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(updated the change the term "sliding" to the, in this case, more correct "rolling")

About parking a car with a manual transmission on a sloped surface:

  1. Is it normal that the car starts rolling downhill if only the parking brake is applied and the gear selector is left on neutral?
  2. Is there any difference between leaving the gear selector on reverse vs. any of the forward gears?
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    To keep it from sliding, buy better tires and avoid ice. – Peter - Reinstate Monica Jun 2 '20 at 11:08
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    Reverse is the lowest gear, so best choice. Some cars (Saab) wouldn't let you remove the key unless you were in reverse. The bonus was a surprise for anyone hotwiring it... – user_1818839 Jun 2 '20 at 14:02
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    Parking brake is on the rear wheels so leaving it in gear adds two more wheels' traction to the total braking force, if your car is front wheel drive. – user3528438 Jun 2 '20 at 16:48
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    It is not a "Parking Brake" (at least in the UK). It is legally an "Emergency Brake" for use when the primary braking system fails. It is mandatory at all times that it can provide braking effort exceeding 25% of the vehicle's weight, and failing this at an annual test voids your permit to use the vehicle, immediately. – Paul_Pedant Jun 2 '20 at 17:17
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    @Paul_Pedant The UK MOT test (mandatory vehicle safety check) guidance refers to the 'parking brake' (gov.uk/guidance/…), and the highway code the the 'handbrake'. I never hear it called the 'emergency brake'. Your comment reads like it is not intended for parking. In fact it is a legally required to be used whenever parking the vehicle.(Rule 239 - gov.uk/guidance/the-highway-code/waiting-and-parking-238-to-252, where MUST denotes a legal requirement) – Andy Hames Jun 5 '20 at 15:45
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It isn't normal that the car moves downhill with the parking brake applied, if it does it shows that the parking brake isn't working properly. It should fully stop the car even when on a steep hill. This can be caused by worn brake shoes, the cable could be stretched out or the mechanisms are worn, all are (generally) straightforward to fix. It's a safety issue that will make your car fail an inspection, and rightly so, if it won't stop your car from rolling down a hill it won't stop your car if your main brakes fail.

As to reverse and forward there is no single answer. What I was always taught, and what was in the NY State DMV handbook when I took my driving test many years ago was to put the transmission in reverse gear when parked downhill and in a forward gear when uphill, this is so the car rolling will work against the engine's normal rotation. In older cars this was important as spinning the engine could cause it to start without the ignition being turned as they had mechanical fuel pumps and ignition systems. Newer, electronically controlled engines won't run without the computer so this isn't an issue and you are better doing the opposite as may damage the engine. So in a newer car put it in reverse going uphill and first going downhill.

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    If your parking brake won't hold you on the hill, how do you intend to start the vehicle and drive away, unless you have three feet to operate all the pedals at the same time? Leaving the car in gear is dangerous, because if you forget to take it out of gear, operating the starter will move the car, and if the engine fires then releasing the starter won't stop you before you crash into something. – alephzero Jun 1 '20 at 21:10
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    @alephzero From a country where manuals are common, the advice regarding which gear to choose is the same as this answer (except that I've never heard about the 'new cars get damaged by going for the opposite direction gear' and the two 'official guides' I quickly googled still have that rule without any such mention. Perhaps it applies mostly to fancy electric cars, but pretty surely not to every car from 1960). But yes, broken handbrake ->straight to the mechanic before parking at any hill. – Frank Hopkins Jun 2 '20 at 1:14
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    @alephzero From another country with commonly used manuals. While operating the starter with gear engaged will move the car indeed, such situation it is very rare to happen, it is more of anecdotal situation. Anyone driving manual checks the gear lever is in neutral before starting the car. It is also common to keep brake pedal pressed, just for the sake of safety. And newer cars, with button start, require the use of clutch pedal to start the car. So generally, there is no big deal leaving car in gear. Some leave car in gear all the time, not just on hills. – Alex Jun 2 '20 at 6:40
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    @alephzero if you have a car with a manual transmission, that means you also have a clutch pedal to prevent exactly this. – Tom Lint Jun 2 '20 at 8:01
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    @alephzero, leaving the car in gear isn't dangerous in itself. Starting the car without checking it's on neutral and/or that you're standing on the clutch is what is dangerous. And if you ever drive cars other people use, too (be it a family car or one of your friends), you better learn to check it, because you can't count on them doing what you expected. I'm pretty sure they teach you that in driving school too, but it's been too long. – ilkkachu Jun 2 '20 at 11:18
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The parking brake should hold the vehicle, otherwise it can be difficult to achieve a hill start.

When parking, the front wheels should be turned into the kerb so if it rolls it runs into the kerb and stops.

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    Nice and to the point, but also: Either first or reverse gear should be set. If you only go for the handbrake - or only for putting either of those two gears in, you might be liable to your insurance company if your car rolls off and damages something in some countries. And it needs to be the first or the reverse gear, higher gears provide less resistance. So it makes a difference which gear you choose! (And again liability can hit you over the head if you pick a higher gear). – Frank Hopkins Jun 2 '20 at 1:20
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    The direction you turn the the tire depends on the car orientation and the side of the hill you are on. – eps Jun 2 '20 at 13:20
  • @FrankHopkins Hmm, my car has a 4WD extra-low gear, I've just been leaving it in the regular 2WD 1st gear, I wonder if I should leave it in extra-low. I'm a bit concerned that if I get towed they will destroy the transmission. – JBGreen Jun 2 '20 at 21:30
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    @JBChouinard don't leave it in a place where it will get towed... then there won't be any risk to the transmission. – Solar Mike Jun 2 '20 at 21:41
  • @JBChouinard law-wise I think the regular 1st should suffice (no legal expert though^^) and no idea how towing companies deal with full 4wd anyway, they likely have to lift up all wheels in such a case I would guess (pure guesswork!^^). Btw. I've heard in Italian cities it's often typical to neither use the handbrake nor a gear when parking between other cars so your car can be pushed back and forth to make room when people come and go. Not sure if it's an urban legend or true, but if true then only applied in flat areas obviously^^ Maybe an Italian can verify. ^^ – Frank Hopkins Jun 2 '20 at 21:51
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The way I was taught in driving school is this:

  1. Pull the handbrake (this is obvious)
  2. Put the car into gear (1st or reverse are recommended) in case the handbrake fails. The gear does not matter that much though and any would work in the end, because compression is what keeps the car from moving. When the wheels start rolling, the gearbox transfers that motion to the engines and pistons, one or more will eventually compress the air in the combustion chamber, the pressure resisting the rolling of the wheels, and the car stops
  3. Finally, turn the wheels towards the kerb. In case all of the above fail (highly unlikely), the car rolls and stops into the kerb/fence/whatever is on the side of the road and not in the middle of the road/traffic/pedestrians/etc.
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    "The gear does not matter because compression is what keeps the car from moving" in low gear, the engine offers more resistance than in high gear. This is why people recommend putting the box in first or reverse gear rather than fifth. – Hobbes Jun 2 '20 at 9:25
  • @Hobbes , edited to reflect the recommendation for 1st and reverse. – Adrian Sicaru Jun 2 '20 at 9:50
  • "The gear does not matter that much though and any would work in the end, because compression is what keeps the car from moving" - if this were the case, bump starting a car would be impossible. It is not, so therefore.... – Moo Jun 3 '20 at 0:16
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(Assuming that "sliding" is an unintentional wording. Unless the street is frozen with ice, a car normally never slides downhill.)

If the gear is in neutral (i.e. no gear engaged) then it is very normal for the car to roll downhill if the parking brake is not engaged.
If the parking brake is engaged and the car still rolls downhill, the brake is either broken or adjusted badly. In either case, this needs fixing.
Modern parking brakes are a kind of nuisance in that respect because nowadays everything must be "smart" with microchips, blinking lights, and little electro motors. On a "traditional" parking brake, there's an iron wire attached to the lever with two screws. Open screws, pull cable a bit tighter, close screws, done. On a modern brake, prepare to pull your wallet.

That being said, the parking brake, in my opinion, shouldn't be used for parking in the first place. Yes, your driving instructor tells you that, but either way...

The first gear is mighty fine for holding your car in place. The reverse gear also works, and in theory would be "even better" (some super smart cars indeed force you to use that one), although when something is already perfectly good, then there is no such thing as "even better".
The first gear is preferrable insofar as it is easier to engage, less obnoxious to the transmission levers, and less irritating to other traffic participants. And since it is just good enough, there's no need to do anything else.
I've used nothing else for two decades (well, I'd say 3 decades, but since about a decade I'm only driving on manual transmission occasionally so that doesn't count).

The reverse gear is more difficult to engage, it will cause the white light on the back of your car to light up (which is irritating to others!) and it is more stressful overall.

The parking brake has the downside that if you engage it during winter (outside, not in your garage) and you come back some hours later, you may get a funny surprise for free because now your car is unusable with a frozen-up parking brake. Likewise, if you park your car with parking brake engaged and something happens (something, anything, like... you go to hospital or on holiday) and you leave your car there for a couple of weeks, you may equally get a nice surprise upon returning. Usually an unpleasant, scary noise as the brake breaks free. While not a real problem, it's more scary and annoying than it needs to be.

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  • thank you for the explanation! and yes I should have used the term "rolling" instead of "sliding". I have now corrected that in the question. – user100487 Jun 2 '20 at 18:34
  • Unwanted surprise also can be caused by disc brakes rust-lock because they are still engaged until the wheel turns. Let the car stay there long enough and troubles with handbrake are of second order nuissance... – Crowley Jun 2 '20 at 19:07

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