Pedal Box & Brakes

One of the many things that I hadn’t thought of, or should I say realised, was that by fitting twin Webers, which are on the off side of the engine,  I blocked where the Sierra pedal box should go. 

So next obstacle was to source a floor mounted pedal box.  Eventually found one on Ebay,  we had to make a mounting for the pedal box, so out with the mig welder and we fabricated a frame to hold it in place.

                 

 We then bolted the frame to the chassis and then secured the pedal box to the frame, job done.

You may notice the foot rest to the left of the clutch pedal, we cut out a section of the tunnel panel and fixed in a small box section into the side wall, giving us a handy rest for your left foot, very welcome on those long runs.

 

Because the car will have a very light rear end it is advisable to fit the Sierra Pressure Reducing or Deceleration Valve (PLV) in the rear brake circuit. This is to help prevent the rear brakes locking up during moderate or heavy braking, however the only way to adjust the Sierra unit is a bit hit and miss, you need to adjust its angle relative to the road, not easy once it is fitted. I opted for an adjustable brake proportioning valve from Rally Design, this is fitted in the rear brake line to the side of the transmission tunnel so can be adjusted from the drivers seat and balance the brakes to give the best braking without locking up the back brakes.

 

                                     

 

After fitting the valve it was brought to my attention by a fellow Hoodie that the IVA are not keen on the brakes being adjusted once they have been set and passed through the IVA, the solution is to balance them and once you are happy with the setting remove the knurled knob so they can’t be adjusted again.

 

STOP PRESS MARCH 2010: I visited my local VOSA Centre and spoke with the nice examiner man, you must NOT fit an adjustable brake bias valve, even if you adjust the balance then lock it off, it will fail the IVA, when asked how am I supposed to balance the brakes, the answer “By design”  !!! BE WARNED

 

I have now removed the adjuster, you will see it on ebay very soon.

 

                       

 It wasn’t until later that we realised that by putting the brake master cylinder down at floor level we were going to have major problems when we went for our SVA.  This states that ‘On all fluid reservoirs, the filling ports are readily accessible to top up the fluid’,  Ours was far from accessible.  After much deliberation we bought a combination remote tandem master cylinder which allowed us to fit the reservoir on the scuttle and so have easy access for filling.  

                         

 This was purchased from Rally Design in Faversham, a very helpful crew. 

Trouble is that was not the end of it, with the master cylinder mounted so low, it was lower than the disc brake calipers, this resulted in some fluid flowback to the master cylinder reservoir, thus creating a vacuum effect that retracts the caliper pistons into the housing. This caused the pedal to go to the floor on the first stroke until it has ‘pumped up’ and has moved all the pistons out against the pad again, no amount of bleeding will correct this. The answer is to fit an in-line two pound residual pressure valve in the front and rear systems, installed near the master cylinder. As you can see from this picture.

 

                       

 

This corrected that problem but I wasn’t happy with the slight flexing that I got from the master cylinder when I pumped the pedal, having a fixed copper pipe to the master cylinder worried me that it may fail the IVA, see picture above this one. Solution was to replace the copper pipe with stainless steel braided hose and banjo fittings.

Also along the same lines I had a comment from a fellow Hoodie when he called in to pick up a fuel tank sender that I had spare. Whilst proudly showing off my build, and fishing for compliments, he pointed out that a friend of his had failed the SVA where the front solid brake pipe goes through the side panel and connects to the flexible hose feeding the front calipers. The solution is to fit a securing bracket to the inside of the panel to stop the stainless steel panel flexing, see picture,   

                                                                  

          

Worth pointing out at this stage, if you are using flexible brake hoses then be careful because not all pipes are SVA complient, in section 16.4 of the SVA manual  it states ” Compression joints of the type using seperate ferrules are not considered suitable for joints on hydraulic brake lines other than in the case of a hose designed for a high pressure application that incorporates an inner support sleeve in the compression fitting”
Basically what this means is that the pipe should have a sleeve inside the inner bore to support it, see picture;  
                       
                     

This stops the ferrule squashing the pipe and restricting the flow of the brake fluid. I am fortunate that I only live 10 minutes from the VOSA Centre in Gillingham and I called in and spoke to one of the inspectors who was very helpful, he advised me to take a picture of the fitting, as above and bring it along on the day of the test to prove that I had used the correct fittings, the alternative is to disconnect it to show the inspector and end up losing your brakes!! Not really an option.
Back to the master cylinder, you would have thought that this would have been brakes done, no such luck, with the pivot of the pedal so low down we got far too much travel in the pedal, solution is to move the master cylinder up and make the pivot point higher thus reducing the pedal travel, this job is currently underway, watch this space.
As you can see from the above picture, I have repositioned the master cylinder higher up the pedal which reduces the pedal travel, exactly what I wanted to do, however as it was trial and error I think the pedal may not now have enough travel !!!! Before I change anything else I will run the car and get the pads to bed in and see how it feels.
Latest update, still not happy, now we do not have enough pedal travel, apparently there is a formula that you use when deciding which brake master cylinder you should use. The way you calculate the size of the master cylinder, ( piston diameter )  is by calculating pedal ratio, pedal travel and caliper piston diameter, I did none of this, hence my problems. By increasing the pedal length I increased the leverage but you then get less fluid movement, if the pedal length is 12″ long from the fulcrum to the foot pad and the cylinder push rod is 3″ from the fulcrum then the pedal has a 3 to 1 ratio, confused ? I am so we took off the Wilwood master cylinder and refitted the Westfield master cylinder with a remote reservoir and fluid reservoir cap. Tried the brakes and much much better, we did go all around the houses, not literally, to end up where we started, but hopefully this has now corrected the brake problem.

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