To Engine Brake or Not To Engine Brake

[Ken Gilbert]

The pressure on the disks is even, but the front has more stopping force
because of the weight shift. This happens with engine braking too.

a) the pressure on the disks is NOT even.. that's why there a
proportioning valve in the hydraulic system.

b) the brake torque produced by a given pressure is NOT even... larger
radius brakes in front lead to more brake torque for a given line
pressure.

c) with less traction available, less weight transfer will take place.

hth
ken

 

[Dominic Richens]

The Forester manual suggested using engine brake more often.

<cynic>
....to the betterment of Subaru mechanics everywhere
</cynic>

 

[Herwig Haentjens]

In some regions you MUST use engine brake (the Alps in Austria and
Switserland): if you drive down from a "col" (San Gottardo, Simplonpass,
....) without engin brake your brakes are overheated and you will have almost
no braking power left when you arrive in the valley (if you will arrive
there!). It is also clearly indicated by roadside panels.

 

[SkaredShtles]

Downshifting to put the car into the best gear after braking is
a better reason.

If you can match your engine speed to the transmission speed you're
basically doing the same thing. I think that what you are talking about is
a PART of engine braking.

-S.S.-

 

[Dave Null Sr.]

If you can match your engine speed to the transmission speed you're
basically doing the same thing. I think that what you are talking about
is a PART of engine braking.

No, I'm talking about the need to downshift at all.

Proper habit is to make sure you always have engine revs in a usable
powerband: ie: not 700 rpm at 20km/h in fifth (or whatever that
works out on your car.) so you can (on the commute road) escape a difficult
situation under power, or (on a windy road) accelerate away at
a satisfying rate.

I should also point out an assumption that you never brake with the
clutch in in normal circumstances. The only exception is in extremely
slippery conditions where you want full control from the brakes without
worrying about the fronts locking up (FWD or auto AWD) and causing lack
of braking or stalling the engine.

Downshifting to slow down the car to 'save' the brakes is not a rational
thought with today's braking systems. Nevermind that I do it
at every stop.

 

[SkaredShtles]

On Sun, 08 Feb 2004 17:21:50 GMT, SkaredShtles
<(e-mail address removed)> wrote in

Downshifting to slow down the car to 'save' the brakes is not a
rational thought with today's braking systems. Nevermind that I do it
at every stop.

Ahhh... but I live near and drive often in the mountains. I will agree
that "speed management" is the goal that I'm working towards. Maybe I
don't do any "engine braking" per se at all...... I just use the
appropriate gear to manage my speed up & down steep slopes.

-S.S.-

 

[Jerry and Bea]

It doesn't. If the engine & transmission speeds are matched before
releasing the gas pedal there will be virtually NO wear on the clutch.
Engine braking is a great way to prolong brake life. Especially if you
frequent the mountains.

-S.S.-

So why would you want to prolong your brake life at the expense of your
engine? Brake pads are cheap compared to internal engine parts. I'm just
trying to point out the other side of this often discussed, yet never really
solved argument. There are times when you should use the brakes and times
when using the engine is the best, most of the time the best is a little of
both. I should point out that I live in a mountainous area and you can
always tell a flatlander has been around when you smell those brakes
cooking!

 

[Greg Reed]

In my own opinion, i live in a town where it is either rainy, or
snowy / icy, so engine breaking has been very useful. for instance, i
was driving home last night, and rarely had to use the brake pedal. i
control my speed mostly with the accelerator and gear im in. there is
a stretch at the end of the highway where you go from 55 to 40 to 35,
over a bridge, and back to 40, and it just came natural to use engine
braking and gear shifting to get through that area than use the
brakes going through that area and over the bridge twice a day.. i
have always been told that there is no problem 'letting the engine do
some work'..

just my opinion
JB

I, too, use quite a bit of engine braking. But there is one thing that I
haven't seen mentioned that I think it worth pointing out: In wintertime,
you can find yourself in a situation where your engine braking is too much
for the available grip. I'll grant that it doesn't happen often, but it can
happen. In such a situation, you won't have anything "automatic" like ABS
to prevent the car from going into an uncontrollable 4-wheel slide (for AWD
vehicles). The appropriate response when you sense a loss of grip under
engine braking is either apply more throttle or depress the clutch. If
you're at a relatively high speed and in a higher gear, you can probably get
away with the former option. At low speeds and in a low gear you're
probably best off depressing the clutch and switching to brakes, as it would
be easy to apply *too much* throttle and make the situation worse rather
than better.

- Greg Reed

--
1976 Cadillac Fleetwood 75 9-Pass sedan
(FS: http://www.dataspire.com/caddy)
1989 Audi 200 Turbo Quattro 5-Speed sedan
2000 Oldsmobile Intrigue
2001 Chevy Astro AWD (wife's)
2005 Subaru Legacy GT Wagon (when available in U.S.)

 

[knowone]

If you operate the clutch properly, there is no harm. My daughter is
driving my 91 Honda accord and it has 175,000 miles on the original
clutch. Engine breaking also got me over 100,000 miles on the original
set of brakes.
I hope this helps

 

[Verbs Under My Gel]

I don't know if you guys out there use engine brake so often or not. I found
it very useful in Winter.

However, I'm afraid doing so may damage the clutch.

If you rev-match on the downshifts, you won't cause any undue wear to
the clutch disk.

 

[Ken Gilbert]

Ahhh... but I live near and drive often in the mountains. I will agree
that "speed management" is the goal that I'm working towards. Maybe I
don't do any "engine braking" per se at all...... I just use the
appropriate gear to manage my speed up & down steep slopes.

-S.S.-

generally a good rule of thumb is to be going downhill in the same
gear as you would use when you go up the same hill.

ken

 

[Alpha Male]

Arent brakes cheaper than clutches? Why would you want to destroy your
clutch? Stop doing that my man, brakes are cheaper.

What??? Do you know ANYTHING at all? Downshifting (enigne braking) is one
of the biggest benefits of a manual transmission. Saves brake life,
provides better winter traction when slowing down (no chance to lock the
brakes). The clutch can totally handle this, that's what it is designed
for!

One of the dumbest things I've ever seen is people who have manual
transmission and use their brakes to slow completely down. If you have any
skill at all, you can slow almost to a stop using the transmission and just
use the brakes to totally stop the vehicle.

Chris

 

[Alpha Male]

Not ture. If you downgear on slippery conditions and there is not enough
available grip, it's not like the tires will lock up, they'll just slide a
bit. Unless you are a very unexperienced driver, you'll be able to keep the
car straigh until the tires catch up to the speed of the car, or the car
slows down enough.

Some people may argue that engine braking eliminates ABS, but that's only
because you don't need ABS for enigne braking. ABS is only for COMPLETE
MORONS who don't know how to drive and stamp on the brakes, locking all four
wheels. I've disabled the ABS on my car because it's absolutely stupid.

ABS = Training Wheels for Adults.

Chris

 

[David]

It's not a matter of clutch disc wear.

When you use engine braking, you're applying force in the opposite direction,
which is ordinarily OK. I use engine braking too. But if you do it excessively,
you can make your clutch vibrate & chatter. I think the problem is wear in the
pilot bearing.

 

[David]

On Sat, 07 Feb 2004 17:50:43 GMT, (e-mail address removed) (J999w) wrote in
Engine braking is completely unnecesary in modern cars.

Not true. I've smoked the brakes in a couple of medern cars in spirited
driving, both automatics. Also, I've seen several cars smoking at the
bottom of a popular shortcut heading west from Yosemite. I even saw
a full-sized Bronco smoking at the bottom of that hill, and I always expect
big trucks to have excess braking capacity for towing. It's that only hill I
can think of where I'll engine brake even with an automatic. My first time
down, I was driving an automatic, and had almost no brakes left at the bottom,
Smoking from at least 3 of 4 corners. The braking didn't come back properly
as things cooled down. Pads glazed, calipers leaking, rear brake shoes cracked.
I'm happy to have a stick shift now, as I don't think engine braking with an
automatic is such a good idea (IIRC I needed a trans fluid change after one
descent).

 

[Rob Duncan]

Actually, you can downshift to engine brake - using the clutch - without
overtaxing it. Just match engine revs before releasing the clutch, so that
the engine is already going the correct speed for your new gear and road
speed. Wait until the clutch is fully released before lifting the throttle
to provide engine braking and spare your brakes. (Though I'm not sure that
sparing the brakes is a good reason to employ engine braking. I prefer to
use a lower gear in traffic because it gives me better control over my speed
with only the throttle. The trade-off, of course, is increased fuel
consumption. But with gasoline cheaper than bottled water here in the
'States...)

What destroys a clutch is excessive and prolonged speed differential between
the two plates. Raising engine RPM with the throttle to what it will be
with the clutch released *then* releasing the clutch doesn't cause any
additional wear. OTOH, shifting into a lower gear then letting the clutch
force the engine up to the appropriate revs for the new gear will definitely
increase clutch wear. As long as the speed differential between the engine
and the tranny is minimal, so will be the wear on the clutch.

Actually, one should *always* rev match when downshifting, if only to make
your driving smoother and thereby reduce neck strain in your passengers .
And I always try to double-clutch my downshifts to save the synchros as
well, but that's probably a bit over-the-top in a modern manual-transmission
car. Old habits, you know. I never got very good at using the heel and toe
of my right foot to operate the gas and brake pedals at once, so I don't
bother with the double-clutching if I'm on the brakes while downshifting.
The only time I do the heel-and-toe thing is accelerating from a stop on an
incline when some dork pulls right up on my bumper. Though I understand I
won't have to do that with my new Subie, since they all have that neat "hill
holder" feature.

And the only time I've ever shifted sans clutch is on a motorcycle. I've
never been brave enough to try it in a car. I can match revs pretty well,
but I don't get it perfect every time -- which is what would be required to
shift without the clutch. I suppose if I was in a pinch -- like with a
broken clutch cable -- I might give it a whirl. But I've fortunately never
been in such a pinch.

- Greg Reed

My father taught me how to shift in an old International Pickup. No clutch.
Try being a 4/ 1/2 ft tall 14 yr old learning how to drive in that thing.
LOL GRIND!


Rob

 

[Rob Duncan]

Not true. I've smoked the brakes in a couple of medern cars in spirited
driving, both automatics. Also, I've seen several cars smoking at the
bottom of a popular shortcut heading west from Yosemite. I even saw
a full-sized Bronco smoking at the bottom of that hill, and I always expect
big trucks to have excess braking capacity for towing. It's that only hill I
can think of where I'll engine brake even with an automatic. My first time
down, I was driving an automatic, and had almost no brakes left at the bottom,
Smoking from at least 3 of 4 corners. The braking didn't come back properly
as things cooled down. Pads glazed, calipers leaking, rear brake shoes cracked.
I'm happy to have a stick shift now, as I don't think engine braking with an
automatic is such a good idea (IIRC I needed a trans fluid change after one
descent).

Sounds like your car needed some work to begin with.


Rob

 

[David]

Sounds like your car needed some work to begin with.

Nope. And I only smoked brakes there once, but I've seen others do it several
times. In fact when we see cars at the bottom, it's nearly even odds their
brakes will be smoking.

 

[Mike Minerva]

Dave Null Sr seems to be the only one who understands the true benefit of
engine braking, i.e. to be in the proper gear to accelerate when the need
for stopping ends.

 

[Alex]

solved argument. There are times when you should use the brakes and times

when using the engine is the best, most of the time the best is a little of
both. I should point out that I live in a mountainous area and you can
always tell a flatlander has been around when you smell those brakes
cooking!

How about using both the breaks and the engine? Not as much wear on
the breaks and you get in a habit of downshifting, which can help a
lot in difficult road conditions, such as in winter when it's
slippery. If you don't downshift as a rule, who's to guarantee that
you're gonna do it right when you really need it?