master brake cylinder

[Tinman]

ordered my new master brake cylinder today, however i was about 2o minutes late so now i have to wait till Monday morning.
now just the cv joint left, then its all done and running smooth (touch wood).
i was surprised just how easy it was to take the old master cylinder off, usually everything takes a hammer to get off :)

[Tinman]

new master brake cylinder installed and wow huge difference
its nice to be able to be able to stop going down hill :)

[Scooter]

Glad you are up and stopping Stuart.

Do you reckon you get more pressure with the new master cylinder?

[CasKru]

Glad you are up and stopping Stuart.

Do you reckon you get more pressure with the new master cylinder?

Was wondering the same thing because at Rust De Winter I was basically standing on the brakes going down one hill but did not stop :problem:

[Tinman]

yes a huge increase in preasure,
now it pulls up relativly quick going down hill even when doing 80km/h plus
and being a brand new unit i know im not going to have any problems for a few years.
i also renewed all brake pads, with top quality ones.
over all a good bit of money spent and it did solve the problem :)

[Mr_B]

This is on my to-do list... since I fitted 33's I have found the brakes inadequate, actually they weren't great even before that... I have heard a decent brake upgrade is to fit landcruiser calipers and discs in front... I'm first going to get a new/recond master cylinder though!

B

[Tinman]

id prefer to fit disks on the rear rather than modify the front ones

[Toybox]

Well I can confirm that the vented front discs make a huge difference. I use croozer discs with IFS callipers and a smaller master cylinder.

The swop is very easy to do without any mods necessary; just swop the old stuff out with the new goodies. The only mission is getting the discs themselves out, repacking wheel bearings and all that jazz.

If you're planning it then you might as well replace the half shaft seal at the same time.

[Big D]

Toybox, why did u use a smaller master cylinder?

My brakes are shot, and need to replace them, but want to upgrade,

What IFS callipers did you use?

[Toybox]

The smaller master theory took me a while to wrap my head around but as far as I understand it, it goes a bit like this:

Larger = Stiffer peddle with less travel but less line pressure for the same peddle effort (i.e. It take more leg effort to generate the same brake torque at the wheels).

Smaller = Softer peddle with more travel but more line pressure for the same peddle effort (i.e. it will take less effort to generate the same brake torque at the wheels but well require longer peddle stroke).

I used Croozer 60 series discs (I could be a bit wrong here, it's been a while) and 2.7 callipers. As far as I know there are a couple variations of these callipers, with some differences in piston size. I'm not entirely sure which ones I have, but both the pistons are the same size. Any variation should work.

You can use your existing callipers if you split them and add an 8mm spacer between the two halves.

Also remember that you will need to use a wheel spacer otherwise the rim will knock against the callipers....

[CasKru]

Mechanical advantage - why you can stop a 2-ton car with one foot.

If you did any sort of physics classes when you were back in school, you might remember something called mechanical advantage. In its most basic form, mechanical advantage is the ratio of force-in to force-out in a mechanical system. Mechanical Advantage = Effort Torque/Load Torque.
For example a 20kg weight 1 metre from a pivot can lift a 40kg weight 0.5m from the pivot on the other side. The effort torque and load torque calculations are to do with force in Newtons and distance from pivot point. Hence torque is measured in Newton-metres, or Nm. A Newton is the amount of force required to accelerate a mass of one kilogram by one metre per second². On Earth, where acceleration due to gravity is 9.8m/s², the force exerted upon a mass of 1kg is 9.8N (usually rounded up to 10N). Another popular notation is lbf.ft - pound-force-feet, commonly referred to as foot-pounds. 1 Newton-metre is equivalent to 0.737 foot-pounds.
The diagram below shows a simple lever system on a pivot. The load torque is 200Nm, and the effort torque is also 200Nm. Mechanical advantage = effort / load, which in this case is 200 / 200, which is 1. ie. the system is balanced.

basiclever.gif (5.3 KiB) Viewed 2356 times

Now imagine increasing the weight on the effort side to 30kg instead of 20kg, but leaving everything else the same. The load torque is still 200Nm, but the effort torque is now 300Nm. Mechanical advantage = effort / load, which is 300 / 200, which is 1.5. Any mechanical advantage value larger than 1.0 means that the effort has the advantage. In this case, a 30kg weight which is lighter than the 40kg load, is able to lift it off the ground.

basiclever2.gif (5.19 KiB) Viewed 2356 times

If you now take your new-found / remembered knowledge about physics and look at the simple lever brake system, you'll realise how it's possible to generate enough force using your foot to stop a car or motorbike. Look at this diagram of the lever-operated cam brake.

complexlever.gif (5 KiB) Viewed 2356 times

This system has 4 levers in it. The middle two have no mechanical advantage as the levers are connected the same distance from the pivot in each case. However, look at the pedal. The values I've put in are arbitrary but they serve the purpose. On the pedal we have some amount of force 20cm from the pivot, but the other end of the lever is only 5cm from the pivot. This gives us a mechanical advantage of 4 on the brake lever (20cm / 5cm).
At the other end, the lever attached to the cam is still a lever system - it's just bent. The input lever is 10cm long but the cam is only 4cm across - or 2cm to the tip from the pivot. So at the brake cam we have a mechanical advantage of 5. (10cm / 2cm). So across this entire system, we have a total mechanical advantage of 20 - 4 from the brake pedal and 5 from the lever and cam. Apply force to this little system and be amazed. The units of force used are irrelevant - they're multiplied just the same. To use easier-to-comprehend values, let's imagine that when you're braking, your foot is pushing on the brake pedal with about 60pounds of force - 27Kg. Through the brake pedal, that is amplified 4 times to 240pounds, and through the lever and cam its amplified a further 5 times from 240pounds to 1200pounds. You pushed the pedal with 60pounds of force, but the cam inside the drum brake is being forced out against the brake drum with 1200pounds of force - about 544Kg. Sweet.
Mechanical advantage as applied to hydraulics.

pressureexample.jpg (3.99 KiB) Viewed 2356 times

Most braking systems now use hydraulics. This is a slight change in the equation but the concept of mechanical advantage still exists, this time by the use of pressure equations. Pressure = force / area. If you apply 20 Newtons of pressure to 1m², it's the same as applying 200 Newtons to 10m². Why? Because 20 Newtons of force divided by 1m² of area generates 20 Pascals of pressure. Similarly, 200N / 10m² is also 20Pa.

If you now think of that in terms of a hydraulic braking system, it becomes clear how mechanical advantage works for you. Brake fluid is incompressible - it has to be. This is good because it makes calculation for hydraulic brake systems quite easy - you can eliminate the internal pressure from the equation.
Split the system into two parts - input and output - the brake pedal and the brake caliper piston.
For each part, Pressure = Force / Area. The Pressure is the same at all points in the system, so some basic algebra gives a simple formula:

hydraulicforces.gif (11.89 KiB) Viewed 2356 times

Using our previous example, we apply 60pounds (27Kg) of input force to the brake pedal. This is attached to a master piston which (for example) is 1.25cm across - ie. it has a surface area of 0.000491m² (remember your maths? area = PI x r²). At the other end of the system is the caliper piston, which for example is 2cm across - ie. it has a surface area of 0.001257m². Using our sparkly new formula, the output force from the caliper piston is
60 x (0.001257m² / 0.000491m²) Get your calculator out and that comes out to 154pounds (69.8Kg) - more than double the force at the brake pedal. The ratio of output area to input area is sometimes referred to as the area differential.

So that, my friend, is why you can stop a speeding vehicle with a single foot.

[Family_Dog]

The diagram below shows a simple lever system on a pivot.

I ain't bin seeing no diagram, Cassie?


-F_D

[Mud Dog]

I see you also have your moments, Cassie!

[CasKru]

The diagram below shows a simple lever system on a pivot.

I ain't bin seeing no diagram, Cassie?


-F_D

Seems the link is broken

[CasKru]

sorted