Announcement

Collapse
No announcement yet.

Brake Servo

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • Brake Servo

    Just wondering if a brake servo is necessary ?? Takes up space and pipes and extra brake line..

    My TVR Chimera 350 bhp and all the TVR's do not have one..

    Thoughts !!!

  • #2
    Re: Brake Servo

    Interestingly I was just this weekend thinking about removing the servo on my car, which has been in place since it was built. When I built a Marlin in the 80's I didn't bother fitting one and never regretted it.

    When I first acquired my current car a couple of months back I must have locked up the front brakes half a dozen times, but this I just discovered is probably partly due to leaky rear brakes so probably not doing lot. I'm now able to stop quickly without locking everything up.

    Anyway, I sold a Vitesse 6 saloon to fund the Marlin and that did not have a servo yet I never felt like it was lacking braking force once you got used to the firmer feel.

    The Roadster is a lot lighter so I feel that it is adequately braked without a servo if you are talking about normal road use.

    I'd be interested in other responses as I'd quite like the extra space under the bonnet, mines got the Triumph straight 6 in it, which is very tight.
    - 9th owner of T693 SSC possibly a factory built Ford based V8 Sportster
    - 4th owner of Q309 RNV, an early Cabrio built by Bob Copping, owned Doug & Liz Billings for 16 years
    - 9th Custodian of JRR 929D, Triumph Vitesse based special Paul Moorehouse built prior to the Triumph Roadster kits.
    - 8th owner of Roadster chassis number 2395. Now owned by Barry!
    - Builder of chassis number 2325 (PKK 989M) in the mid 80's. Now owned by Eric & Lynne.

    Comment


    • #3
      Re: Brake Servo

      Interesting thoughts.
      The Roadster uses a shortened Marina brake pedal so more effort for equivalent brake pressure but the Roadster is lighter than a Marina so less brake pedal effort should be required for the same relative stopping capability. I presume we are talking disk brakes at the front, where most braking effort is required.
      Locking the front brakes is far more likely given the relative adhesion between tyre and road, far more significant that brake pedal effort. There is always the option of converting to vented Clio front disks.

      I can't remember the differences in master and slave cylinder diameters of non-servo Marinas, or those of servo assisted Marinas, but with a shorter pedal, a servo would be preferable. That is unless you have particularly robust leg muscles and like a direct feel.

      Whilst the servo is bulky, there are alternatives of mounting the servo remotely. As for pipe work there will be little difference, but ideally, as with modern cars, a dual/split system would be preferable for safety considerations so pipe work will depend on how you decide to make the split.
      Last edited by stevejgreen; 11-05-15, 03:37 PM.
      MOC member since 05/97
      1984 Marlin Roadster SWB.
      1800TC, Unleaded ported head, stage 2 cam. Ford Type 9 gearbox, Dolomite Sprint rear axle fitted with MGF disc brakes.
      Three core radiator, Renault Clio vented front discs.
      The reasonable man adapts himself to the world; the unreasonable one persists in trying to adapt the world to himself. Therefore all progress depends on the unreasonable man.

      Loads of Marlin Reference can be found documents here or there.

      Comment


      • #4
        Re: Brake Servo

        Echo Steve's comments.
        If you have a sloping drive you can soon ascertain the unboosted braking effort required .
        Personally, light as a Roadster might be, I would not want to rely on unboosted standard brakes (at least not with a B series or equivalent up front). Servo-assisted are bad enough due to the reduced-length pedal.
        Marlin Roadster, LWB...1860 B Series + Ford Type 9
        Renault Espace 54mm front calipers, vented discs, cycle wings and adjustable tie-bars.

        Comment


        • #5
          Re: Brake Servo

          Hi,
          I'll throw in my tupence worth, I have Roadster that with Ital servo brakes which I find the brakes are fine.
          I also run a Spitfire that I have just fitted a remote servo to after a few close shaves, modern cars braking hard in front of you can give you a few scares. Much better and feels a lot safer and you don't need to pull the steering wheel off trying to apply the brakes hard.
          There is no way I would choose to take the servo back off.

          Comment


          • #6
            Re: Brake Servo

            I have been giving this question a lot of thought for the roadster I am working on.

            Too much thought and not enough action

            I drive an MGB GT that does not have a servo fitted, so if brakes without a servo can stop that dead weight (have you ever tried to push one any distance, not easy) my thinking was that a roadster might be able to cope without a servo.
            I appreciated that a servo would make the brakes more efficient for less effort

            I understand the point that Steve makes about the pedal ratio being reduced as the pedals are shortened in the marlin.

            What I am looking at using is an OBP top mounted pedal box.
            This would bring several advantages.
            1. This unit has a pedal ratio of about 5:1 as opposed to the 3:1 with the modified Marina pedal box.
            2. The distance from the bulkhead to the face of the pedals is about 150mm, distance for the marina pedal box is about 185mm according to my measurements, so there is a small gain in legroom.
            The only thing that I need to check is if pedal travel will be limited by the step in the roadster bulkhead.
            3. With the pedals at the same height as the marina pedal box, the top of the unit is much lower this would allow the top of the bulkhead to be notched to introduce more rake into the steering wheel to move it away from the vertical position, as the the limiting factor has been the top of the pedal box casting.

            I have attached the diagram of the pedal box unit.

            Obviously there would be the small issue of a great big hole in the bulkhead to deal with going down this route.

            This will not be a problem for me as I intend to make a new bulkhead anyway.
            Attached Files

            Comment


            • #7
              Re: Brake Servo

              If you can see any blindingly obvious problems with this idea please let me know.

              I don't want to waste time, effort and more importantly money if there is a flaw in the plan.

              Comment


              • #8
                Re: Brake Servo

                Some early roadsters, mostly those without servos, were apparently prone to bulkhead cracking. This may have been exasperated by the main folds in the bulkhead panel being aligned in the same direction as the aluminium sheets grain pattern usually indicated by the direction of the identifying printing on the sheet. Long folds should be made accross the grain or with a generous radius.
                It all sounds like a good idea, but as you say the step in the bulkhead may be a limiting factor.
                the advantage you have with the pedal box shown is that it has two master cylinders for a split system that can be balanced front and rear. But these ought to be matched with the brake slave cylinders for best results.
                MOC member since 05/97
                1984 Marlin Roadster SWB.
                1800TC, Unleaded ported head, stage 2 cam. Ford Type 9 gearbox, Dolomite Sprint rear axle fitted with MGF disc brakes.
                Three core radiator, Renault Clio vented front discs.
                The reasonable man adapts himself to the world; the unreasonable one persists in trying to adapt the world to himself. Therefore all progress depends on the unreasonable man.

                Loads of Marlin Reference can be found documents here or there.

                Comment

                Working...
                X