Lockheed Remote Servo brakes locking on

[Grant]

Hi,

i have two remote servos and a balance bar

Need a bit of help working out exactly what has failed, whenever the brakes are used the fronts lock up gradually over a minute until they are on pretty solid. (pretty sure its just the front) If I then undo the vacuum pipe going into the front lockheed remote servo there is a hiss of air and the brakes free up again.

Is this a failing servo, or does anyone know if this can be fixed with a repair kit. not sure which brake servo's I have except they are lockheed, any easy way to tell the model

I supose I can jack the car up and see if the back lock up too! But I think the fault is the same

Grant

 

[Seymour Snerd]

Hi,

Is this a failing servo, or does anyone know if this can be fixed with a repair kit.

Sounds like both to me; I'm nearly certain it's the servo's fault if that's what you're asking. I've rebuilt Girling remote servos before; it certainly involved more parts and dexterity than (say) a master or slave cylinder rebuild. However, I found this site that makes rebuilding a Lockheed look relatively easy compared to what I remember of the Girlings. It also lists some model numbers and rebuild kit part numbers.

http://www.triumph-spitfire.nl/servoimages.htm

 

[Jim Cowden]

air valve
How Does a Brake Booster Work? | eHow.com

 

[Ian Anderson]

Grant

My advice would be to try and adjust your brake set up so you do not need the boosters

Reduce the Master cylinder sizes and retain a similar pedal "feel" without the boosters.

It will free up space, keep the system more simple and also save a pile of weight

Ian

 

[ronmac]

Grant, I have had the same problem in my case it was the small reaction piston (looks like a bullit with two seals on it) get the piston out and clean it up, also polish the bore that it goes into with bit of fine grade wet and dry rolled round a pencil until the bullit moves easily in the bore. this worked for me for a while but have now replaced the servos. the ones I fitted are original mk. 3 mini cooper s remote servos which I bought from mini-spares. Hope this helps.

Ron.

 

[Grant]

Hi All, thanks for the replys, I spent last evening rebuilding the thing with new seals etc, think I may give it a bit of a wet a dry treatmeant as it still seems a tad sticky. But I have pushed it back in now!!

How long did it last for?? bit worried if it sticks again it could happen quite quickly.

I'll update the post once i have it back in the car.

 

[Grant]

Been reading a few posts on the matter, as I have AP brakes on the front I could try running with out a servo on the front.
Is it a massive no no to leave the servo on the rear (Scorpio floating discs)??

 

[Andy Sheldon]

Grant

Why would you want to remove the servo?
You will drastically reduce the power of your brakes.

Thanks

Andy

 

[Grant]

Just reading previous posts, people have removed them, with no ill effects and actually improved the feel of the brakes.

 

[Andy Sheldon]

Grant

If you remove the servo you will have to push the pedal twice as hard to stop.

Its not much use having a nice feel if you can not stop.

Thanks

Andy

 

[Brett James-McCall]

Grant, in order to remove the serves, what Andy may mean, is that you would have to also change your master cylinders and/or the pedal itself. Don't forget your servo provides an increase in relative force on the pedal.

If you go on the Tilton website there is an area where you can put in your details about your brakes and car and they will recommend you cylinders based on the information shown.

If you do a search you should be able to find similar threads (I actually started one once). However, I'm on my phone typing this so can't search as easily.

Brett

 

[Brett James-McCall]

Here you go Grant:

http://www.gt40s.com/forum/gt40-tech-chassis-brakes-tires-wheels/19907-master-cylinder-sizes.html

 

[Andy Sheldon]

Brett

What I mean't is that what ever brake set up you have it will always be twice as good with servos.

I have driven cars that have had the servos removed and 4 pots fitted and the brakes are rubbish.

Having driven lots of these cars with 2 pots, four pots and 6 pots all with and without servos I can tell you servos fitted is best.

We are not in the 1950s anymore. Road speeds are higher and stopping distances shorter.

Thanks

Andy

 

[Mick Ridley]

Grant,.... here is an intresting thread about braking systems

How did you set up Brake Bias?

This chart will help you choose the correct master/cylinder sizes, to give you a balanced braking system. Put your values in the yellow columns, and the blue column will tell you what you need

Claytons brakes.xls

 

[Ian Anderson]

I accept everything said so far. And re Andy saying the boosters are a must - for some they are.

But at the same time if you can lock all for wheels without the boosters why do you need additional force?

On my particular car I have a 6:1 pedal ratio
No boosters
0.75 inch master for rears and 0.625 master for fronts
At Donnington I "overdid" entrance speeds into corners and could reasonably easily lock everything up!
Yes it does take some pedal pressure but my size 11 foot copes easily enough with that.

But if you want you grandmother to take my car for a drive she'd probably say the brakes were hopeless. - Two reasons - she could not reach the pedal unless she is over 6 foot tall (Set up for me at 6fot 3 inches and 18 stone)and secondly the foot pressure required.

So you need to decide what you want for your diving experience - you make a GT40 fit you and if you like a really light brake pedal - refit the boosters - if you like a firm pedal leave them off and adjust the system accordingly!

Ian

 

[Jim Cowden]

I agree boosters make for an easy drive.

I think if it is worked out you can get a good comprimise without boosters.
I have 5:1 pedal 5/8 front and rear masters, the car will pull 1g under brakes with not to much problem.

The pedal is not hard due to the master cyl sizes and it is not a long pedal,maybe closer to a boosted pedal.
I had a 3/4 rear M/cyl but the pedal was hard and I could tell the rears required more pressure so I went to 5/8.

I have found in my experiance that 7/8 M/cyl without a booster is a waist of time.
If you have no booster you go as small in the masters as you can.
I never calculate the areas ect I go by feel ,I always start 5/8 front 3/4 rear.
Some may not agree with my method but it works for me.

The rear calipers are 38 X 4 pistons in total
front 41 X 4 in total if you want to do the math.

Jim

 

[Grant]

Thanks for all your posts, for now I have rebuilt the servo and wet n dry'd the reaction piston as I'm pretty sure this was the problem area.

Fitted it back in the car last night and blead the brakes and they do now seem to be releasing OK.

I don't have an MOT yet so testing on the road will be limited until then, hopefully next week.

 

[Frank Catt]

I am surprised ( maybe not ! ) that no one has considered what makes the servo s work. It is essential to measure the amount of vacuum your engine is creating to operate the servos, this amount varies greatly depending on the configuration of the engine, and will have a significant effect on the performance of the servos / brakes. FRANK

 

[Jim Cowden]

Frank I am even more surprised (maybe not) you wouldn't use a vacuum reservoir if you had a big cam.

Im just being a smart arse Frank

Jim

 

[Frank Catt]

Jim, measure vacuum pressure ( negative ) not volume ! Frank