SERVO FITMENT

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chris741963
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SERVO FITMENT

Postby chris741963 » Fri Aug 02, 2019 11:24 am

Hi, Does the servo conversion make standard 8" drum brakes any better and how much improvement if any do you get. If recommended which kit is the best to buy?

oliver90owner
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Re: SERVO FITMENT

Postby oliver90owner » Fri Aug 02, 2019 12:21 pm

Doesn’t make the brakes any better - only reduces the force required at the pedal.
If the wheels can be locked without a servo, it would just be easier to do the same with a servo fitted.

simmitc
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Re: SERVO FITMENT

Postby simmitc » Fri Aug 02, 2019 2:20 pm

It depends what you mean by "better". A servo will not improve efficiency od remove brake fade undr heavy use, but will make it easier for the operator to apply the maximumk force to the pads - you would use less effort on the poedal to achieve the same braking. A standard system in good order should be able to lock or four wheels wothoiut a servo. If not, then service the rest of the system. If you want to amek it easier to press the pedal then fit the servo.

StillGotMy1stCar
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Re: SERVO FITMENT

Postby StillGotMy1stCar » Fri Aug 02, 2019 2:49 pm

Standard drum brakes by design/position of the cylinders have a self-servo effect on the front wheels when traveling forwards. Discs don’t have this effect.
I suppose there is a perceived better braking with lighter brake pedal force with a servo more like a modern car that have too much servo assistance these days.
I can remember having this discussion with the MOT tester I used to use and he was of the opinion to keep it simple, the brakes were designed to work when new so why change it.
So if you feel you need a lighter pedal then go for it.
There is a theme developing here, perhaps someone with drums and servo should comment now.
Regards John

geoberni
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Re: SERVO FITMENT

Postby geoberni » Fri Aug 02, 2019 2:55 pm

Well Basil had a servo fitted when I brought him and I've never driven a Moggie without one, so I can't really compare. Thinking back to the last time I had a car without a servo... 1977, I'm afraid in the last 40+ years I've driven too many vehicles ..... :wink:
But I generally concur that it's ease of pedal operation, rather than 'better braking'.
Basil the 1955 series II

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Myrtles Man
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Re: SERVO FITMENT

Postby Myrtles Man » Fri Aug 02, 2019 4:27 pm

It's probably reasonable to assume that most (virtually all?) Morris Minor drivers these days also drive more recent vehicles, all of which have servos fitted. As a consequence, our reactions are programmed to expect an immediate and reassuring effect at the first light pressure on the brake pedal, which ain't the case with un-servo'd drum brakes and which can lead to an involuntary slight concern/sheer panic (delete as appropriate) when nothing much seems to be happening, especially so if the well-servo'd traffic in front is driving on its brakes, stop-start style. :o
Last edited by Myrtles Man on Fri Aug 02, 2019 6:33 pm, edited 1 time in total.

ampwhu
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Re: SERVO FITMENT

Postby ampwhu » Fri Aug 02, 2019 5:41 pm

I have a series 2 MM with discs on and no servo fitted as well as having a A30 with discs and no servo. in all honesty, both cars have superb brakes so I really don't think there is any need for a servo unless you require one due to leg strength.

ManyMinors
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Re: SERVO FITMENT

Postby ManyMinors » Sat Aug 03, 2019 7:39 am

Disc braked cars like the BMC 1100/1300 range, MG Midget and MGB and the early Marina all did without servos originally didn't they. We've all got a bit feeble it seems. I've certainly never felt to need to equip my Minors with servos and prefer to keep things as simple as possible, finding that a simple car is a reliable car :wink:

IslipMinor
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Re: SERVO FITMENT

Postby IslipMinor » Sat Aug 03, 2019 7:57 am

My logic for fitting a servo to our Minor after fitting disc brakes 20+ years ago was very simple - I did not want to have to 'get used' to a very different feeling to the brakes from a modern car, at the same time as I needed to stop quickly in busy traffic. Modern cars with ABS, brake assist etc., just stop quickly, so long as the driver presses the brake pedal hard enough; I also want to 'just' stop, not have to figure out how much harder I need to press the pedal at the same time!

One fact - it is easier to modulate the brake pedal pressure with a lower pedal load than with higher. The result is likely more control in hard braking situations, i.e. unusual or emergency.

Even Morris recognised that the earlier 7" drum-braked cars needed too much brake pedal pressure, and reduced it by almost 20% with the introduction of the 8" brake setup.

As always, everyone has their view, as they should, so long as it's safe and legal, which is what makes this board so interesting!

Anyone near to Oxford wants to try a disc braked car with a servo as a comparison? Just let me know.
Richard



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myoldjalopy
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Re: SERVO FITMENT

Postby myoldjalopy » Sat Aug 03, 2019 9:07 am

I'm with 'ManyMinors' on this one............and would recommend the OP saves his money for the inevitable repair jobs which will crop up sooner or later! :wink:

Myrtles Man
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Re: SERVO FITMENT

Postby Myrtles Man » Sat Aug 03, 2019 9:21 am

myoldjalopy wrote:
Sat Aug 03, 2019 9:07 am
I'm with 'ManyMinors' on this one............and would recommend the OP saves his money for the inevitable repair jobs which will crop up sooner or later! :wink:

Including front-end damage perhaps? :D

paul 300358
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Re: SERVO FITMENT

Postby paul 300358 » Sat Aug 03, 2019 11:15 am

I found that disks and servo became more relevant when I fitted wider wheels.

pgp001
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Re: SERVO FITMENT

Postby pgp001 » Sat Aug 03, 2019 11:46 am

The OP originally asked if fitting a servo would improve 8" drum brakes, the answers all seem to be giving advice on whether to fit discs.
I have a traveller with front discs and servo that were fitted when I bought it, and apart from having to replace the discs because one was warped I am entirely happy with this set up.

In a sort of answer to the original question however, many years ago I added a servo to my drum braked mk1 Ford Escort, the perceived increase in braking power was incredible, this would be due to the fact that the brake shoes have a much larger working area than pads do.

BUT.......There is always a BUT. A servo does not cure drum brake fade. Once the drums got hot they were useless. This is not normally a problem with a disc brake set up.

Phil

philthehill
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Re: SERVO FITMENT

Postby philthehill » Sat Aug 03, 2019 1:07 pm

Fitting a servo will not increase the braking efficiency of the 8" drums but as stated above it will reduce the pressure required to push the pedal down.
You can get the same effect by pressing harder on the pedal but that requires effort.
The efficiency of the brake is limited by the manufactures design in this case the 8" dia drums and the internal dia of the wheel cylinders and the internal dia of the master cylinder. The type of brake lining material and its coefficient of friction also has to be taken into consideration.
To make the Riley 1.5 front drum brakes more efficient they were increased in size to 9" dia and the shoes were nearly three times as wide as the Minor shoes.

So to sum up - fitting a servo will increase the hydraulic line pressure so causing the brake lining material to press harder against the drum which may or may not be more efficient than pressing down hard with ones foot.

As regards my own brakes - I do not have a servo but have Marina 9" dia discs on the front, Wolseley 1500 8" drums on the back and the small internal dia master cylinder. The car stops very quickly and efficiently and I can lock the wheels if required with a minimum of pedal pressure


ManyMinors
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Re: SERVO FITMENT

Postby ManyMinors » Sat Aug 03, 2019 3:17 pm

Myrtles Man wrote:
Sat Aug 03, 2019 9:21 am
myoldjalopy wrote:
Sat Aug 03, 2019 9:07 am
I'm with 'ManyMinors' on this one............and would recommend the OP saves his money for the inevitable repair jobs which will crop up sooner or later! :wink:

Including front-end damage perhaps? :D
Well, I've never run into anything in my drum-braked Minor and I don't have any trouble bringing it to a halt. I suspect that people who claim that Morris Minor brakes "aren't very good" simply don't have them working very well due to lack of maintenance and poor quality components. My standard brakes work perfectly adequately on my standard car. If my car was much modified and travelled much faster then certainly I would expect to have to uprate the brakes too. Horses for courses :wink: If somebody feels that the standard brakes don't suit their needs or driving style then uprating them is sensible if it results in enjoying the driving experience more :)

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myoldjalopy
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Re: SERVO FITMENT

Postby myoldjalopy » Sat Aug 03, 2019 5:18 pm

Myrtles Man wrote:
Sat Aug 03, 2019 9:21 am
myoldjalopy wrote:
Sat Aug 03, 2019 9:07 am
I'm with 'ManyMinors' on this one............and would recommend the OP saves his money for the inevitable repair jobs which will crop up sooner or later! :wink:

Including front-end damage perhaps? :D
Ha ha! :P But, all joking aside, I have never had any front-end damage in over 35 years of driving drum-brake Minors as my only vehicle. However, I once had rear-end damage from a white van which ploughed into the back of me - doubtless it was fitted with a servo! :wink:

Nickol
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Re: SERVO FITMENT

Postby Nickol » Sat Aug 03, 2019 7:04 pm

interesting read on the above.

i have a servo assist already fitted on mine but am never sure if it really operates correctly or not. I do Need to apply good pressure to stop quickly but I have never been able to lock the wheels in braking even though the entire System has been renewed i.e new MC, Original (not replica) brake cylinders front and back, new mintex shoes and new brake hoses........I nearly wrote etc but there is not anything alse except proper adjustment.

The Brakes do work and satisfy the TüV inspection but I am not so sure they are really 100% correct. Ah yes, rear brake drums are also new.

I do not really expect to get any tips as I think almost everything that could have been renewed has been done. :-?
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philthehill
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Re: SERVO FITMENT

Postby philthehill » Sat Aug 03, 2019 9:20 pm

With a servo fitted you should be able to lock the wheels without difficulty.

Has the servo been stripped, examined and rebuilt. Is the servo diaphragm serviceable?


oliver90owner
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Re: SERVO FITMENT

Postby oliver90owner » Sat Aug 03, 2019 11:40 pm

ManyMinors wrote:
Sat Aug 03, 2019 7:39 am
Disc braked cars like the BMC 1100/1300 range, MG Midget and MGB and the early Marina all did without servos originally didn't they. We've all got a bit feeble it seems. I've certainly never felt to need to equip my Minors with servos and prefer to keep things as simple as possible, finding that a simple car is a reliable car :wink:
Yes, they would have used softer pads than many servo-fitted systems.

On my Cortinas, when we fitted servos we fitted the harder pads. There was a very considerable difference in braking with the harder pads with and without the servo. But we did not alter master cylinder (piston diameter) at the time. The brakes worked and that was that.

As I recall, the servo pads had copper fragments included - presumably for better resistance to heat fade. Standard discs/pads (non-servo) faded quite badly if used too exuberantly. OK most of the time for a 1200 Cortina but just not good enough when a 1500GT engine was dropped in...

I expect that the softer pads would have worn out rather more quickly, but I can’t recall us doing other than fitting the harder pads, supplied for the GT models, when adding servos.

IslipMinor
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Re: SERVO FITMENT

Postby IslipMinor » Sun Aug 04, 2019 9:29 am

Harder pads?

I had a Sunbeam Rapier MkII Convertible in the mid 60's, which had the standard drums brakes. They faded very easily with any mildly enthusiastic driving, so fitted the later MkIII front discs, which never included a servo. I also fitted Ferodo DS11 pads and VG95 rear shoes. They worked extremely well, BUT the pedal pressures were very high and they did not work that well straight from cold, which was a characteristic of high performance pads at the time. Today's equivalent pads just work.

The Rapier was followed by a Humber Sceptre that used the same braking system as the disc-braked Rapiers, but with a servo as standard! Even after fitting the same DS11/VG95 combination, the brakes were very much 'nicer' to use.
I'm never sure if it really operates correctly or not
Leave the engine idling for a minute or so to make sure that the servo is fully 'charged', turn off the engine and gently press the brake pedal a number of times. With each pedal press you can often hear the servo working, and if it is the pedal will become progressively 'harder' as the servo effect is reduced in parallel with the vacuum reservoir becoming more and more depleted.

If the pedal feels the same after 10 or so 'presses', it could well be that the servo is nor working very well/at all. Is there an inline non-return valve fitted? If it is, is it fitted the right way round?
Lockheed Servo Non-Return Valve.jpg
Lockheed Servo Non-Return Valve.jpg (44.41 KiB) Viewed 253 times
Richard




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