Same Engine, Different Cars

[barrycoll]

Hand brake turns require the left foot to de-clutch, so a foot operated hand brake would require two left feet.....anybody willing to own up?

[Sagitar]

...don't know of any car with rear disc brakes that uses some kind of auxiliary "drum" for the handbrake... The handbrake on such cars is simply a cable driven mechanical actuator which operates directly on the pads caliper; performing the same function as if you had used the hydraulics... (but only on the rear wheels)

I guess you haven't looked at many cars. Here is a quote from Wikipedia:-

"In cars with rear disc brakes, the parking brake either actuates the disc calipers (again, with much less force) or a small drum brake housed within the hub assembly (the inner circumference of the disc is often used instead of a separate drum)".

In some of the cars that were early adapters of four wheel disc brakes and used the rear discs alone for braking when parked, there were hand brake failures that resulted in runaway vehicles. The problem arose because as brakes cool the metal components shrink. In disc brakes the shrinkage of the disc takes the disc away from the pads, reducing the braking pressure. On a hill, this pressure reduction may result in the brake failing to hold the car, hence the runaway.

In drum brakes, the shrinkage pulls the drum more tightly onto the pads so that the brakes grip more firmly.

Even now, parking brakes that depend upon discs alone require careful maintenance and are likely to give trouble. Here is a quote from a car forum:-

"Disc parking brakes are never that good - which is why Mercedes Volvo etc which have disc rear brakes use a separate drum for parking brakes.

The problem of discs cooling and allowing the brake to become less effective is well known to vehicle designers - it is assumed that the contraction would be compensated for by the tension of the cable if the brake is applied firmly enough, and is allowed for in the newer vehicles with electronic parking brakes.

The MOT requirement for parking brake is 16% efficiency, being the 3rd line of braking, a threshold which I personally think is a bit low.

Most of the older vehicle handbooks used to advise you to put the transmission into’P’ on autos or 1st gear on manuals when parking on an incline - still good advice but somehow now omitted".

[MEP's Yaris GS]

Does anyone actually use the parking brake? I though it was only there as a legal requirement but pointless on the Prius.

In a year of ownership I've used mine about 4-5 times only, and only as a back up incase the Park gear fails. When in traffic etc, its normally a case of hitting the park button and then back into Drive when moving off. When parking just turn it off and it automatically goes into park.

[kithmo]

You'll break it if you keep hitting it

I hardly ever use my parking brake, probably 2-3 times a year just to make sure it doesn't seize, in fact I hardly use the P button, I just stop and turn the car off.

[APS]

Parking brake method - central drum inside a disk is probably the most common (or has been at least). Both my Corolla, Auris and I believe the Yaris has the internal drum brake setup. I have not had reason to look at the iQ yet (it does have rear disc brakes). But yes there are plenty of cars that have parking brakes acting on the discs too. 70' and 80's AlfaRomeos had it.

Citroën CX had a parking brake that acted on the *front* discs. A really complicated solution that needed frequent adjustment and some skill to make it effective. It had small secondary pads for the parking brake next to the main brake pads all housed in big 4piston caliper.

Regarding use of the parking brake - I use it all the time. Would never let the car be held by the gearbox lock alone. It's probably old habit. In old slush boxes we were always told never to let the locking pin which was actuated when putting it in P hold the car in any gradient as it would wear it and eventually could fail. Now I don't actually know exactly what the locking mechanism looks like on the HSD boxes but I would not be surprised if Toyota had made it very robust and reliable. I just prefer to find the car it he same place where I left it :) I may be totally over cautious. If nothing else I make sure the parking brake doesn't seize up.

Sent from my iPad using Toyota OC

[PeteB]

Does anyone actually use the parking brake? ...

Yup.

1. on my drive, which slopes quite steeply, to avoid putting strain on the Park pawl

2. when sitting parked in READY mode and I don't want the DRLs on

3. when stopped on a steep hill (elsewhere in the UK! - not often in Norfolk/Suffolk) before selecting P or N

Also, every 3 years I take a RoSPA driving test, conducted by a Police examiner - I always make sure it's set before he gets in the car - even on a car with a transmission 'park' facility, it's still technically an offence to fail to set the parking brake when leaving a vehicle.

[kithmo]

PeteB, re No.2 on your list, do your DRLs go off if you put the parking brake on in ready mode ?

[MEP's Yaris GS]

PeteB, re No.2 on your list, do your DRLs go off if you put the parking brake on in ready mode ?

No, once on they'll stay on until you power down, but if the parking brake is applied they'll only come on after power up once it has been removed.

[CPN]

...don't know of any car with rear disc brakes that uses some kind of auxiliary "drum" for the handbrake... The handbrake on such cars is simply a cable driven mechanical actuator which operates directly on the pads caliper; performing the same function as if you had used the hydraulics... (but only on the rear wheels)

I guess you haven't looked at many cars. Here is a quote from Wikipedia:-

"In cars with rear disc brakes, the parking brake either actuates the disc calipers (again, with much less force) or a small drum brake housed within the hub assembly (the inner circumference of the disc is often used instead of a separate drum)".

In some of the cars that were early adapters of four wheel disc brakes and used the rear discs alone for braking when parked, there were hand brake failures that resulted in runaway vehicles. The problem arose because as brakes cool the metal components shrink. In disc brakes the shrinkage of the disc takes the disc away from the pads, reducing the braking pressure. On a hill, this pressure reduction may result in the brake failing to hold the car, hence the runaway.

In drum brakes, the shrinkage pulls the drum more tightly onto the pads so that the brakes grip more firmly.

Even now, parking brakes that depend upon discs alone require careful maintenance and are likely to give trouble. Here is a quote from a car forum:-

"Disc parking brakes are never that good - which is why Mercedes Volvo etc which have disc rear brakes use a separate drum for parking brakes.

The problem of discs cooling and allowing the brake to become less effective is well known to vehicle designers - it is assumed that the contraction would be compensated for by the tension of the cable if the brake is applied firmly enough, and is allowed for in the newer vehicles with electronic parking brakes.

The MOT requirement for parking brake is 16% efficiency, being the 3rd line of braking, a threshold which I personally think is a bit low.

Most of the older vehicle handbooks used to advise you to put the transmission into’P’ on autos or 1st gear on manuals when parking on an incline - still good advice but somehow now omitted".

I'd appreciate a link to that page to have a read for myself? (update: not required, found it myself...)

I'd suggest you have a look at the attached photo of the rear of the caliper mechanism on my MY2015 Yaris Hybrid's offside rear brake disc in which you can clearly see the cable hooked on to the mechanical actuator which is attached to the end of the master hydraulic brake cylinder that compresses the pads when the handbrake is applied.... I'd also suggest this kind of mechanical override of the hydraulics is more common than you think. Oh, and by the way, I've worked as an engineer and mechanic on cars for over 45 years in motor sport and rallying so yes, I've looked at and worked on MANY cars...

[Sagitar]

...don't know of any car with rear disc brakes that uses some kind of auxiliary "drum" for the handbrake... The handbrake on such cars is simply a cable driven mechanical actuator which operates directly on the pads caliper; performing the same function as if you had used the hydraulics... (but only on the rear wheels)

I guess you haven't looked at many cars. Here is a quote from Wikipedia:-

"In cars with rear disc brakes, the parking brake either actuates the disc calipers (again, with much less force) or a small drum brake housed within the hub assembly (the inner circumference of the disc is often used instead of a separate drum)".

In some of the cars that were early adapters of four wheel disc brakes and used the rear discs alone for braking when parked, there were hand brake failures that resulted in runaway vehicles. The problem arose because as brakes cool the metal components shrink. In disc brakes the shrinkage of the disc takes the disc away from the pads, reducing the braking pressure. On a hill, this pressure reduction may result in the brake failing to hold the car, hence the runaway.

In drum brakes, the shrinkage pulls the drum more tightly onto the pads so that the brakes grip more firmly.

Even now, parking brakes that depend upon discs alone require careful maintenance and are likely to give trouble. Here is a quote from a car forum:-

"Disc parking brakes are never that good - which is why Mercedes Volvo etc which have disc rear brakes use a separate drum for parking brakes.

The problem of discs cooling and allowing the brake to become less effective is well known to vehicle designers - it is assumed that the contraction would be compensated for by the tension of the cable if the brake is applied firmly enough, and is allowed for in the newer vehicles with electronic parking brakes.

The MOT requirement for parking brake is 16% efficiency, being the 3rd line of braking, a threshold which I personally think is a bit low.

Most of the older vehicle handbooks used to advise you to put the transmission into’P’ on autos or 1st gear on manuals when parking on an incline - still good advice but somehow now omitted".

I'd appreciate a link to that page to have a read for myself? (update: not required, found it myself...)

I'd suggest you have a look at the attached photo of the rear of the caliper mechanism on my MY2015 Yaris Hybrid's offside rear brake disc in which you can clearly see the cable hooked on to the mechanical actuator which is attached to the end of the master hydraulic brake cylinder that compresses the pads when the handbrake is applied.... I'd also suggest this kind of mechanical override of the hydraulics is more common than you think. Oh, and by the way, I've worked as an engineer and mechanic on cars for over 45 years in motor sport and rallying so yes, I've looked at and worked on MANY cars...

So how does that alter anything that I said? Have a look here https://www.youtube.com/watch?v=lU6OKQxSg8U before you dig any deeper. To save some time go to 13:80 in the video.

[CPN]

I guess it's to do with the tone of the way you word things or perhaps I am misinterpreting...

Your line "I guess you haven't looked at many cars. Here is a quote from Wikipedia:-" could be interpreted as, "well you don't know much about cars do you? Here's something to show I'm right!"

You then quote a short paragraph from a much longer article about a "Parking Brake" (note that that term means it has been compiled by an American because in the UK "handbrake" would be the basic term - the term "emergency brake" is not even used in the UK) along with several extracts from other sites which could be described as opinion based at best... All to somehow try and assert that "the norm" for cars in the UK with rear disc brakes is to have a smaller auxiliary drum brake for the handbrake function whereas I would assert that the exact opposite is the case and that you will only find such auxiliary handbrake functionality (actually an emergency mechanical brake on the rear wheels) on expensive premium brand cars (Mercedes, BMW, Volvo etc) and not on volume manufacturers cars like those in the sub £15,000 market.

I also note that you come back at me with an American produced video of a car (Nissan Altima) that's not even available in the UK to demonstrate the inclusion of a small drum brake within a disc brake rotor assembly...

There have been many innovative ways of overcoming the temperature compensation problems to such an extent that it is not really a problem on today's cars. Toyota employs one particular method in its cars equipped with rear disc brakes and it works effectively and well. I'm sure that other volume manufacturers have employed similar methods where they would not want to add unnecessary cost to an already low cost product by adding a completely extra system on top of what is already engineered in for the inclusion of an "emergency brake" when our laws don't even require such a device's fitment; requiring only a conventional "handbrake" instead that is capable of holding the car still on an incline.

If I have misinterpreted your tone then you have my apologies.

[Sagitar]

I was responding only to your statement "...don't know of any car with rear disc brakes that uses some kind of auxiliary "drum" for the handbrake...". The italics on any are, by the way, yours.

Since there clearly are lots of cars with such an arrangement, I could only conclude that you had not seen them. Further, since I did not wish simply to assert that there are cars with combined disc and drum parking brakes, I tried to provide some reasonable evidence of their existence. I am sorry If you are unimpressed by that evidence, but I think that is your problem, not mine. I've given all the time that I am prepared to spare for this issue, so I'll say no more and leave it to others to judge whether or not there are cars that use combined disc and drum brakes for parking.

[CPN]

Clearly, my apology was neither appropriate nor necessary.

[Heidfirst]

handbags at dawn, gentlemen? :fishyface:

[Mkuk0]

If it helps I used to have a car with discs all round and a drum actuated handbrake, it was a Vauxhall Cavalier I think, 1990 vintage as I recall. I may be mistaken with the the year as I had a couple of Cavaliers, but I def had one as I used to service it meself and had no end of fun with the brakes