Works style rally car preperation for the clubman budget

The Braking System

     As previously mentioned the brakes were renewed all round in so far as we had fitted new disc's and pads and overhauled the calipers, but the other thing we wanted to do which wouldn't cost the earth was to move the solid pipes inside the car to protect from rocks and stones and replace the rubber pipes at each corner with steel braided items which improve pedal feel. First up was to move the copper brake pipes inside the car. This is usually done to help plumbing in a hydraulic handbrake and a bias valve, as both these items will be placed in the car within reach of the driver and to tee these in to the existing pipes running under the car would prove a major pain.
Before we started making up pipes we had to fit all the items to be plumbed up. The handbrake required a little taught before it could be fitted, the transmission tunnel was kinda crowded already with the gear leaver where it was and we wanted  to have a verticle handbrake lever for easier use in the quarrys. The problem was where we could get room to bolt the brake cylinder on top of the tunnel the lever coming out of it wasn't in a comfortable position and made it ackward to use the gearleaver, so what we decided on was to fit the cylinder in the same position and move the lever forward to a comfortable position and have a link bar connect the two as shown below.


      The lever is now in a comfortable position and doesn't get in the way of the gearchange. Also shown above is an adjustable brake bias valve, mounted beside the handbrake cylinder,  you can just see the little red lever attached to it.
       The plumbing of pipes could now commence. Two pipes were taken from the front master cylinder, the front pipe was split in two by the use of a handy little tee piece found in a jeep at the scrap yard and from here one pipe was routed forward to supply the front calipers and the other plumbed through the car and then out to the rear calipers. the other item that needed fitting to the rear brake line was a bias valve. The reason for this I will try to explain with the use of another fantasticaly detailed diagram.

         Now as is usuall when it comes to looking at one of my diagrams you are going to have to use a fair deal of imagination to try and make sence of it all. In the "masterpeice" above you can see the inside of the mastercylinder is split into two chambers  (not strictly true in real life but it's easier for me to get my head around). The front chamber supplys fluid to one front and one rear caliper, usually arcoss the diagnals (ie. front left and rear right)  and the rear chamber supplies the other two calipers. Both chambers in the mastercylinder are the same size so when the fluid is compressed equal amounts of fluid are sent down each pipe which normally results in a nice balanced brake applied. With our car we have taken the feed from the front chamber and used it to supply the front two calipers and the feed from the rear chamber is used to feed the rear calipers, which means we only have to run one brake line through the car from the mastercylinder to the rear before spliting it out to both rear calipers. The benifits of this are when you are plumbing up the hydraulic handbrake you only have to tee into one brake line. But plumbing this way also can throw up a problem. Both chambers in the mastercylinder are the same size and as such when pressurised when the brake pedal is pressed they push out the same amount of fluid. In the standard system this isn't a problem as each brake line has one small and one large caliper to fill which keeps things nice and even front to rear, but in our way the size of the two rear chambers connected up to one line are much smaller than the two fronts connected to the other. The result? The rear brakes lock up long before the fronts are doing much braking at all. Very entertaining to watch from the outside but not so funny from the drivers seat. The solution? Fit a brake bias valve on the rear brake line which limits the amount of pressure reaching the rear calipers. This valve is adjustable so you can vary the amount of braking the rear does compared to the front and in theory set the braking system up as you please. We have set up our so that at full braking the rears lockup just before the fronts and the back of the car slides making it easier to get it turned into tight corners. Sounds real professional doesn't it, what usually happens is we leave the braking far to late and end up wipeing out most of the barriers, oh well they say practice makes perfect
          With the braking system now fitted all that remained to do was fill the system with fluid and bleed out any air. There is a huge range of racing brake fluid out there with prices that vary with brand name. You can spend a fortune and fill up with fluid that would brake a tank driving down a cliff face without ever boiling but you will never use it that hard in your car. We use a synthetic fluid from a crowd called Bardall, which sells for 18euro a litre and so far it has given no problems, if it does we'll upgrade but till then we've better things to spend the tiny budget on!

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