Toyota brake master cylinders and proportioning valves

[1JZ-Rolla]

I'm looking to make some changes to my brake hydraulic system, removing the factory proportioning valve, adding a hydraulic handbrake, different rear discs, and wilwood proportioning valve in my AE71 corolla.

From factory, this car uses the same style of proportioning valve as other corollas and celicas of the era, with two lines in (front & rear) and 3 lines out (1 rear, 2 front).

So the question is, does Toyota have any form of residual pressure valves in either this proportioning assembly, or the master cylinder itself? or should I add aftermarket ones to the brake lines?

Cheers
Phil

[petergoudie]

Hydraulic hand brakes are illegal if you do not have a second mechanical one fitted. A hydraulic handbrake only, is a good way to kill yourself or someone else or lose your car down a hill.

[YLD-16L]

I'm looking to make some changes to my brake hydraulic system, removing the factory proportioning valve, adding a hydraulic handbrake, different rear discs, and wilwood proportioning valve in my AE71 corolla.

From factory, this car uses the same style of proportioning valve as other corollas and celicas of the era, with two lines in (front & rear) and 3 lines out (1 rear, 2 front).

So the question is, does Toyota have any form of residual pressure valves in either this proportioning assembly, or the master cylinder itself? or should I add aftermarket ones to the brake lines?

Cheers
Phil

You won't need a residual valve Phil, to quote Willwood:

"Available in two sizes, 2 lb. and 10 lb. The 2 lb. is used when the master cylinders are mounted below the calipers. This keeps the brake fluid from draining back to the master cylinders so you don't have excessive pedal travel and caliper restriction. The 10 lb. valve is used to compensate for return spring tension in drum brake setups."

I looked into all this when I changed my whole brake setup.

[1JZ-Rolla]

petergoudie: care to elaborate why i'll be likely to end up in the newspaper obituaries?

Thanks Shano, won't fit them to my vehicle in that case.

Cheers

[PeteH]

petergoudie: care to elaborate why i'll be likely to end up in the newspaper obituaries?

Thanks Shano, won't fit them to my vehicle in that case.

Cheers

Hi,

I think what Mr. Goudie is alluding to is that in the event of a loss of line pressure in your hydraulic handbrake, i.e. flexible line failure, leaking system, etc, you will have no handbrake. If this is your sole parking brake this could be a big problem.

Pete

[The Real Roadrunner]

Hydraulic hand brakes are illegal if you do not have a second mechanical one fitted. A hydraulic handbrake only, is a good way to kill yourself or someone else or lose your car down a hill.

illegal? since when? i respect the fact that you are ex-rta but spreading mistruths is something im not a fan of.

A vehicle may be fitted with a hydraulic handbrake provided that its not integral with the foot pedal braking system, ie a seperate caliper for handbrake is required.

If you still think its illegal i suggest you stick your head under some ferrari's and aston martins when you get a chance as it may change your mind , these cars have passed the required ADR's and are road legal therefore if i chose to copy it why should i not be allowed.

Why is a cup seal any more likely to fail than a cable? if you think it is then ill await your report wanting to ban all roadgoing vehicles until they revert to a cable braking system at all corners (can you imagine the awesome pedal feel it would provide )

ive had hydraulic handbrakes fitted in a few of my cars and i never once had an issue with it that was line pressure related or bleeding off related.

why would you cause a death or lose your vehicle? a frayed cable could cause the same thing if it went unnoticed till it snapped (and your foot brakes miraculously fail at the same time) why are they still legal?

Im not trying to be arguementative but a statement like yours needs a thorough explaination as to the exact reasons why, and im pretty sure i rebutted most of them in this post anyway.

cheers
linden

[1JZ-Rolla]

How about a poll, since the mere mention of a hydraulic handbrake must mean that imminent death is near?

Who has experienced (first hand) a hydraulic brake system failure in a well maintained car? No, not your mate's-grandmothers 120Y that has not seen spanner in 22 years, but a car that has actually been the subject of preventative maintenance, ie: fresh fluid, good MC & caliper seals, quality flex hoses etc etc? These components are cycled more times in a year than you could count, yet their reliability is pretty much faultless if regularly inspected and maintained.

What would it take for a car like this to have a failure that requires use of the cable operated emergency hand brake? and if so, what are the chances that the handbrake will actually retard the vehicles motion sufficiently to avoid a collision?

Not arguing at all the fact that a cable operated backup braking system has its merits, it certainly does... but it is limited in its effectiveness, and the likelihood of needing it is minimal perhaps?

[The Real Roadrunner]

Im yet to have one.

the only time ive ever had cup seal related problems is with S/H masos being blead incorrectly and that is a maintanence/missuse problem.

Stock handbrakes aren't much chop hence why i like hydraulics, the feel and power they provide is much better but as the rear of the vehicle doesn't do alot of the braking they still won't help much in accident aviodance.

cheers
linden

[petergoudie]

I would like to say it was illegal since the Motor Traffic Act, 1909 (the first set of road related rules in NSW) but hydraulic brakes were not put into mass production until about 1927 by Walter P Chrysler. There were, however, some hydraulic systems available from small time manufacturers and some used water with leather bags behind the shoes. As I understand it, they all had problems until Chrysler perfected the system although it was most likely Bendix or Westinghouse that did the work for him.

It is, however, entirely possible that hydraulic parking brakes (later called emergency brakes as the ADRs came into place) were made illegal in the Motor Traffic Regulations, 1935 (the first set of motor traffic regulations in NSW).

There are two sorts of hydraulic parking brakes around one of which was mentioned above.

That first type is simply a needle valve on the road braking system that stops the fluid returning to the master cylinder when the foot pedal is depressed. These are still sometimes fitted to off-road mobile cranes although there are particular requirements to their operation. Over the years, some persons had fitted this type of parking brake to cars but were asked to remove them and to fit a mechanical hand brake. I remember seeing one fitted to a fully home made car something like a Lotus 7, possibly in an effort to reduce unsprung weight.

The second type is the full hydraulic brake with its own master cylinder on the handbrake lever. The only vehicles which gained approval to use these were a few road registered rally cars which had also retained the standard mechanical brake. Others might have been fitted to vehicles with Engineering Reports and the RTA would have never seen them but the Engineer should have made sure a mechanical parking/emergency brake was fitted before signing anything off.

In regard to those Ferraris & Astons mentioned, I think you will find they have a mechanical handbrake system except it operates on a lever & cam or a very coarse screw thread inside the hydraulic service brake calliper. They wind one of the brake pistons in and I presume they are a sliding type calliper so the other pad makes contact. The coarse screw thread type is like the disc brakes on some bicycles. As I recall, Citroen DS & ID models had a separate mechanical calliper for the hand brake and I have an inkling the Alfa Sud used something similar. They did all this on the front discs as being front-wheel-drive all the weight is on the front. Also, a number of the recent model Fords have a rear calliper where the piston has to be wound back in to fit new pads.

Below, I’ve taken an extract from the NCOP which will basically reflect the ADRs and the current Regulations in every State & Territory.

‘In the applied position, retention of the park brake system must be by mechanical means.’

[takai]

Unless they change them in bringing them over here (which i doubt) DB9s (and 7s too i think) use a separate hydraulic caliper with a hydraulic ratchetted brake. In any case pretty much all current Ferarris and Astons have twin piston opposing hydraulic rear calipers (some have quad piston rears), this pretty much negates being able to use a screw type design as is in use on some smaller cars (Corollas etc)

Below, I’ve taken an extract from the NCOP which will basically reflect the ADRs and the current Regulations in every State & Territory.

‘In the applied position, retention of the park brake system must be by mechanical means.’

The interpretation of the NCOP which you quote that i have been given by several gingerbeers, and also two of the South Australian RTA folk is that the retention mechanism referred to is the ratchet to hold the park brake in place, not the brake itself.

Anyway back to the original question, in the race car i have none of the stock proportioning valves left. Fronts run MC>T-piece>Caliper, rears MC>Wilwood Valve>Hydro Handbrake>T-piece>Caliper.
P.s. i havnt died in a fire, or been in the papers for killing anyone yet. I keep a chock for all the 1 time i have had to hold the car on an incline.

[web]

The point is that a hydraulic handbrake is safe as long as it has its own circuit, completely independent from the foot brakes. That means extra lines and cylinders.

Even the electric handbrakes fitted to many current new cars are legal worldwide. They are not required to be cable operated or mechanical. That's probably a mis interpretation or oversimplification of the rules. The rule seems to be that they need to be completely independent from the foot brakes - how they achieve that is unimportant. A whole second hydraulic circuit (Ferrari, Aston Martin), electric (new VW's, Renaults etc) or cable, it's all fine as long as it's completely independent from the foot brake circuit.

For a cheap but slightly "outside the box" option you could consider using some Volvo front calipers in the rear. Some come in a two pot variety with one hose per pot - on triangularly separated circuits. Each half of the master cylinder operates one pot on each front caliper, and one rear caliper. So each circuit brakes three wheels. This was only done on 700/900 series Volvos without ABS. Maybe 200 series as well, not sure. If you use just one piston of one of those calipers for the foot brake and one for the handbrake, the piston size will be appropriate for rear brakes. You might run into uneven pad wear though - that is if you don't do enough handbrake skids to compensate for foot brake use

[YLD-16L]

If handbrakes were truly designed as a means of an effective "emergency brake" they'd operate the front brakes like on some old Subarus etc.

The chances of Joe Public being able to moderate a ratcheting rear handbrake brake in an emergency situation when for the past 20 years they only use the thing to hold the car still when stationary is rarely going to end in a good result.

During pedal operation on a dual circuit system fitted with a hydraulic handbrake if the rear system fails fronts still work, if the fronts fail the rears still work, if the pedal fails the handbrake still works and if the handbrake fails mechanically or hydraulically either the fronts or both still work. If it all fails at once that'd be pretty amazing odds on a well maintained car .

[PeteH]

[QUOTE=1JZ-Rolla]How about a poll, since the mere mention of a hydraulic handbrake must mean that imminent death is near?

Who has experienced (first hand) a hydraulic brake system failure in a well maintained car? QUOTE]

Well +1 from me.

One of the first cars I owned, a HR Holden, came factory fitted with a boosted single circuit hydraulic braking system. Once while driving down a gravel road the RH front flexible brake line was nicked by something and consequently leaked when I applyed the brakes. As this sytem was single circuit losing pressure at any point rendered the entire system useless...i.e one leak means ineffective/no brakes.

On the Ferrari/Aston Martin hydraulic handbrake can somebody actually explain how they work? Are they a single circuit system, or do they have a seperate circuit for each caliper? If they have a seperate circuit for each caliper this may explain why they meet ADR's. As for electric handbrakes do they work in the same fashion as air operated brakes? That is in the event of a loss of air pressure air brakes are applied, so do you need to 'uncharge' something in the system to apply electric brakes?

I believe where the hydraulic handbrake becomes a bit of an issue with an engineering regulatory is when you switch from proven complied OE systems to an aftermarket system that has no ADR compliance.

On the merits of hydraulic over cable operated parking brakes I believe that any reasonable person should be able to tell that their cable operated braking system is faulty when the system can no longer hold the vehicle due to fraying cables or poor adjustment. With a hydraulic system it will either work or not which means average Joe would have to perform preventative maintenance to ensure the system is tip top at all times. The problem with this is that average Joe does not perform preventative maintenance, he will only replace what is broken or worn out. This is the view taken by an engineer when signing off on modified vehicles, not that the vehicle will be owned, maintained and only driven by an above average Joe.

And on the likelihood of catastrophic failure of a cable v hydraulic sytem, who knows? I don't know and I would be most impressed if somebody is able to provide hard facts to support their claims. Just because you have never experienced a failure in either system does not mean it cannot happen.

Maybe the question should be "who has an engineered for road use single circuit hydraulic handbrake system that has also had the mechanical system removed"?

1JZRolla, I apologise for taking your thread further off course but I believe there would be a few members of this forum that could benefit from this debate....me included

Cheers,

Pete

[takai]

[QUOTE=1JZ-Rolla]How about a poll, since the mere mention of a hydraulic handbrake must mean that imminent death is near?

Who has experienced (first hand) a hydraulic brake system failure in a well maintained car? [QUOTE]
Semi +1 from me, ive had a booster blow on a daily, and a complete failure of the brakelines on rally car. Coudl have had something to do with the rock that we hit. Still hard to bring the car to a stop without rolling it.
Oh and the race car had the booster get cooked to a solid lump of rubber inside and hence basically had unboosted brakes.

On the Ferrari/Aston Martin hydraulic handbrake can somebody actually explain how they work? Are they a single circuit system, or do they have a seperate circuit for each caliper? If they have a seperate circuit for each caliper this may explain why they meet ADR's.

The 9 i was under the other day had a setup akin to this one:


This is a setup from a Locost, but works on the same principle. Handbrake actuates a msater cylinder which only works on the smaller sliding single piston caliper. Its held in place normally by a bracket, seen only mocked up here.
The handbrake in this case is completely separate from the main rear brakes.

[YLD-16L]

Re: failures.

I've had two boosters split diaphragms. Brakes obviously still function but with a hard pedal.