people each year.
Very similar but there was an additional degree-of-freedom, the driver's steering (and braking), which can either improve or worsen the situation. Initially I tried to countersteer to correct the oscillation, but I was too slow - the oscillation amplitude increased! Changing tactics to damping the oscillation by keeping the wheels as straight ahead as possible (and slowing) did the trick or I likely wouldn't be posting this!
I needed to get to the Northeast for a summer job. One of my professors had a Beetle and a locked U-Haul that she wanted moved to Boston. Now that I look back I probably should have asked to see the contents of the trailer!8-))
It was a fun trip with only a minute or so of harrowing possible death-down-the-mountainside. I'd recommend it to anyone!
The theory is if you go down a long mountain the brakes will be very hot when you are getting towards the bottom which means the performance is not as great. So if you then suddenly need the full power of the brakes it is not available anymore.
Also if the mountain is tall enough the brakes might not make it all the way down which has happened a few times in Norway with catastrophic results for large vehicles like busses.
I just listened to Click and Clack a couple weeks ago, and a guy called in asking why his brakes caught on fire after he went down a long hill.
Suffice to say that they do not recommend against engine braking--quite the contrary. Think about it: the engine is already spinning, so spinning it at a higher RPM for a few tens of seconds does no more wear than accelerating.
The issue is not brake wear--the issue is brake fade, and potentially boiling your brake fluid!
When you're going down a long hill, downshift and save your brakes! It could save your life!
>Something is getting stressed in order to slow the car down.
The exact same components that are stressed in order to speed your car up.
Since your engine doesn't have combustion raising cylinder pressures, the total power 'absorption?' under engine braking is necessarily less than the full power output of the engine which the drive train was designed to handle.
The exception is if you have rear wheel drive and enough weight transfer to the front to get wheel hop. But, afaik, this is a problem unique to motorcycles.
When breaking with engine, the kinetic energy of movement is converted to heat not via friction (like breaks do) but via compressing air in cylinders which does not cause extra wear on anything.
>> Just what the previous commentor said: saves on wear and tear on the brake pads.
When I was learning how to drive a manual, my Dad was a huge fan of them and all of our family cars were manual. I was taught that it makes a huge difference when you're driving in the mountains to use engine braking instead of your brakes. He also explained the difference in braking in traffic and using engine braking to do so and how it supposedly saves on gas as well - something about idling the engine versus continuing to have the engine running?
I'd be interested to hear from people who regularly drive in the mountains and the advantages/disadvantages of engine braking versus using your brakes and if that was some myth or actually real.
The point about gas is certainly true, thought I can't speak to the rest as much.
While you're accelerating, you're giving the engine gas to keep it moving and prevent a stall. While braking you aren't accelerating, but you still need the engine to keep going at speed.
If you depress the clutch, it disconnects the engine from the wheels. The engine will then get a trickle of gas (even if you don't accelerate) to keep it moving while the car breaks.
If you don't depress the clutch, the engine stays in connection with the wheels. Their motion drives the engine - the reverse of normal - keeping it moving without burning any gasoline at all.
It's not generally a big difference, but if you're in the hills of Colorado you might care more.
