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Brake master cylinder types
Mix - 29/5/03 at 12:50 PM

I've decided to construct a floor mounted pedal box and use two master cylinders and a bias bar in the braking system, there are several helpful photos on archive but I can't find a reference to the origin of suitable master cylinders. Thanks in advance
Mick

ChrisW - 29/5/03 at 01:11 PM

Luego sell the two cylinders and the remote reservoir for £100 or so for the set. Looking around at Stoneleigh that seemed to be a fair price. I'll be ordering them on pay day!

Chris

Mark H - 29/5/03 at 01:53 PM

Or Stuart Taylor if they're closer. Either way, I think we've agreed that they are all the same design!

Glenn - 29/5/03 at 02:48 PM

try rally design :

http://www.raldes.co.uk/2003/page023.htm

£24.50 for non-intergral 0.75 master cylinders, this is what you will need.

Ive got to order 3 for myself, brakes and clutch.

BTW its £11.50 for the reservoir's, but im nicking some off some old bikes

Mix - 29/5/03 at 04:11 PM

Many thanks for the quick response, Rally Design looks particularly good value. Any comments ?

Mick

alister667 - 2/9/03 at 10:32 PM

I looking to fit a brake bias bar myself. Any further reports how you got on? Did anyone fit the rallydes cylinders? Did the ST and Luego versions work OK and were they easy to fit?
Thanks in advance.

eddymcclements - 3/9/03 at 09:12 AM

I am using an ST pedal box, and I ordered Girling master cylinders directly from Rally Design as they were the cheapest source. In the end I was sent Wilwood m/cylinders as a substitute, and very nice they are, too.

Pics of pedalbox here and master cylinders here.

Cheers,

Eddy

Browser - 3/9/03 at 11:35 AM

Is there any point having a bias bar unless you are planning to take to the tracks on a regular basis? As far as I can understand, bias adjustable brakes are there to compensate for lightening fuel loads and changing tyre dynamics in racing cars, neither of which will be anywhere near as extreme in a road-oriented 7. I can see the point in a pressure limiter and I intend to use one when I build mine but once set I hope I can leave it alone. Your thoughts/arguments please?

eddymcclements - 3/9/03 at 01:20 PM

Surely a pressure adjuster to the rear brakes is just another way of setting front/rear bias? I am not planning on having a remote adjustment for the bias bar - it's just a way of getting the car set up correctly, then I'll lock it in position. The dual master cylinders in the pedal box also comply with the requirement for dual-circuit brakes.

I realise it's possible to utilise a single master cylinder with two circuits from a donor vehicle, but a. they are virtually all designed for use with a servo and b. I didn't have a donor vehicle!

Cheers,

Eddy

alister667 - 3/9/03 at 04:45 PM

Well it's my hope to take the car to track days a few times a year, and it would be nice to be able to adjust the brakes. I just see the bias bar or valve solutions as different ways to do a similar job. I know the SVA won't let you through if it can be adjust by hand, that got me thinking about using a bias bar and either split pins to hold it or nylock nuts.
Once I get it set it's not something I'm going to fiddle with much, but I imagine as brakes/tyres wear or get changed (say over a course of 3 months between track days) it's ideal position could change a bit, possibly causing 'brown moments' under braking I'd rather avoid ;-)

alister667 - 3/9/03 at 09:15 PM

....mind you, you have got me thinking about this! I suppose if I just used a standard Sierra master cylinder (1 cylinder -> 2 break lines), and mounted a Rally Des adjustable valve (44 quid) that was tucked in out of the way near the diff at the back, it would be as easily adjustable (while not moving), cheaper, SVA compliant and do a similar job......
Hmmmmmm.

Dick Axtell - 4/9/03 at 02:29 PM

quote:
Originally posted by eddymcclements
Surely a pressure adjuster to the rear brakes is just another way of setting front/rear bias?

Eddie & the Rest,
Any brake pressure control valve is used merely to regulate line pressure to the rear brakes. The aim is to ensure that the front brakes will lock up first. This is required by Govt. legislation (EEC Directive 71/320).
Front vs Rear brake balance is governed by the size of the brake assemblies, (i.e. frictional swept area & piston area of hydraulic actuator), and is usually pre-determined at the vehicle design stage.

The binocular mcyl + balance bar is a simple and convenient method for varying the proportion of effort from a single input (brake pedal) between 2 outputs to the 2 mcyls. A combination of the shared effort applied to a mcyl, and its bore area, will determine the associated line pressure.

So all you're balancing is the proportion pedal effort applied to each mcyl.

Now to wait for the arguments.

[Edited on 4/9/03 by Dick Axtell]

alister667 - 4/9/03 at 09:47 PM

quote:

Any brake pressure control valve is used merely to regulate line pressure to the rear brakes


Does that include an adjustable proportioning valve? Surely it can be used to proportion the rear brakes? Same as the one in the Rallydes catalogue http://www.raldes.co.uk/2003/page023.htm
(down near the bottom, "Knob Style Proportioning valve".
As I understand it a valve like that could never be used to increase the rear brake balance, but if your original design was set up so rear brakes were slightly stronger with the valve open, using a valve to reduce the effectivness of the back brakes would allow you to balance the front and rear effectively?
...mind you I haven't even started my build yet, and I've only just started thinking about brakes in the last couple of days :-) I could be talking rubbish!

Rorty - 5/9/03 at 02:31 AM

alister667:

quote:

As I understand it a valve like that could never be used to increase the rear brake balance, but if your original design was set up so rear brakes were slightly stronger with the valve open, using a valve to reduce the effectivness of the back brakes would allow you to balance the front and rear effectively?
You'll probably find the brakes seem more powerful in the Locost than in the donor, simply because of the lesser weight of the Locost. Therefore, the rear brakes can quite easilly over-power the fronts.
The balance adjuster, whether hydraulic or mechanical will allow the rear pressure to be backed off, so the front brakes definitely lock first.
Incidently, if, for some weird reason you did want more line pressure to the rear than the front, the mechanical adjuster would obviously cater for this. The hydraulic bias valve could be installed in the front brake circuit for the same result.

Mix - 5/9/03 at 07:31 AM

Dick

I have been looking for the formula to work out braking effect and have asked the question here before. The best response I received, (it may have been from you) was very complex so if I were to rephrase the question and ask for a formula which would give me a good approximation, (disregarding the effects of suspension), could you enlighten me, or would this be meaningless??

(All goes back to trying to work out what size master cylinders to use).

Mick

Dick Axtell - 5/9/03 at 01:37 PM

Hi Mick,

I'll try and blag some info from (former) work, 'cos that'll be the kosher version.

LoL
Dick

eddymcclements - 5/9/03 at 03:34 PM

quote:
Originally posted by Dick Axtell
Any brake pressure control valve is used merely to regulate line pressure to the rear brakes. The aim is to ensure that the front brakes will lock up first. This is required by Govt. legislation (EEC Directive 71/320).


OK so far.

quote:
Originally posted by Dick Axtell
Front vs Rear brake balance is governed by the size of the brake assemblies, (i.e. frictional swept area & piston area of hydraulic actuator), and is usually pre-determined at the vehicle design stage.


So far so good.


quote:
Originally posted by Dick AxtellThe binocular mcyl + balance bar is a simple and convenient method for varying the proportion of effort from a single input (brake pedal) between 2 outputs to the 2 mcyls. A combination of the shared effort applied to a mcyl, and its bore area, will determine the associated line pressure.


Absolutely agree with you. I need more pressure in the front brake lines, so I have a .625" front master cylinder and a .75" rear master cylinder. Together with the bias bar I think I'll be able to find a point at which front/rear bias is correct (erring on the side of caution) and will lock the adjuster at that stage.

All I was pointing out was that a rear brake line limiter achieves the same end result - ie. removes the possibility of rear brakes locking before the fronts - of course the way in which this is achieved with the two setups is different.

quote:
Originally posted by Dick Axtell
Now to wait for the arguments.


Not from me!

Stu16v - 5/9/03 at 06:07 PM

Yup, if you have means of altering the front/rear bias, whether it be mechancial or hydraulic, what is there to argue about?

quote:

Any brake pressure control valve is used merely to regulate line pressure to the rear brakes. The aim is to ensure that the front brakes will lock up first. This is required by Govt. legislation (EEC Directive 71/320).


Can I assume that you also include inertia valves and load sensing valves in this statement Dick?

[Edited on 5/9/03 by Stu16v]

mad4x4 - 6/9/03 at 04:03 PM

quote:
Originally posted by alister667
I looking to fit a brake bias bar myself. Any further reports how you got on? Did anyone fit the rallydes cylinders? Did the ST and Luego versions work OK and were they easy to fit?
Thanks in advance.


To throw another option in I used Landrover IIA masters they are girling 1" needing 7/16" nipples. If one can stop a 3.5 ton Landrover 2 with bias bar will stop a kit car.

Cylinders from Paddock's @ £16.00 each <
Balance bar from Raceparts UK @ 34.52
7/16" Nipples from Think Automotive Ltd 27p Each

Stu16v - 6/9/03 at 08:23 PM

IMHO I reckon two 1" cylinders would be too 'overgeared' for most Locost applications, requiring a lot of pedal effort to stop the car.

My car has two 0.625 cyls fitted, and I have little pedal travel and a 'firm' pedal.

The one Landy cylinder was running the complete brake system on it's orignal donor IIRC....

Rorty - 9/9/03 at 05:58 AM

Stu16v:

quote:

IMHO I reckon two 1" cylinders would be too 'overgeared' for most Locost applications....
Not if he has longer pedals.
Basically, if you're pedal is too firm; fit smaller diameter master cyl or longer pedal. Vica versa for the opposite.
If altering the length of the pedal, don't forget to raise/lower the pedal's pivot point to keep the pedal pad the correct height off the floor.

Dick Axtell - 9/9/03 at 07:57 PM

quote:
Originally posted by Stu16v
Can I assume that you also include inertia valves and load sensing valves in this statement Dick?


Yes. But beware inertia, or so-called 'G' valves. Their performance can be too variable.

Stu16v - 9/9/03 at 10:09 PM

quote:

If altering the length of the pedal, don't forget to raise/lower the pedal's pivot point to keep the pedal pad the correct height off the floor.


Accepted mate, but hence my comment.....most folk building locosts have floor mounted pedals when using dual M/Cs', and it just so happens that more often than not, the pedal pivot is already on the floor....

There may be scope to lessen the distance between the pedal pivot and the bias bar mount, but I personally dont think there will be enough to get a nice feel with 1" cyls IMHO.
Of course, with top mounted pedals there isnt an issue......