It's irrelevant whether it's single circuit, dual circuit, dual circuit with additional diagonal split in the event of one circuit failure to ensure both front brakes still operate, with or without ABS, the servo only increases the pressure into the master cylinder from the pedal.

In other words, you push on the pedal with 1lb or 10lb of force from your foot and it will translate that into 1.9lb or 19lb of force into the master cylinder - not taking into account the leverage from the pedal of course.

Without the servo, about twice as much pressure on the pedal will be needed for the same braking force at the wheels, whether those wheels are fed with a single circuit, dual circuit, dual circuit with additional diagonal split in the event of one circuit failure to ensure both front brakes still operate, as for a system with a servo.

This video gives a good (but Americanised) explanation of how the brake servo works. As you can see it doesn't even mention the master cylinder, single, dual or split braking circuits as they are a separate entity to the servo :

https://youtu.be/wbTUvp-tD5M

Only 2-3 minutes, it will help my words above make a lot more sense! :thumbs_up:

Hi
no he is talking about a in line servo MGB type it all you can get at that money
so you cant use them

https://www.ebay.co.uk/itm/392904728282?

this one is 56 £

That's a remote servo and master cylinder kit as fitted not only to the MGB but Rover P6 and many Land Rover models. I think the one you're thinking of was its predecessor which, if memory serves correctly, used a normal master cylinder on the bulkhead with a hydraulic line to the remote servo/MC assembly and because of bleeding problems and leaks, the system was recalled and a mechanical link fitted to the remote servo/MC and brake system such as the one you've linked to.

The early ones (i can't quite remember how they were meant to function) but the fluid was shared (maybe recirculated?) between the two MCs which caused much of the problems and yes, in that case using a single line servo on a dual circuit brake system would cause a problem.
I seem to recall BLMC as they would have been at the time recalled all MGBs with the "inline brake booster" because of the problems with it. I'd all but forgotten about that horrible thing, maybe someone recalls them better than i do and can shed more light on it but adding a normal servo to any braking system will improve matters.

Purely anecdotal, the servo on my Rover developed a leak a few years back, caused rough idling (vacuum leaking out/air leaking in), poor braking and a lot of hissing, worse when i used the brakes which, being auto, i had to a lot at a standstill to prevent it "creeping".

I simply unbolted the MC from the servo (2 nuts and washers) on the engine side, unbolted the 4 nuts on the cabin side, removed the vacuum connection then eased the servo away from the bulkhead until it was clear, eased the MC off the front of it (called the back in that vid i linked to) then slid the servo out sideways over the rear exhaust bank.

To fit the replacement, all i did was "Haynes it" then test, all good. The servo waas secondhand bought via ebay i think (several years back and i've been asleep since) and could have come from almost any model in the 800 range (except the 825 KV6) so may or may not have had ABS, might have been from a diesel or any of the myriad 2.0 models produced but all used the same mounting points and servo.

The point of this slightly off-topic anecdote is that most servos are simple animals and can be found in several different vehicles.

As long as the servo the OP gets is suitable for his model, it won't be an inline booster type and should be easy enough to retrofit and return his brakes to easier operation. :thumbs_up:

[QUOTE=[I]Laird Scooby;2771430]It's irrelevant whether it's single circuit, dual circuit, dual circuit with additional diagonal split in the event of one circuit failure to ensure both front brakes still operate, with or without ABS, the servo only increases the pressure into the master cylinder from the pedal.[/I]

Only just reading this. I thought that add on aftermarket boosters were fitted between the master cylinder and the rest of the system. So the effort into the master cylinder is the same as it was before assistance, but it is magnified into the wheel cylinders.

[QUOTE=norustplease;2775032]A booster - whether it is after market or not - does indeed just increase or boost the pressure in the slave cylinder / caliper.

The effort required comes across to the driver as a more subjective (as well as objective) experience. You feel as though you are not having to press down as hard and can (potentially) reduce speed more easily.

#####

My impression of the information given in this thread comes across as being potentially confusing.

ABS - advanced braking systems - do not (generally) contain a boosting element and so do not increase the braking ability in terms of the behaviour of the friction material rubbing against the braking surface. They do, however, for the majority of drivers provide a better safer system which helps to prevent wheels from locking up.

The chances of a vehicle stopping within a shorter distance fitted with some sort of anti-lock / ABS system vs a vehicle without ABS - when there is a chance that the wheels / tyres will skid under braking - is much greater for the ABS fitted vehicle (which is why it was invented in the first place!)

[QUOTE=norustplease;2775032]I've not seen anything like that and to be honest, i'm glad. Fitting a booster after the master cylinder could cause an imbalance across the various different circuits (if more than a single line) so it would make more sense to fit the booster on the master cylinder to increase the input pressure from the brake pedal. That way all lines get the same amount of increase.

[QUOTE=Army;2775035]Now that really is confusing! :err:

Why, then, do both my cars, both equipped with ABS - Anti-lock Braking Systems - have servos from the factory? Even the Jensen FF which had a mechanical anti-lock braking system developed by Dunlop (think there may have been someone else involved too but can't remember just now) had a servo!
Also, the oldest car i've owned so far, a 1967 Rover P6 had a servo - granted it was remote living down near the headlamps if memory serves (it was 35 years ago!) but a direct mechanical link to the brake pedal and then after the servo was the master cylinder.

The servo is there to reduce the effort needed by the driver on the pedal to bring the vehicle to a stop quickly. No more, no less.

Just a quick recap I fitted a new remote booster from Brookhouse and it’s significantly improved the breaking response, I now have confidence in them. Remote servo were common it’s not unusual to see them on 60’s cars
I don’t think anything was wrong with them before just the amount of effort needed, I have a 74 alfa so I’m used to driving non ABS brakes and your right ABS does not add anything to brake pressure or leg effort it’s just anti lock up

[QUOTE=Laird Scooby;2775039]I don't quite understand what is confusing or why there is confusion (!)

As you describe the servo / booster up until now is more often than not a different piece of the braking system.

Whilst some times a part of the ABS system is called the "pump" it isn't (in the cases I've come across so far at least!) a part that increases pressure like a servo / booster - that's the job of the servo / booster.

There's nopthing, however, to stop say electric vehicles that are going to struggle to produce vaccum naturally from using combined braking systems that not only help with the feel / effort of braking combined with some form of stability / anti-skid features.

#####

The point I was trying to make - which might not have come over clearly - is that there is a reason why ABS was invented.

As I am sure you know - under hard braking with out ABS the wheels can lock up and the vehicle skids. Generally speaking (ignoring drifiting and competetive driving) skidding is considered to be a bad unsafe thing (!)

When I took my driving lessons I was taught to pump the brakes to try to stop the vehicle from skidding. I assume pupils are now taught to keep their feet firmly on brake pedals these days to get the full advantage of the effect of ABS...

...in this thread my impression of the information given thus far is that ABS doesn't improve braking. In terms of pushing friction material onto the braking surface it generally doesn't help (like a booster / servo can) but in terms of bringing a vehicle to a halt under hard braking where skidding will / might happen it is a system that is intended to reduce braking distances and improve safety

[Probably wasn't necessary to be so pedantic but hey it has happened now!]

Indeed no one here has explained ABS properly ... it's sole purpose is:
TO BE ABLE TO STEER whilst using full brake pressure rather than the wheels locking and going in a straight line where ever you steer ...