Had a discussion (argument) with a colleague this morning on the 'best' technique to use when descending relatively short hills. Not your Alpine pass variety, just a mile or so which proves too steep to keep in check simply by closing the throttle.
I've always favoured braking using a series of relatively forceful (but not sharp) applications of the middle pedal (or the left-hand one for us auto drivers!), whereas my friend advocates steady continuous braking all the way down the hill. I can't really back up my argument with blinding science - it's just a 'gut feel'. What do you think?
I've also found that braking reasonably firmly from the start in normal driving makes it much easier to 'taper off' if coming to halt, avoiding 'dipping' the bonnet - which I find a wee bit irritating when I'm a passenger!
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I also drive an auto. Personally I either hit the "S" (sport) button so that the gearbox changes down into 3rd gear, or if a steeper hill, move the gearstick into 2nd and let the engine do the braking.
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Thanks, DD. I've got mixed feelings regarding 'engine' braking. It's not really the engine, but the gearbox which does the braking - all the heat associated with the vehicle retardation has to go into the transmission fluid, which I can't imagine is a good thing. It's far easier (and cheaper!) to replace brake pads and disks.
Someone once advised me that engine braking dates back to when brakes were woefully inadequate cable- or rod-operated affairs, prone to uneven effort at each wheel. His attitude was to let modern brakes do what they were designed to do.........
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All over France on long autoroute downgrades they have signs in 4 languages saying "use your engine braking".
This is what I was taught many moons ago (army instructor) and with the Jeep's automatic it's easy to knock off the "overdrive" button which does the job even with the caravan in tow.
Whatever you do, heat will be generated. Brakes will only be cooled by airflow (and the fluid not at all) but at least gearbox oil gets some cooling assistance.
Terry
"Just because I don't care doesn't mean I don't understand"
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Some very good points here LHM, Graham Hill (for one) never used engine (or gearbox) braking - not even at Le Mans, especially so perhaps. His reasoning didn't really have much to do with heat dissipation, more the adverse effects of repeated reverse loading on the transmission elements. As you (and G.H.) said, brakes and discs or drums are far easier and cheaper to replace than transmissions.
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In the old days of drum brakes and lesser brake fluid technology it was a good idea to let the drums cool in some airflow by using your technique of braking then releasing. With disk brakes and modern fluid, I can't see it makes much difference. After all, the energy dissipation is the same whatever technique you use unless you accelerate between brake applications.
I'm all for a healthy brake application on slowing from speed; as my dad used to say "The sooner you find out your brakes don't work, the better".
Hawkeye
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Stranger in a strange land
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My habit is to use both engine braking and the brakes ? every little helps. But it is deeply ingrained from being told decades ago that allowing revs to rise with your foot off the throttle was good for the engine in that it draws oil up the cylinders. That may be complete nonsense for all I know, but I think it came originally from a reputable source. Someone here will put me right, I'm sure, and I look forward to it.
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Uss the same gear down a hill as the one you would use to go up it was always what I was taught. Its not true in every case, but it's a good benchmark. I always change to a gear which prevents the vehicle running off on its own and then brake as and when required. As for heat build up try driving in Madeira - the brakes will end up almost glowing even with engine braking!!
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As I understand it, current recommendation is to use the brakes to slow the car, not the gears. However, when descending a hill it's ok to engage a lower gear so that a constant speed is more easily maintained, i.e. the engine braking effect is used to help keep the speed in check, but is not being used reduce the speed of the vehicle.
I hope that makes sense.
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Even modern brakes still suffer from brake fade, A sensible combination of both techniques would be advisable.
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It's not the gearbox doing the braking - that can't supply any stopping power, it is simply doing its job of transmitting torque. I never hear anyone say "don't accelerate" because that wears out the gearbox.
The engine supplies the braking power because on over-run with the throttle closed the pistons are pumping up and down in closed cylinders - like trying to pump a shock absorber, it absorbs energy.
And I can't see what harm that does either.
What people mean, I think, when they criticise "engine braking" is the old sports car technique of revving the engine, crashing into a lower gear, slowing hard, revving, down into a lower gear, etc. This always seemed to have as much to do with loving the sound of a burbling roaring exhaust note as to doing anything the brakes couldn't handle.
I use a mixture of engine and brakes. The same gear down as up is a good rule of thumb, with gentle application of the brakes at intervals just to keep the speed in check.
My rule is "anything gentle, good: anything sudden, hard or late, bad"
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The Gospel (1964)- Manual Police Driving Instruction:
Two methods of reducing speed:
(1) Deceleration of the engine as pressure on acc pedal is relaxed,
(2) application of brakes.
Three rules for all normal braking:
Brake only when travelling straight, that is not in a bend or when skidding. This means you must brake in plenty of time for whatever hazard you are approaching.
Let you brake pressure vary with the conditions of the road surface. Choose a coarse, firm and dry section of road for firm braking and ease off the pressure for a loose or slippery surface. This calls for continued observations of road surface conditions.
When decsneding a steep winding hill, maintain firm braking on the straight stretches, and brake as lightly as possible in bends or corners. Remember the value of engaging a lower gear at an early stage of descent.
Finally,when stopping, ease off brake pedal pressure as road speed is lost so that a car comes to rest on an even keel entirely without a jerk or settling down suddenly at the end.
Ok BR's out on the road and practice - lesson over.
DVD
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I like the rule others have given about use the same gear going down hill as you would up it. I've never really thought of it like that, but its something I automatically do. So often I'm following anotber car down a hill and they are braking all the way down to maintain a steady speed while I haven't touched the brakes once. I imagine their brakes will be red hot by the bottom of the hill, and they probably get through pads at a rapid rate too.
When it comes to the point of starting think about slowing down I always touch the brakes early, so in case something is not right with them, I've always got plenty of time to react. It certainly got me out of a whole when my master cylinder packed up at a very high speed while approaching a roundabout!
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