MikeD wrote:aqn: Exceptionally clear and helpful. However, on my last question about whether or not the "parking lock" is "safe enough" for most parking situations, I notice the following from the Owner's Manual: "CAUTION: To park the vehicle in cold climates, push the P position switch on the selector lever and place suitable chocks at both the front and back of a wheel with the electric parking brake released. If the electric parking brake is applied in cold climates, the brake may freeze and cannot be released.". So I gather both brake systems have their limitations and strengths.
Indeed. It's not uncommon for water to leak into the cable sheath of a cable-pulled parking/emergency brake. If you apply the parking brake in subzero temperatures, the water may freeze, leaving the brake stuck in the engaged position.
The parking lock ('P' in the "transmission") suffices for most situations, though I am in the habit of always engaging the parking brake, a habit from driving stick shift cars as well as a belt-and-suspenders thing. The owner's manual says to, with the foot brake depressed, "P-then-parking-brake" (page EV-18). It also recommends "parking brake-then-P" when parking on hills (page 5-20), so the parking mechanism's gear won't have to bear all of the car's weight.
Federal Motor Vehicle Safety Standards
MikeD wrote:It appears that one difference between those two brake systems is that the "parking brake" is designed so that it can be applied in an emergency while moving (say if the hydraulic brakes fail), whereas the "parking lock" is designed to be applied only when the car is not moving or moving very slowly.
Question: Would it have been less confusing if Nissan had used the terms "emergency brake" and "parking brake" rather than "parking brake" and "parking lock"? Which are the commonly used terms in modern cars today?
spell out three different brake systems: "service" brake i.e. the "normal" brake, emergency brake, and parking brake/parking mechanism/parking lock. Each must conform to separate requirements. They can be separate systems, or two of the three can be combined, but all three can not be combined. The parking brake and emergency brake systems are normally combined, hence the confusion about whether it's a "parking brake" or an "emergency brake".
The emergency brake must be frictional (see my post above) and must be functional when all else fails: hydraulic failure, failure of main electrical system, ignition off, etc.
You can apply the parking brake while moving
MikeD wrote:Has anyone tried out applying the "parking brake" while moving at speed? I don't suppose the parking brake switch provides any control on the braking force/speed ?
: pull up once to engage, pull twice to really
engage. You have
to be able to apply the parking/emergency brake while moving, otherwise it's not an "emergency brake"!
MikeD wrote:I don't suppose the parking brake switch provides any control on the braking force/speed ?
The LEAF's parking/emergency brake provides a little bit of control over application force: pull up once to engage, pull up twice (doubleclick) to really
Ingineer wrote:FYI: The Brake capacitor has nothing to do with the parking brake system [...]
If the 12v system is offline, you will not be able to [...] engage the parking brake, but you can disengage it from the manual release. [...]
The Hydraulic brakes will still function normally for a handful of stops until the capacitor depletes, [...]
I would tend to agree with that. I checked the service manual. All references to a "brake power supply backup" are in the "BR Brake System" section, not in the "PB Parking Section". (I edited the title to reflect this info.
) However, now the question becomes: which is the emergency brake on the LEAF: the service brake, or the parking brake?
Ingineer wrote:I suspect there is at least 10 watt-hours of usable energy (12v output) in the brake capacitor. At some point I'll do an accurate test.
That would be interesting information.
This is in the service manual, page PB-17
BnBinSD wrote:In the Owner's Manual, the parking brake is mentioned several times. In the first mention (I think), it states to "apply the parking brake twice for maximum effect" or some such, but in subsequent discussions - especially parking on hills, it's never mentioned again.
: "Pulling the parking brake switch again increases the parking brake braking force (increases the rear cable tensile force)."
I would think it's in the owner's manual as well, but I don't know for sure.
GroundLoop wrote:Emergency Brake is not quite right, since it's not used in emergencies. Unless it's a big handle you can yank and slide the rear, I just don't see it being that useful in crisis.
Having a longish handle to apply and modulate the parking brake might be nice, though at the end of the day, I only care that the "emergency" brake be capable of stopping the car if the service brake fails. I don't care if I have to yank a big handle or whistle Dixie to activate it!
That said, the only gripe I have about the LEAF's parking brake is that it only has three settings: off, on, and REALLY on, and there is no room for modulation in between.
GroundLoop wrote:Is there something legitimately called a "transmission" with one gear? If so, then tranny lock sounds correct to me.
It's got gears and it "transmits" power from the motor to the driveshafts. I'd call it a "transmission".