Toyota brake master cylinders and proportioning valves

[PeteH]

Takai,

Thanks, but do you know if the handbrake system is dual circuit?

Pete

[takai]

No idea if its dual circuit, i wasnt under there looking at the brakes mainly. Wheel bearing was shot.

[WDE_BDY]

Possibly not relevant, but here is the NZ perspective -
Hydraulic handbrake is only road legal in two situations.
1. There is a cable backup
2. In approved competition cars (mainly rally cars that must be road legal for touring stages). However they must carry wheel chocks in the vehicle for when parked, and this is checked at each roadworth inspection (every 6 to 12 months).
The reasoning is that hydraulic braking systems are not designed to hold presure for an extended period of time, park on a hill and your car may still be there in 1 hour but will it be there in 1 day, 1 week, 1 month? It has nothing to do with the ability to assist in an emergency stop if the hydraulic system fails.
Note this applies only in NZ. I will be running cable and hydraulic in my car.

Callum

[petergoudie]

To continue my comments:

1) I spoke to the person who did the ADR compliance tests for Ferrari & Aston Martin as well as a person who did some work on a 3200GT Aston.

The emergency/parking brake system is electric over spring. It is held OFF by a motor and the spring force applies and holds it on. If for some reason the battery splits at exactly the same time the engine stalls and all power is lost, the emergency brake applies with the spring force. For parking, a switch turns the power off. The same principle is used on heavy vehicles fitted with air brakes - spring applied, compressed air held off.

2) The interpretation that the NCOP and other rules only apply to the ratchet mechanism is a nice try to avoid the truth but it is wrong. If anyone has an engineering approval for such a system, go and replace your handbrake system or fit a second mechanical one. Also, I don't think any of those said to be OK in the above comments would have a written approval or sign off from any of the registration authorities.

3) If you still disagree with all this, I hope you all made comments on the NCOP as the comment period closed a few weeks ago. You will note I made the Toymods forum aware of this in the NCOP threads.

I think I'm owed an apology because of the comments made above. If you want to use a hydraulic handbrake system, rather than saying nasty things about those who are trying to help you, start writing letters to all the State & Territory registration authorities to change the rules (you will need a good case though, if there is one).

[PeteH]

Hi,

Thanks for clarifying how the Aston Martin & Ferrari park brake system works. I would have been very surprised to learn that it was just a simple hydraulic system with no fail safe.

Pete

[YLD-16L]

Nice work on the clarification of those facts Peter.

In many cars now like the Prius with a ratcheting foot brake for parking/emergency stops that needs maximum application to disengage, how could it be seen as a form of emergency stopping device?

In the split second event that it was needed to be used in a hydraulic brake failure situation you only get one chance to apply it to a point where it slows and not locks the wheels, go to far and you have to lock the brakes to release it. I doubt 99% of people would have the skill to get it right in that situation as you only get essentially one shot at it if the vehicle needs to be stopped immediately.

Great for parking but surely not seen as an emergency stopping device unless I have missed some aspect of how this particular system works??

[PeteH]

In many cars now like the Prius with a ratcheting foot brake for parking/emergency stops that needs maximum application to disengage, how could it be seen as a form of emergency stopping device?

In the split second event that it was needed to be used in a hydraulic brake failure situation you only get one chance to apply it to a point where it slows and not locks the wheels, go to far and you have to lock the brakes to release it. I doubt 99% of people would have the skill to get it right in that situation as you only get essentially one shot at it if the vehicle needs to be stopped immediately.

Great for parking but surely not seen as an emergency stopping device unless I have missed some aspect of how this particular system works??

Hi,

I am fairly certain that the park brake is just that and is only meant to be applied to hold the car when it is stationary. The second circuit of a normal dual circuit braking system is the "emergency" part of the braking system.

Pete

[YLD-16L]

Hi,

I am fairly certain that the park brake is just that and is only meant to be applied to hold the car when it is stationary. The second circuit of a normal dual circuit braking system is the "emergency" part of the braking system.

Pete

That was my point, hence why is it being referred to as an emergency brake in this thread?

As you noted, on a dual circuit system the working circuit is the backup for the failed circuit and if the handbrake isn't part of the emergency braking system then this whole debate about hydraulic handbrakes replacing them as an "emergency brake" is getting into a bit of a circular argument with no real point, save for the NCOP requirements and stationary parking of course.

[PeteH]

Hi,

I think the problem here is the term "emergency brake" is being used where in fact "parking brake" is the correct term. Just having re-read my posts I notice I am also guilty of mixing these terms.... ..... will go and correct my previous posts for anybody just tuning in.

In regards to the hydraulic handbrake debate to me it is about the suitabiltiy/legality of a standalone hydraulic system for use as a park brake in lieu of a system failsafe or cable (OE) handbrake. Not whether a hydraulic handbrake will perform as a backup in the event of total failure of the primary brake system.

Pete

[YLD-16L]

Thanks for the clarification PeteH, if we're all using the same nomenclature that clears up that part of the discussion.

In regards to the hydraulic handbrake debate to me it is about the suitabiltiy/legality of a standalone hydraulic system for use as a park brake in lieu of a system failsafe or cable (OE) handbrake.

Suitability is debateable to some extent based on the vehicle use, the legality of it is black and white .

I don't think that fitment of a hydraulic handbrake on a dual circuit system is quite as bad as this initial post eluded to............ "A hydraulic handbrake only, is a good way to kill yourself or someone else or lose your car down a hill."


Multiple unrelated simultaneous failures would have to occur to end in a result so dire.

[PeteH]

Thanks for the clarification PeteH, if we're all using the same nomenclature that clears up that part of the discussion.



Suitability is debateable to some extent based on the vehicle use, the legality of it is black and white .

I don't think that fitment of a hydraulic handbrake on a dual circuit system is quite as bad as this initial post eluded to............ "A hydraulic handbrake only, is a good way to kill yourself or someone else or lose your car down a hill."


Multiple unrelated simultaneous failures would have to occur to end in a result so dire.

Hi,

Ahh yes but some are arguing suitability while others are arguing legality so I'm just covering both......trying to make all feel loved..

I disagree with your second paragraph. The handbrake and normal service brake are two seperate systems. If you only relied on a hydraulic handbrake to hold your car on an incline and this hydraulic system failed, with no body in the car, it is correct that you would lose your car, and it is also feasible that somebody could be injured. And being a hydraulic system, activated by a piston locked into a fixed position, I am certain that it would lose pressure over time and therefore lose its effectiveness.

I think that is the point that petergoudie was trying to make in his initial post, and one that I agree with.

And yes circular argument...

Pete

[YLD-16L]

I just read what you quoted above again and I must admit my first take on PeterG's quote where he says "losing your car down a hill" I took it in the sense of a brake failure while driving and then relying on the handbrake to pull up but now realise he was probably (??) referring exclusively to a parked car running away in the event of hydraulic handbrake failure.

To which I totally agree with his statement in that case.

[1JZ-Rolla]

hmmm, hasn't this just snowballed! Good discussion in the context of black & white interpretation for sure (in the eye of RTA/ADR legalities and approval), but in the practical sense some form of "fit for purpose" approach should be taken perhaps, particularly for vehicles of a "rally rego" type configuration.

2 aspects exist: that of a braking system's ability to hold a parked vehicle, and that of being able to stop a vehicle safely and in a controlled manner in the event of hydraulic failure. I don't think we'll be able to fully address the 2nd one... other than to agree that some form of retarding the vehicles speed somewhat may be of some benefit to what extent depends on the vehicle in question, and the driver's skill.

No need for apologies, opinions are like arseholes, everybody has one and they are all full of shit take everything with a grain of salt as we are all capable of dropping the odd heavily-influenced statements on the intahwebs from time to time


[edit] by the way, are Pete and Peter one and the same? an single entity under two identities?

[PeteH]

Hi,

Snowballed would be the apt term and I would say there may be a bit more discussion if Linden rechecks this thread..

I'll conceed that a "fit for purpose" application would be fine. But in the context of this forum, and it's members having predominantly road based vehicles, the discussion for and against has offered up some really good information that may be useful to somebody considering a hydraulic handbrake for a street car.

oh and just if anybody is wondering.....Peter Goudie and myself are not one and the same. We are just two Peters with a common view......

Cheers,

Pete

[WDE_BDY]

Hi,

And being a hydraulic system, activated by a piston locked into a fixed position, I am certain that it would lose pressure over time and therefore lose its effectiveness.

Pete

Which comes to back the New Zealand example I gave and why they have very limited legality here.

Callum