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Thread: Better brakes - Final Opportunity

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  1. #11 Dual 7" Servo : Better Brakes 
    frequent forum contributor Club Member Mike's Avatar
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    Hi Mike (mike&jeansy.org)

    Thank you for your text message expressing an interest in our Dual servo project, unfortunately the email address you provided does not work. So here is a copy of my draft answer I couldn't send!



    As the project has progressed, I have to say, I keep on learning more and more, so yes I can pass on quite a bit of information.


    Essentially the Dual 7" servo will be of interest to any owner who has either the Metro servo, or the older Cortina 7" servo fitted to their Marlin. It is unlikely to offer any benefit to cars where the standard Sierra servo was fitted.

    The crux of the matter is Ford designed the Sierra braking system around the standard Sierra servo in conjunction with all the other standard components. When adopted complete in a Sierra based Marlin, the brake system works very well in a lighter weight car. Marlin introduced their own pedal box for engine gearbox combinations requiring an hydraulic clutch, and to make more engine bay space for the likes of the Rover V8, and latterly BMW engines with slanted blocks and double overhead cams. This pedal box required a smaller diameter servo to fit inside the engine bay side panel: hence the smaller diameter Metro unit was chosen. However, in doing so, Marlin have reduced the servo assitance, and the brakes on Cabrios, Hunters and Sportster have been viewed as barely adequate: this feeling has been exaserbated by modern cars having ever bigger servos fitted (in conjunction with ABS) requiring very little brake pedal pressure from the driver.

    The Dual 7" servo offers almost identical assistance to the standard Sierra servo whilst retaining the smaller 7" diameter of the Metro (& Cortina) servo: it has a very similar stud fixing pattern to the Metro servo, making it a simple physical swap.
    I have designed and sourced a laser cut adaptor plate which bolts to the new Dual 7" servo, and accepts the standard Sierra master cylinder. BMW based owners have found the BMW master cylinder will not fit the Dual servo as it has a closed face, and will not accept the depth of the BMW m/c body. These owners have had to source a new Ford Sierra 22mm bore master cylinder (around 45 new). Once fitted the brakes perform equally well in a Ford or BMW system.

    To put numbers to the difference between a Metro servo system and the Dual 7" servo, one BMW Sportster owner has carried out a series of brake tests on an airfield. From a steady 70mph, the Metro assited brakes slowed the car from a fixed point to stationary over an average distance of 210 feet, measured over four tests, braking as physically hard as he could. With the Dual 7" servo fitted the average distance was just 103 feet, without maximum leg pressure.
    Pressing harder, and taking the brakes to locking point on a fith run, reduced the stopping distance to just 80 feet. For the sake of his tyres he did not repeat the test!

    The explanation is that brakes require a minimum critical pressure to work - discs more than drums. The standard Sierra set up was designed by Ford to provide that critical pressure. The Metro servo lacks sufficient diaphragm surface area to provide that critical pressure in the Marlin pedal box design set up. The new Dual 7" servo, has the required surface area, and takes the brake system back to the way Ford intended it to be in the Sierra.

    This whole project is very well documented on the Madabout Kitcars website, and will take you through most of the questions and answers you may have as we worked our way through the project. Although there are 16 pages, you'll soon be able to skip through and pick up the telling bits of information, and issues we encountered.

    http://www.madabout-kitcars.com/foru...t=3149&page=16

    If you are still interested, give me a call on 07968 835101 anytime (I work from home, so anytime is ok).

    Regards

    Mike
    Last edited by Mike; 27-06-2012 at 08:13 AM.
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  2. #12 Re: Dual 7" Servo : Better Brakes 
    frequent forum contributor Club Member
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    Hi Mike,
    I realise that i am very late in showing interest in the Dual Servo purchase but I see you may have two Dual servo's available in the near future and that one has already been taken. If the second is still available i would like to purchase it from you if possible. Will try and ring on the number you posted in your reply to Mikejj.
    Regards Mike Woodley.
    What is it about the name Mike and Marlins?
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  3. #13 Re: Dual 7" Servo : Better Brakes 
    frequent forum contributor Club Member Mike's Avatar
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    Quote Originally Posted by mike.woodley View Post
    Hi Mike,
    I realise that i am very late in showing interest in the Dual Servo purchase but I see you may have two Dual servo's available in the near future and that one has already been taken. If the second is still available i would like to purchase it from you if possible. Will try and ring on the number you posted in your reply to Mikejj.
    Regards Mike Woodley.
    What is it about the name Mike and Marlins?

    Hi Mike

    As per our telephone call I may have one available - it depends what MBM decide to do. I am away on holiday next week, so will let you know when I get back.

    Mike
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  4. #14 Re: Dual 7" Servo : Better Brakes 
    frequent forum contributor Club Member Mike's Avatar
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    Quote Originally Posted by Mike View Post
    Hi Mike

    As per our telephone call I may have one available - it depends what MBM decide to do. I am away on holiday next week, so will let you know when I get back.

    Mike
    Hi Mike Woodley (there being so many Mikes!)

    I have had a couple of other owners express a late interest in the Dual 7" servo kit. If there are a couple more interested owners out there sitting on the fence, who would like to join join in, I can order one last case of 6 servos.
    It is clear the interest/demand has now almost run its course, having supplied 45 members already, so I will only order a case of 6 if I have committed interest for at least 5 of them.

    For anyone still sitting on the fence thinking " I perhaps should join in while I can" - this is THE last chance of having someone organise the complete kit for you. After this batch - I will not be ordering any more.

    Regards
    Mike
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  5. #15 Re: Dual 7" Servo : Better Brakes 
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    Hi Mike,
    I tried to reply to your pm but not sure if you got it.
    Yes i am interested. You can contact me on 07763213288 or mike@thewoodleys.eclipse.co.uk.
    Regards Mike.
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