International Lancia Forums

17 days have passed since the last Fulvia posting. Has no-one anything to ask?

I'll take the opportunity to say that I am working in France - that is I have been working in France and will be back in about three weeks or so. I am working in Haut Savoie and would be very happy to see any Fulvisiti who care to contact me.

Best to everyone

Paul

Hi Paul,

maybe i have a point where you can help.

I have reworked the brakesystem of my 1,2 first series coupe.

I reworked the wheelbrake zylinder with sleeves and new seals and brakepads.I use a reworked masterzylinder from the second serie with dia. 21 to have more brakeforce.
In general the mech. of the hyd.System works ( no oil leakage and no air in the zylinder´s).

But and this is the point the brake force is more ore less 0.I would like to say the rear handbrake
is better than the hydr.system.

It´s absolutely strange.

Maybe you have an idea what´s going on

regards

Andreas

Although you asked the question to Paul, allow me to answer it.

The calculations are similar to the calculations for levers as first published by Archimede over 2000 years ago. If you have a lever which is on one side 1 meter and on the other side 2 meters and place 1 kg on the tip of the 1 meter arm, you can lift the 1 kg by pushing with a force of 0,5 kg on the 2 meter arm. The penalty is that the distance over which the 2 meter arm is moved is twice as long.

Every time I see a system where one can trade force for distance of travel I picture Archimede in my mind. I must admit that I do not see him operating levers but see him jumping out of the bath shouting "Eureka".

If you want to push a Fulvia (or any other car) slightly uphill the trick is to not push the car body but the top of one of the wheels. The wheel functions as a lever. The distance of travel of the top of the wheel is twice as long thus in turn the force on the body is twice as high compared to just pushing the body itself.

In hydraulic brake systems one has to displace an amount of liquid with a certain force. The amount of liquid to be displaced depends on the surface area's of the wheel brake cylinders and the required distance of movement.

If you reduce the surface area of a pump by 50% it means the distance of travel is twice as long but you are rewarded by having to use only half the force or said differently with the same force of your foot you can apply twice the force to the pads.

The Flavia has the same brake system as the Fulvia but uses a 25mm pump and has a servo. On the Fulvia the servo was dropped and the surface area of the pump reduced to 18mm. The 18mm is roughly (half the square root of 2) times 25, thus the surface area of the 18mm pump is half that of the 25mm pump. With the same pedal force one doubles the hydraulic pressure and thus doubles the force on the pads at the price of a distance of movement which is also doubled.

A considerable amount of pressure and liquid is needed to inflate the rubber hoses. The inside diameter increases quite a bit. Just put your hand around one and let someone pump the pedal. I have never done exact measurements but I guess that on old and / or bad quality hoses there is more fluid and effort needed to inflate the hoses than to move the pistons. On the series two there are 5 hoses versus the 3 hoses on the series 1. This made it necessary to increase the diameter of the pump to displace enough fluid to inflate the hoses and still have a safety margin to compensate for air in the system and other mishaps. Increasing the diameter of the pump made it also necessary to install a servo.
Note that the combined surface area of the small and the large piston in the S2 Girling calliper is exactly the same as the surface area of the S1 Dunlop 2 1/8” cylinder. Also the surface area of the piston in the rear calliper is very close to the surface area of the Dunlop rear cylinder.

If you compare the brake systems of the various Lancia's you will notice that the servo is never used only to have more brake force with less pedal force. It is always a combination of reducing pedal force and reducing distance of travel. The latter translates into a “harder pedal”.

I now mount the reinforced Goodridge hoses on the series 1. They hardly change diameter. The difference is enormous. I would never change the Dunlop brake system with the 18mm pump and the Goodridge hoses for any other brake system. It is very direct and very effective. I also perforate the discs which helps to keep the friction material of the pads open and which breaks any layer of water on the discs.

The movement of the pistons depends on the retraction of the pistons after the previous braking. The technical book specifies that the retraction should be between 0,05 and 0,13mm for the Dunlop brakes. The retraction is determined by the retraction mechanism in the piston and the axial play of the pin in the cylinder.

You can check the retraction by looking at the pistons and pads while someone else pumps the pedal. The travel of 0,05 mm cannot be seen but you can feel it. If you clearly see the pistons move it is too much.

When I overhaul Dunlop brakes I also overhaul the pistons. In fact I machine new pistons using specially made tools to make sure the retraction is set at 0,05mm.

Note that the combined surface unevenness of the discs and the pads should be well under that 0,05mm to have maximum efficiency.

I do not sleeve the cylinders. Although simple calculations show the bushes are safe I do not trust it. The cylinders are subject to extreme thermal cycling and also thermal shock. If the brakes are very hot and one drives through water, the thermal shock is very high. I have not been able to translate the effects of thermal cycling and thermal shock combined with peak pressure in case of an emergency braking action into calculations. If one places bushes the original cylinder wall has to be machined and thus reduced in thickness. The size of 2 1/8” is increased. There used to be a 2 ¼” wheel brake cylinder in the sixties but is was quickly dropped as they broke often.

I grind the cylinders to 0,5 oversize and make the new pistons also to 0,5 oversize. The cylinders are then nickel plated using an electroless process followed by a galvanic zinc layer.

The maximum temperature of the wheel brake cylinders is determined by the boiling point of the brake fluid. This is about 200 degree C for DOT4. When the fluid starts to boil, braking ceases and the temperature does not increase further.
The pistons are solid and expand over temperature. The coefficient of thermal expansion of the original material for the front pistons is about 12*10-6 mm/mm. At 200 degrees C they are 0,12mm larger in diameter compared to room temperature. I have verified this by actual measurements.
The cylinders do NOT expand over the larger part of the cylinder. The ratio of wall thickness and diameter is such that the wall expands itself inward and outward. This expansion is practically nil because the wall is very thin. Near the bottom however the cylinder does expand because the bottom is solid. Bushes will not expand near the bottom as they consist only out of a thin wall.

Note that it is dangerous to use fluids with a higher boiling point than about 200 degree C in the Dunlop brakes. The pistons may seize. On the Girling brakes it is probably safe as the pistons may not expand due to the ratio between wall thickness and diameter. If have never done measurements on the Girling pistons, but I figure the reason for being hollow is to eliminate thermal expansion.

I also figure that you know all the above. So why did you change the diameter of the pump from 18 to 22mm?

Also note that because of the super Duplex Girling system the volumes of liquid to be displaced by the chambers in the pump are different from the Dunlop brakes. Did you test the brake system with the front circuit inoperative and also with the rear circuit inoperative?

Hi Huib,

the most of your explaination forsure is clear.And foresure your wellcome with your
experience.
Onother effect is that we have some postings here.

Comming to the question why i am using the second series masterzylinder.

After the rework i have at first use the 18 mm master zylinder ( in good condition) with the
instalt brake assistant.( was in this car )
All the 3 hoses are new,too and also the tubes on the "brakeblock" themself.

The result was as bad as know.

After that i eliminate the brake assistent because i supposed that the brake assistent wasn´t
ok.
The result was as bad as know.

Then i try to compensate that with the second serie masterzylinder ( 21mm) to have with the same
force on the brakepedal ( that means what i am able to do with my feet ) any result.
Seems to be stupid if i see the result.

But in this situation i made a mistake.The space between the piston of the masterzylinder and the padelbolt wasn´t correkt and the brake workes for a short time well, but after this with the upcomming temperatur the brake closed more and more.( normal with this mistake ) but it showes in general it work´s..
I correct this space then and you know what´s comming now:

The result was as bad as know.

I have done everything step by step and it seem´s that i made another mistake, but i don´t know
what kind of.
It is a strange thing in my opinion

regards and a nice day

Andreas


PS. The bakesytem on my secondserie zagato works perfect so in general i suppose that
i should able to do a job like this.But ...

Sometimes it is tough.
Let's define "reparation"as an action to correct a problem and "restauration" as bringing the car or subsytem in the same condition as when the car was new. I must admit that I cannot always resist the temptation to make it "better than new" which does occasionally backfire.

For most if not all of the S1 cars it is time for a complete restauration if not already done. It is best to leave no loose ends. Thus mount new discs or at least properly skimmed discs, new lines, new hoses, new masterbrake cylinder, new or correctly overhauled wheel brake cylinders, de-rusted and zinc plated callipers and the proper pads. I don't think twice about mounting a new master brake cylinder. After all those years of use, abuse and no-use these cannot be anything else than bad. If you assemble a brand new aluminium master brake cylinder, fill it up with brake fluid and put it under your bed, it will be bad after 30 years. Acids from the rubbers will have changed the structure of the aluminium. And there is a whole range of other chemical and physical reactions.

The actual braking happens where the pads are in intimate contact with the discs. This is where it occurs. The rest is remote control.

The pads are important. I refuse to use any other pads than those from Mintex. I still have some of the old M69FF pads (with vitamin A) which are best, but the new Mintex pads without vitamin A come very close.

Is there any way of establishing whether the problem is between discs and pads or in the "remote control"?

Andreas,

I am not quite clear about your message, but I would ssay that since the overall piston area of the wheel cylinders is the same as the, if you have not got a servo (you don't mention this} you will have to apply enormous pedal effort to get good braking.

Paul

To add to Huib's excellent message, on my Fulvia (SI rear brakes) the cylinders (1 5/16") were lined with stainless steel 10 years ago, have given no trouble and are working perfectly. I agree of course that the front cylinders are marginal.

As for master cylinders, at the late-lamented Evolution Engineering, we used to line these with stainless steel with great success, but it was not a cheap operation.

I gave up on my 18mm cylinder and now use a 19mm one from a FIAT Regata. I had to make an adapter plate and a longer push rod, but it is a total success.

best of luck

Paul

Thanks Huib,

i believe that the pats could be the point.This is what i am not thinking about.

The pads are foresure also new, the masterzylinder ( 18 mm ) was more or less new ( 1,5 years old with the bill from the last owner ), and the used 21 mm second series i had overhauled as on my Zagato.

So there is no reason why it should not work with all this parts.
Maybe the brake was the reason why he sold the car.
But i will kill this pig of brake and i am sure that i win. )))

The only thing i have to check now is, as you said, the pads.

I will contact you for this.

best regards

Andreas

Hi Paul,

this is also one of the points.

I didn´t drove in the past a 1.Serie´s car with this dunlop brake.And so I haven´t a reference
what pedalforce i have to have for a good braking effect.

I have only the secondseries and this is a big different.

thanks also to you

Andreas

PS.:

I try it with and without the servo.

I have an enormous stock of the new Mintex pads. Let me know what you need.

Also the discs have to be clean and flat.

Callipers properly centered using shim rings. Pistons exactly perpendicular to the discs.

What often happens is wrong orientation of the seal on the rear of the plunger for the rear wheels. If it is not an O ring but a seal it has to face to the front wheel chamber as it receives presure from there.