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Brake Servo ?


Straightsix

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Hi all,

I’m curious to know how the Vitesse drives or should I say stop, should I wish to remove the brake servo.*

I understand Servos were not fitted as standard.

As an experiment, if I were to disconnect the servo vacuum hose and block it off, and do a trial road test, would that give me a true representation and feel as a non servo car, or would the hydraulic pipe work currently connected give a false comparison.

*Only thinking it would be nice to de clutter the engine bay.

Although the road test could decide otherwise.

Merry Christmas and Happy New year.

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I've never had a servo on any of mine and never felt the need for one. It affects the pedal feel, not the braking itself, but the actual brake setup should be adequate, maybe taking more pedal push than modern standards but all mine seem to have stopped as required, and certainly passed MOT. (Drum braked Heralds can be scary, though!!) Even the GT6 stopped very well with standard pads and shoes.

I honestly don't know how the servo hydraulics work, so will wait for a more knowledgeable comment on how merely disconnecting the vacuum would affect performance. 

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I have a servo, late GT6 mk3  had one as standard, a Girling. It's actually an MOT fail to remove one if it was fitted as standard and before you say "How would they know? The MOT man told me that. Bizarrely it has to be there but it doesn't have to work, there's no proscribed test for it. Which was fortunate for me as mine never worked, the car was 5 years old when I bought it and the servo didn't work. Only in recent times have I fitted a Lockheed which does work. 

As Colin says It doesn't make any difference to braking you just have to push harder OK for "Thighs like tree trunks" Lindsay to say, but I'm 75 you know :angry:. I put the Lockheed on precisely to make the braking more like a modern. I've had a servo fail in a modern and you REALLY can't stamp hard enough to get the same effect.

The servo sits between the Master cylinder and the slave cylinders introducing an interim cylinder which uses the vacuum to "amplify" the pressure to the slaves. I can see how disconnecting the vacuum might not give you the same as if you'd completely bypassed the servo. However, running around for 30 years with the non working Girling I can't say it was any worse than when I put the Lockheed on and initially it didn't work. 

On the mk3 the servo only works on the front wheels, on previous GT6s the servo was an option and worked on all 4 wheels. Odd! However once having got "into it" while fixing the Lockheed I tried it on all 4 wheels and very quickly put it back to front only. They had upgraded the rear brakes and putting the servo on all 4 made TOO much braking at the back.

The Lockheed's problem was it had been poorly assembled in China. When I took it apart and cleaned it up I got it going, Nirvana! I wouldn't be without it, if it fails it will get fixed very quickly. 

Doug

Edited by dougbgt6
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2 hours ago, dougbgt6 said:

On the mk3 the servo only works on the front wheels

IIRC the rear slave cylinders of the servo equipped Mk3s are different to retain the correct balance.

2 hours ago, dougbgt6 said:

on previous GT6s the servo was an option and worked on all 4 wheels.

My Mk2 GT6 has a Girling Powerstop servo acting on all four wheels and I suspect was a dealer fitted extra. There is a section in the WSM covering fitment. Brake balance is fine.

Ian

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Vitesses did not have a servo. Just find a quiet downhill slope and try it without the engine running. That will be what it is like without a servo. Compared with the early Heralds with drum brakes all round, they were perfectly adequate.

I had a 1600/6 with the smaller discs. That stopped really well. However, it had asbestos loaded pads!

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I have one in storage. New, never been fitted, Intended to go in the 13/60 "kit of parts". but now?. Maybe I will ultimately fit it to Plum, as the assist to ageing leg`s might be of some benefit. The BIG question is Location?. I note some have removed the battery to the boot as one option, Driver side opposite the tank?. Need some big long meaty cables though to take starting current without loss?. Has anyone ever created sufficient space by moving the battery/tray?.

As for removing one?. The overall effect will only be a heavier pedal, In my opinion, more so if the person who fitted it also changed the Master cylinder size, in order to get high(er) braking pressure?. Ultimately the design of the brakes Disk size/Pad area/composition, are surely the things that determine actual braking effect?.

Pete

Edited by PeteH
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I had two 1600/6's. The second one was a 1962 CV with a rotten chassis. It had a small servo fitted on the flat bit below the master cylinder. It was a very tight fit. It also had two semi downdraft SU's. I swapped the O/D box with my saloon that had a better engine and chassis and sold it, would you believe, at a profit in 1974.

If you move the battery to the boot, you only need one long stout cable. Make a good connection to the bodywork for the other one and all will be fine.

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17 hours ago, Ian Foster said:

IRC the rear slave cylinders of the servo equipped Mk3s are different to retain the correct balance.

The rear drums are 1/2" wider than previously and the cylinders 1/8" bigger diameter. I think they did it, found it was too much with the servo on all 4 and to correct it took the servo off the back end. Engineering by trial and error.

The cylinders are now hen's teeth, nobody has spares, except me! :) I got Paddock's last ever set about 5 years ago, they're waiting in my garage, somewhere.

Doug

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3 hours ago, PeteH said:

I have one in storage. New, never been fitted, Intended to go in the 13/60 "kit of parts". but now?. Maybe I will ultimately fit it to Plum, as the assist to ageing leg`s might be of some benefit. The BIG question is Location?. I note some have removed the battery to the boot as one option

I have a photo - somewhere - of a servo fitted down beside the engine block, between the side valence and the front of the block. If I can find it I'll post, but I've no idea of how the pipes were routed.

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12 hours ago, Wagger said:

Vitesses did not have a servo. Just find a quiet downhill slope and try it without the engine running. That will be what it is like without a servo. Compared with the early Heralds with drum brakes all round, they were perfectly adequate.

I had a 1600/6 with the smaller discs. That stopped really well. However, it had asbestos loaded pads!

 

Thanks for your replies,

@Waggerl like your simple suggestion regards to rolling down the hill with engine off -  not short of hills here!

Pleased I don’t have the steering lock/ignition version 🙂 I’ll be keen to try this  experiment out whenever possible and let you know. (Need to recover from an ankle sprain first)

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3 hours ago, Pete Lewis said:

we shorten the battery Tray  and moved it to the Ns to mount the servo between battery and heater  on the Vit6

the orig kit was mounted sideways next to the clutch slave which does make it a bit congested 

alt mount.JPG

Did It need a smaller (shorter) Battery, or did the standard battery still fit?. (It looks standard)? And does it still work if the "galley" Heater is fitted and not the Smiths?.

Pete

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On 24/12/2023 at 22:12, 68vitesse said:

Fitted servo in my Vitesse over master cylinders, no extra holes needed.

Regards

Paul.

 

IMG_2022-09-07-13-08-53-260.jpg

Neat Job! But looks a bit "tight"?. Did you have the modify the supplied bracketing?. I am thinking there will be more space on a 13/60?.??

Pete

 

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1 hour ago, PeteH said:

Neat Job! But looks a bit "tight"?. Did you have the modify the supplied bracketing?. I am thinking there will be more space on a 13/60?.??

Pete

 

Only used part off the supplied bracket, the bit around the nose of the servo, the rest I made from stainless strip using some of the pedal box holes using slightly longer bolts to fit them.

Little bit tight but had the advantage of not requiring any modifications to the car body or electrics.

Regards

Paul.

 

IMG_2023-12-27-11-01-05-508.jpg

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  • 1 month later...

Finally got around to taking the car out yesterday and trying the @Wagger method with engine off coasting downhill.

Before I set off I depressed the brakes numerous times to empty servo. (Brought back early memories of sitting in heavy downhill holiday traffic in Cornwall in my Corsair, coasting slowly with engine off, was ok until the servo emptied….. oh #%ck!! rock hard pedal and useless brakes. Not to be repeated !)

So back to the Vitesse, if I managed to empty the servo successfully, the brakes still felt effective during that little test, 

i won’t be looking to remove the servo anytime soon, especially as I have been buying lots of bits and pieces for the car with the intention to do those future jobs, trouble is, finding bits is easy finding the motivation to start is harder! 🫤

What to do going forward remains unclear at the moment 🤦🏼‍♂️

 

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Yes I think theres a difference between a brake system designed from the start with a servo and one which has had one added. The former is likely to have a higher ratio of assistance so feel much worse on losing it than the latter...

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2 hours ago, Straightsix said:

What to do going forward remains unclear at the moment 🤦🏼‍♂️

The standard Vitesse brakes are fine for me. Having driven autos for many years what I don't like is the small brake pedal! 

Iain 

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