7 ms·

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 i

by po 10y ago

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.

irishcoffee 10y ago
I've always wondered about this. 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.
- JoeAltmaier 10y ago
  Just what the previous commentor said: saves on wear and tear on the brake pads. As for wear on the engine: the engine is actually designed to mesh with the transmission. Engine braking is not much different than accelerating.
  - at-fates-hands 10y ago
    >> 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.
    - Bartweiss 10y ago
      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.
- aleh 10y ago
  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.
  - CoffeeDregs 10y ago
    I think you're referring to "Jake Braking", which is very noisy and is banned in many towns (in California). https://en.wikipedia.org/wiki/Compression_release_engine_brake https://en.wikipedia.org/wiki/Compression_release_engine_bra...
    - Unklejoe 10y ago
      "Jake Braking" is similar, but pertains more to diesel engines which have a special valve to support this since they work differently. Engine braking on a gasoline engine is actually quieter than normal operation.
    - mmagin 10y ago
      At least the manufacturers of those products assert that correctly installed ones are no louder than the diesel engine in normal operation. http://www.jacobsvehiclesystems.com/about-us/environmental-health-safety/noise-concerns/ http://www.jacobsvehiclesystems.com/about-us/environmental-h...
- CoffeeDregs 10y ago
  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...
  - rsync 10y ago
    I have always thought this. 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.
    - corey_moncure 10y ago
      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.
      - wvenable 10y ago
        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.
      - deleted 10y ago
        [deleted]
      - Unklejoe 10y ago
        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. For most people, it’s not really an issue though.
- hx87 10y ago
  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.
  - dvtv75 10y ago
    > 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.
    - rubberstamp 10y ago
      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.
- Rzah 10y ago
  Your drivetrain is designed to withstand the stress of acceleration, normal engine braking isn't going to register.
- zardo 10y ago
  >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.
morganvachon 10y ago
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.
- CWuestefeld 10y ago
  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.
- crznp 10y ago
  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.
  - 10y ago

by po 10y ago

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.

irishcoffee 10y ago

I've always wondered about this. 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.

JoeAltmaier 10y ago
Just what the previous commentor said: saves on wear and tear on the brake pads. As for wear on the engine: the engine is actually designed to mesh with the transmission. Engine braking is not much different than accelerating.
- at-fates-hands 10y ago
  >> 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.
  - Bartweiss 10y ago
    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.
aleh 10y ago
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.
- CoffeeDregs 10y ago
  I think you're referring to "Jake Braking", which is very noisy and is banned in many towns (in California). https://en.wikipedia.org/wiki/Compression_release_engine_brake https://en.wikipedia.org/wiki/Compression_release_engine_bra...
  - Unklejoe 10y ago
    "Jake Braking" is similar, but pertains more to diesel engines which have a special valve to support this since they work differently. Engine braking on a gasoline engine is actually quieter than normal operation.
  - mmagin 10y ago
    At least the manufacturers of those products assert that correctly installed ones are no louder than the diesel engine in normal operation. http://www.jacobsvehiclesystems.com/about-us/environmental-health-safety/noise-concerns/ http://www.jacobsvehiclesystems.com/about-us/environmental-h...
CoffeeDregs 10y ago
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...
- rsync 10y ago
  I have always thought this. 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.
  - corey_moncure 10y ago
    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.
    - wvenable 10y ago
      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.
    - deleted 10y ago
      [deleted]
    - Unklejoe 10y ago
      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. For most people, it’s not really an issue though.
hx87 10y ago
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.
- dvtv75 10y ago
  > 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.
  - rubberstamp 10y ago
    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.
Rzah 10y ago
Your drivetrain is designed to withstand the stress of acceleration, normal engine braking isn't going to register.
zardo 10y ago
>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.

morganvachon 10y ago

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.

CWuestefeld 10y ago
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.
crznp 10y ago
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.
- 10y ago