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Brake Set Up Advice


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Could someone give me some advice about my brake set up.

I am slowly finishing my project and have fitted disc brakes from a Sierra front and back but am concerned when test time comes around the front braking pressure will be the same as the rear and this would be wrong.

With modern cars I know that the rear braking balance is set up 60/40 so do I have to do the same or different .

I have fitted the brake system as provided in the kit but have yet to add brake fluid and bleed the brakes.so do I need to fit some kind of brake bias element and where and what do I have to get.

Hope you can help a bit of a novice.

This project had been over the last 3-4 years and I have lost a bit of focus on it

Thanks

Chris D

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First of all let me say congratulations on sticking with your build.

On completion you will be so chuffed that you will see all the effort and expense has been well worthwhile.

Ask anyone that has built their own and had it tested.

 

The kit suppliers should know what they supplied works, so I think a valve would be with the kit if required.

 

There should be some difference in the front and rear calipers to do this job for you.

 

To eas your mind you can get a brake roller test at any garage that does mot testing.

This would give you an idea of what needs doing, if anything at all.

 

Good luck with your build and you have many happy and proud days to come.

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Hi Chris, it will all be worth it in the end! The longer the wait, the sweeter the reward.

 

What master cylinder are you using? Assuming the Sierra one and standard Sierra rear discs you may find it is ok without any extra pressure adjuster. If you are using twin master cylinders you will need a bias bar.

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I got my master cylinder from GBS so not sure of the origin but it has a 2 feeds to the front and a single feed to the rear. It then has a splitter at the rear to go to the 2 sides. So the way I look at this is that the front is getting 2/3rd and the rear 1/3rd of the pressure. It went through IVA on this basis as has been more than adequate on the road in normal use.

 

I am sure someone can explain it better than this, but if you have the same set up, it will be fine.

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Sounds like the normal sierra master cylinder.

The 2 outlets to the front are in place of a T so the same pressure all round.

This master cylinder internally is in 2 parts so that a single hydraulic leek still leaves you with some brakes, either both front OR both back.

The split in braking force is given by the relative piston area in the calipers / wheel slave cylinders. Normally the front are significantly larger.

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You should stop worrying at this stage if you can assume that the brake components are matched and all came from the same sierra or same spec sierra, then ford have done the thinking for you. They chose the relative sizes of the master cylinder(s. Two in tandem/series) and the size of the discs/pads/calipers on front and on the rear of the original car during the design process with the intention of producing the safe bias of braking, front to rear.

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DavidS your assumption is wrong

There are 2 Pistons in the master cylinder feeding a split system front and rear you are moving the same volume of fluid for each system front/rear

The 2 outlets at the front effectively split at the master cylinder

The 1 at the rear splits at the T piece

Therefore front and rear get the same volume

It starts to change the braking effect at the calipers and or drum slave cylinder

Not as simple as 1/3 2/3

The Sierra has a brake pressure relief valve for rear discs as even on the heavier car the rears can lock early as the weight transfers forward

We have got disc braked cars through IVA (just) drum brakes with ease

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Post #8 explains it correctly.

Pressure relief valves are actually load sensing valves.

The valve is,fitted to the chassis rear and the operating arm is fitted to the axle. Or can be done the other way around.

As load is added to the cat, the body goes down pushing the arm upwards opening the valve to allow more pressure.

Probably easy to get one and easy to fit.

Very difficult to set. They are pre set on cars by the length of the arm with all sierra's being built standard sizes, so the rods are made the same length.

Kit cars do not come with the same chassis to axle specs so have to be set separately.

Very difficult to do indeed.

Using a pressure,guage. How,do you know all the air is out of the hydraulics after fitting the guage.

How do you know ho long to make the operating arm, then keep modifying it until the pressure is correct.

It can be done with an adjustable length of rod, then when set correctly remove and measure the rod, making a none adjustable one to the exact same length.

This must all be done with someone in the driving seat, just as there will be during the IVA brake test.

 

For what it is worth, as longboarder states. Don't worry about that at this point. The caliper piston, disc and pad sizes do most of the compensating for you. The load sensing valve is to automatically give more pressure as required by a loaded car, especially estate cars.

These were only fitted to cars as things got a little more sophisticated, and are not to this date legally necessary.

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The sierra i used has a canister in the rear brake line that is set at an angle. when the car stops hard a ball bearing rolls forward and shuts off some of the rear pressure. i just set mine to a slightly shallower angle as the seven won't dip as much as a seirra. this is much simpler than the lever setup running off the suspension etc.

 

passed sva in 2007 without issue.

 

vented fronts/drums rear

 

hth

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