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MG Midget and Sprite Technical - Brake Servos

Does anyone have any experience of quality and reliability of "unbranded" servos sold by our regular suppliers compared with the so-called branded ones? Are branded "Lockheed" or whatever anymore than a name nowadays? Price differences between the two can be considerable.
G Williams (Graeme)

Cant comment on servos but from experience of master cylinders I would buy branded. Lockheed is still owned by AP (dont know who controls them these days) and although they may not be made in this country quality still seems good. After reading of other peoples woes of clutches I also paid more for an AP clutch and have no complaints after 3 years although it was made in one of the former Eastern Bloc countries.

Trev
T Mason

AP was broken up several years back. Most production is now East European and the servos are still boxed in Lockheed boxes under the lable CAPARO.
Do not buy the unbranded ones as many have failed.
Shop around as you will find Minor specialists sell the same item much cheaperthan the big MG companies.

Jonathon
JLH
J L HEAP

Thanks Jonathon and Trev.

So are the "Lockheed" ones reliable especially since they are only Lockheed in name? Is Caparo available as its own brand but similar qaulity?
G Williams (Graeme)

The best quality servo - one that will never fail or wear out - is the one that is not fitted; medical issues apart there should be no requirement to fit a servo on a midget. The perception that one is needed is often due to other problems within the braking system. (yes I realise that's not what was asked...)
David Smith

wow, you put both what I'd have normally posted and your reply to my post ! :)
Nigel Atkins

Ah, the for and against brake servo topic rears its head again!

I agree with David. Poor brakes on a Midget are almost always due to wrong adjustment, and poor maintenance resulting in imbalance. Adding a servo will very probably make them feel better - until the day comes when you need to apply the brakes in an emergency. The added effect of emergency braking with a servo on an imbalanced system will then very likely result in uneven braking and on a wet road result in a spin.
Guy W

I totally agree re servo and drum brakes, (should not be done IMO) but if a better feel is required for disc brakes then I see no issues at all. A servo will not improve your brakes simply the feel. Personally I prefer a servo to be fitted with discs, but also appreciate the 'natural' feel sought by others. No right or wrong here, unless you run drums all around.
As a rule if you see a servo for under 100 leave it alone. Trade price on a proper Lockheed /Caparo unit is over 100 for small companies, the big hitters obviously less. Beware the cheap servos in Lockheed boxes they are to be avoided at all costs.
J L HEAP

I fitted the 'Powertune' version (from Moss) about 4 years ago and its working well - no issues with silicone fluid.

When I bought it I had both units (original and Powertune) on the counter and could not see any visible difference.

Won't enter the servo / no servo discussion - its a personal thing, but changing from over servoed moderns to occasional Midget use these days, it takes some while to reconvert my brain/foot how hard it needs to push for a sharp stop.

R.
richard boobier

I'm in the pro servo camp as anything which helps improve the braking efficiency, even for something as well braked as a standard Midet, is IMHO, to be considered. No doubt others have/will say it only affects the feel of the brakes but I find I need less effort for the same braking effect which may just help one day especially in modern driving conditions. Of course it may not make a ha'path of difference but I feel safer with it fitted - rather like having a thermostatically controlled electric fan instead of the mechanical one for those times you're stuck in modern traffic or electronic ignition which doesn't degrade and lose its efficiency.

Don't buy a cheap one, not with something as critical as brakes. I bought one about 5 years ago from Welsh MG and it cost about 115 then, sorry don't remember the make but it has worked well and like Richard's, is happy with silicone fluid.
Jeremy 3

I thought servos were fail-safe, in that if they pack up, you just get back to standard braking.

I haven't got one, I've never felt the need -- on my Sprite, but I can see why some do.
Lawrence Slater

yes Lawrence - but if people cannot work the brake pedal properly and 'need' a servo in normal driving, they are hardly likely to press hard enough in the panic moment of an emergency...
David Smith

Yup good point. It would be a nasty surprise, suddenly finding you can no longer brake with your little toe. :(
Lawrence Slater

Well some clearly have not tried a servo - the ones supplied for our cars are not of such a ratio to be 'over servoed' and still give very good brake feel.

Deffo not 'your little toe' pressure - well not mine !

R.
richard boobier

Hi Richard, I was exagerating to make a point. But having said that, I could use very light pressure on my 318iS BMW pedal, and still lock the brakes. So that servo was pretty active. Never tried one on a Spridget though, but I'm sure my mate had one on his mini years ago; -- so long I've forgotten what it felt like.
Lawrence Slater

ive got disk brakes on the front, and after rebuilding the car using the pads and disks that came with it i was very worried and dissapointed with the brakes.
Yes everyone told me they should be good, but they just werent...
I looked at buying a big brake kit (from JLH as it happens) but he said on the road you wouldn't notice much difference over std...

So i ordered some new EBC disks and greenstuff pads.. much cheaper...
put them on and bedded them in and i cant believe the difference it made, i can now lock up the front wheels and get a nice progressive feel and the pedal has a soft feel like in a modern.

after my experiance i'm in the 'dont need a servo' camp...

However i have completely renewed my hydraulic system and put on two master cylinders, one for front, one for the back and a brake bias bar. and extended the brake pedal by 3 inches...
Andy Phillips (frankenfrog)

"and extended the brake pedal by 3 inches..."

I bet that definitely has something to do with it. Extra mechanical advantage, -- just like a servo really, only no vacuum assistance needed.

How long is the standard pedal? Some genius on here ought to be able to calculate the extra force available for the same presure, due to the extra 3" length.

Archimedes law of the lever.
"Give me a place to stand and with a lever I will move the whole world."

Lawrence Slater

yes, thats why i did it...
The PO had put a servo on from unknown source, but it was very small diamater, so not much advantage, maybe 2 or 3x . But to get it to fit they had to mount it high on the top of the footwell and put an extended arm on the top of the pedal to reach it.
The final result was a pedal giving about 1.5:1 leverage plus to advantage of the servo.
I didnt like it, so after research, mainly on the willwood site i went for an 8:1 pedal ratio as with the willwood ready made pedal box's.
it works very well.

However i had to make a new pedal box support which has moved the pivot point up and into the engine bay. which after seeing daniels video's i'm going to box over with a thick aluminium box.

clutch is cable operated.

pic of pedal box below


Andy Phillips (frankenfrog)

pic of old arrangement below, i think it was off a datsun.
PO had made a bracket to fit it, but not a satisfactory arrangement.

much better /easier to use the remote type i think....

Andy Phillips (frankenfrog)

Andy,

My answer was given for your particular driving conditions where you were not going to 'push' the limits of the std brakes let alone our uprated kits. If the reverse was the case then sure there is a vast difference of performance on offer.
Glad you achieved what you wanted with a simple cheaper fix though.
J L HEAP

Hi JL,
understood that, if i was on the track or other types of competition , then the bigger brakes would be a worthwhile investment. But for my mainly A-road driving then they wouldnt be required.
Thankyou for your advice and honesty in not trying to sell me something i didnt need ..
Andy Phillips (frankenfrog)

Andy: the standard Lockheed servo only gives a ratio of about 1.9

G Williams (Graeme)

mmm. so if the lockheed one gives only 1.9:1 then the old unit one mine would have given about the same as its a similar sort of size.
So, the PO added a big connecting arm to the top of the brake pedal to get it connected up giving a ratio of around 1.5:1

if you applied 1kg of force to the pedal you would get 1.5 out , but then add in the servo advantage at 1.9:1, then that becomes 1.5 x 1.9 = 2.85:1.

i think the std spridget brake pedal gives around 5:1, so the PO actually made the brakes worse by adding the servo.

However if you use the lockheed remote servo together with a std pedal you would get 5 x 1.9 = 9.5:1 total advantage.

with my setup, which i am very pleased with i get 8:1.
Will wood racing pedal boxes give between 8:1 and 9:1.

All this only effects how hard you press the pedal of course, but its all about confidence, if you feel you have to press excessively then in the back of your mind are worries about what will happen when you really, really need the brakes..and that worried me..

So after consideration, i'm on the fence... if you have the normal pedal and dont want to go to the trouble i did, but want more confidence inspiring brakes then i think the remote servo is a good idea..

sorry for hogging the thread i'll shut up now ...;-)
Andy Phillips (frankenfrog)

The AP/Caparo units are available with different ratios, see here for details http://gentry.zxq.net/Remote_Servo_Installation.pdf and an application guide.


Jonathon
J L HEAP

JLH: the model which seems to come up for the Spridgets
is the LE72696 which is listed as the 1.9 ratio.

However I see the LR17814 is also listed although I couldn't see a ref to its spec in the pdf you link to.
Elsewhere I found a note to say that one is 2.9
Considerable difference! I wonder whether that would be "overdoing it"?
G Williams (Graeme)

I drove a Sprite with a Servo today.

I can well understand why people add them for the "comfort" factor, if I can put it that way. I liked it. If I got one cheap, I might add one m'self.
Lawrence Slater

One of the reasons for servos used to be to compensate for very hard non-fade competition pads. Because standard pads are inclined to fade, competition pads are often used. These are a lot better nowadays and work perfectly well without need of a servo. But it used to be the case that competition pads were very hard and needed significantly more pressure to get them to work at all. Hence the use of servos for competition use, where they really were needed.

This was then followed by those interested in "bolt on performance" as a popular upgrade to normal brakes, to copy the successful competition cars. On a car as light as a Spridget, they may seem to make driving more comfortable, but they really are not necessary. I would still class them as a form of bling!
Guy W

Early cars were engineered for asbestos linings which gave excellent bite and feel.The modern grey, sometimes weaved asbestos - free linings do give a wooden feel,and require much higher pedal pressures to achieve the same retardation. So for drum brake cars at least,a servo can produce a lighter pedal, although the assistance can sometimes be a little abrupt. You can of course opt for NOS linings if you search eBay, but under the Control of Asbestos Regs it's supposedly illegal to possess to supply, or indeed sell them.
F Pollock

Another tea or coffee argument then. :)

As I said, having not previously driven a Spridget with a Servo, I drove one yesterday, and was impressed.

The fact that it requires so much less effort on the pedal, for the same results, was surprisingly pleasing. I had actually expected NOT to like it; maybe resent it even. But it had the opposite effect on me.

There is no doubt about it, driving a Spridget is not difficult, and nor is braking one.

However, the light touch on the brake pedal when a servo is fitted, did enhance the pleasure, at least for me.
Lawrence Slater

When I used to build kit cars and the like many years ago, I discovered remote servos were not "fail safe", and they could leak brake fluid internally which obviously would cause a total unexpected loss of brakes.
As a Midget has no space for a direct action servo, which only assists the brake application force, I would not consider fitting a servo to a Midget as it would have to be a "remote" type and therefore flawed.
I don't think one is needed anyway, as said by others but it is just something else, a very important something else, that could go wrong in a big way.
JB Anderson

It may be a lot of trouble to go to, but couldnt you use a direct action servo, but mounted remotely and activated by a clutch slave cylinder ?

so you press the brake pedal. then that moves the slave cyl, which presses in the servo actuator as if it was a pedal....

plenty of direct action servos in the scrapyards to play around with....

Andy Phillips (frankenfrog)

What's the frequency of remote servo failure?
Lawrence Slater

I am surprised that servo failure is a real issue anyway. Just about every modern car has a servo and failure rates would need to be zero, to several decimal places of accuracy! They just cannot afford to have any sort of failures at all. Well, not in a catastrophic way that is. Gradual loss of efficiency might be manageable
Guy W

We have been fitting these AP remote servo's for 20 years and have had no failures at all. Number fitted or sold must be well over 200 units.
J L HEAP

Oh so BMC got it wrong and had major problems when they fitted remote servo's to most B's in the early 70's !


My cousin and I have had factory fitted units on B's since 1972 and so far we have not had a problem - fingers crossed then.

R.
richard boobier

All this does underline the argument to stick to "quality" units. The Delphi Lockheed seems to be the product leader.

It isn't clear whether a non-return valve should be fitted between the servo and the manifold. The spec says "on high performance engines". Any views?
G Williams (Graeme)

Graeme,

I fitted a non-return valve as it was not clear in the instruction if really required or not.

I used a standard MGB version screwed into the manifold when I had the 2x 11/4" SU's. The Titan HIF6 manifold was tapped a bit close to the vertical part to allow the rather large 'nut' of the valve to fit - so had to remove the extreme edges of the 'nut' to clear.

R.
richard boobier

So the general concensus is, that remote servos are not that unsafe, and are more likely to be safe.

So it's still just a coffee vs tea issue. On this I had no preference until I drove one, and now I'm a convert. I like them.

My only bugbear would be where to locate it. I keep my tools where the remote would go, but I guess they could be relocated.

Lawrence Slater

This is quite interesting.

http://gentry.zxq.net/Remote_Servo_Installation.pdf
Lawrence Slater

Interesting read. Well found!
I have one of these Girling remote units. It was on my '71 Sprite when I got it in 1989, fitted above the passenger footwell, as I recall. But the car was in such a state that although I cleaned the unit up and repainted it, I decide not to refit it and it then went "into storage" somewhere, and I haven't seen it since. It wasn't with the 8" drum brakes!
Guy W

Interesting comment in there about the need for a U-bend below the non-return valve and the Servo unit. I would assume that would apply to low as well as high perfomance cars.

If so, I wonder if those who have experienced failures, may not have had the U-bend petrol trap.

I also see that Silicone fluids are NOT approved; at least on the Delphi/Lockheed products.
Lawrence Slater

This thread was discussed between 08/05/2013 and 21/05/2013

MG Midget and Sprite Technical index

This thread is from the archive. The Live MG Midget and Sprite Technical BBS is active now.