For some reason I seem to think that it’s illegal to coast in neutral down a hill, in either a manual or automatic transmission. This may be a Canadian provincial or federal law, or it may be bullocks. However, now I’m wondering why it would be illegal? I would suppose this kind of law would somehow be based on potential danger, but what danger?
Anyone have any insight?
Dunno if it’s illegal, but the reasoning I’ve heard against it was based on the inability to apply engine braking and also the extra action/coordination (potentially causing flusterment) that would be necessary if, for some reason, you suddenly needed to apply power.
I do it all the time (well, actually, I just hold down the clutch) - part of my economy driving strategy that gets me (on a good day) upwards of 60 MPG
Illegal or not, it is a bad idea to drive down a hill/mountain pass with only one mechanism to contol your speed.
Also, on rear wheel drive vehicles. it will significantly reduce the life of the bearings in your transmission and differential. Don’t know about damage to front wheel drive.
It’s a dangerous practice, but I don’t know about illegal. It would be hard to prove someone did it intentially, unless they admitted it, or there was a witness in the vehicle.
It’s a lot cheaper to use your brakes as brakes than to use your engines as brakes.
If the car is in gear and you hit the brakes, you’re more likely to stall. Besides, if the brakes fail, it’s much quicker to use the emergency brake to stop the car. Further, if you were actually going to use the engine to stop the car in a hurry, you would need to disingage the clutch anyway so you could shift into a low gear.
Depends how you did it. When I have used the engine as a brake, I have found myself applying gas more frequently to counter the braking effect of the engine.
In the UK, you could be charged with not being in full control of the vehicle. I can’t imagine how it could be enforced though.
Total nonsense! Why would it cost anything to use the engine compression to slow the vehicle?
You’re not going to stall the engine, on a downhill, by applying the breaks, unless you come to a stop w/o using the clutch.
If the downgrade is very slight, you may need power to maintain speed, on any significant downgrade, the vehicle will gain speed w/o power.
The more times the engine turns over, the more wear on the engine. Further, if power is transmitted through the transmission, it adds to wear on the transmission. Finally, though I’m not an automotive engineer, I would guess that a car is designed mainly to transmit power from the engine to the wheels, not vice versa, and therefore the latter puts even more wear on the car.
I would think that slowing down to 10 miles an hour while in 5th gear might do it. Personally, I always throw out the clutch while applying the brakes. But using both the engine and the brakes as brakes sort of assumes that you aren’t doing this all the time.
A lot of downgrades vary in slope and direction. So you need to be slowing down and speeding up appropriately.
For normal flat-terrain driving, sure. But it’s a lot safer to have engine braking available when going down a hill of any significance.
Except emergency brakes (assuming they work - many don’t) are likely to fail from overheating even faster than the service brakes, and the whole point is to avoid any brake failure in the first place by letting engine compression mitigate runaway rolling.
Presumably the emergency brakes won’t start overheating until you actually engage them. If that won’t stop the car immediately, it’s hard to imagine what will. But at that point, there’s nothing wrong with putting the car in gear.
Totally sensible. Engine braking drives the RPMs up, accelerating engine wear over the life of the engine. Brake pads are cheap. Ring and valve jobs are not.
What kind of vehicle are you talking about? In passenger cars the emergency brake *is * the service brake–it’s usually just another handle connected by a cable instead of the hydraulics to the rear brakes.
You’ve never had a car get away from you going down a long and/or steep hill, have you?
Many emergency brakes are just a different application of the same shoes or pads used for the service brakes, and will already be overheated. Those that use separate shoes use really small separate shoes (which brings us to the reason they’re often called parking brakes - they aren’t designed to stop a moving vehicle) which will overheat in very short order. And as previously mentioned, putting a runaway car into gear is usually physically challenging (significant mismatch of transmission shaft speeds) and being attempted under duress. It ain’t that easy.
Most “emergency” brakes are mechanically linked to the rear wheels only, thereby reducing your braking power by half. They are not very effective at stopping, especially at higher speeds and on a downgrade.
If your vehicle is rapidly gaining speed on a downgrade, you may not be able to get it into gear, especially a lower gear.
Only thing I can think of is engine driven lubricant pumps. Engine RPM drives the lubrication systems, higher speed = more oil circulation. I am not sure of the exact mechanics of lubrication within an automatic tranny but if its driven by some kind of PTO on the input side of things you might be inadequately cooling/lubricating your transmission when rolling at idle in neutral at high speeds.
Bad presumption boygenius. The overwhelming majority* of E-brakes utilize the rear service brake friction components, just activated by a mechanical system in parallel with the hydraulic system of the service brakes. The utility in an emergency is limited to failure of the hydraulic system. If you cook the service brakes, you have also rendered the E-brake useless.
-on preview, just emphasising what Gary T already said.
*Some modern cars with disk rear brakes have a separate parking brake system. These are always of far lower capacity (braking force, heat capacity, lining thickness, etc) than the service brakes. They are really intended as a parking brake.
The definition of service brake is that which is applied by the brake pedal in normal driving. The definition of emergency/parking brake is that which is applied by the separate pedal or lever designated for that purpose. So by definition, the service brake is NOT the parking/emergency brake.
Now it’s true that most designs use the same shoes or pads for both systems, but many cars with rear disc brakes have separate drum-type parking brakes. Nevertheless, practically speaking you’re right that often it’s the same linings being used, but my point still stands - on a runaway car with overheated brakes, the parking/emergency brake will fail faster than the service brake did. If they use the same linings, “faster” can mean “instantly” (as they’ve already failed).
We are not talking about using your engine to reduce speed, we are talking about maintaining a steady, controllable speed without cooking your brakes. Your car’s engine is very well suited for this job. An added bonus would be that your car uses less fuel than when you would let it idle.
Actually, it’s even worse than that. Rear brakes typically account for 25-40% of the total stopping power.
Right on both counts.
On a small hill it’s probably no big deal one way or the other. Even the extra wear and tear on the engine and transmission probably doesn’t amount to all that much. After all, you are adding extra wear and tear on parts that are designed to move the entire weight of the car around all day long every day. It’s not like you are significantly overstressing anything.
On a large mountain, though, relying only on your brakes can cause the brakes to heat up, which I have heard can cause the brake fluid to boil. Once that happens you effectively don’t have brakes any more, and stopping becomes a bit more of a challenge.
Coasting in neutral is illegal in some areas. A quick google confirmed that it is illegal in Alabama, Rhode Island, and Washington State. There are lots of sites that say it is illegal in “many” states but I didn’t turn up a comprehensive list in the short time that I googled.
The reasons that I’ve always heard for the laws were pretty much as Mangetout stated.