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Girling Hydraulic Brakes

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clevitt
Posts: 184
Joined: Wed May 18, 2016 1:02 pm
Location: West Hertfordshire

Girling Hydraulic Brakes

Post by clevitt »

My query relates to the front hydraulic wheel cylinders on the DB18 Barker SS, but I believe that the same Hydro- Mechanical system is common to other models. Whilst overhauling the front brakes I have noticed a difference in the left and right sided Expander ( Brake Plunger) units when the brake shoes are fully retracted i.e. brakes are off. The first photo is the right (offside) unit, note that the plunger face is flush with its housing, whereas in the second photo ( nearside) it sits about 1/4 inch below.
IMG_1278 (2).JPG
IMG_1272 (2).JPG
I think that the nearside is correct because I have noticed that on the offside the brakes do not fully release but feel like they are catching on high spots on the shoes. I believe that this due to the movement of seal behind the piston being constrained to the bottom of the cylinder. This is just a theory and I'm happy to be corrected.
The Plunger Housings do have a part number stamped on the underside and, although they do not conform to the Component List numbers, they are simillarly different by one digit , so I think that I have the correct assembly for each side. The Component List indicates that both first and second shoe Tappets are sided, so are either or both Tappets incorrect for the offside? Does anybody have access to Girling documentation that shows the difference between the two sides?
Chris

Peter Grant
Wise Man
Wise Man
Posts: 503
Joined: Thu Mar 10, 2016 10:02 pm
Location: Sydney, Australia

Re: Girling Hydraulic Brakes

Post by Peter Grant »

Hi Chris,

While I cannot help you with the specific question you pose, I can relate my recent experience with my own Special Sports.

People who had driven my car had commented over the years that the brakes were awful.

I guess i had just put up with what I thought were old design and quirky brakes and just applied the right dorsiflexor with force when required.

Recently when I took the car in to a new mechanic for a 70th birthday present overhaul (the car, not me), the mechanic found that the brake cylinders were all seized up so they were dismantled and thoroughly cleaned, then the hydraulic brake hoses were found to be collapsing inside so impeding the proper ebb and flow of brake fluid to the cylinders.

So after the thorough cleaning and reassembly and all brake hoses replaced the pedal pressure required is much less and my car doesn't "jump to the right" during a sharp stop at traffic lights!

You have probably done all this work already or had planned to di it, but just in case....

Cheers
Peter Grant

clevitt
Posts: 184
Joined: Wed May 18, 2016 1:02 pm
Location: West Hertfordshire

Re: Girling Hydraulic Brakes

Post by clevitt »

Thanks Peter, replacing the brake hoses was part of the overhaul plans whilst the system was drained due to the bi-annual fluid change. Every two years, I ask myself if this really needs to be done so frequently :?:
Yesterday, I set the brakes up from scratch and both sides are now sitting with their plungers about 1/8 inch below flush. I can operate the shoes manually by pressing the plunger with my thumb and the shoes retract without sticking. I may still have a problem with the hydraulics, because the wheel cylinders have been resleeved, and I can see a small gap between the bottom of the new sleeve and the bottom of the cylinder. This gap is enough to catch the brass former for the seal and hold it against the spring tension. I think this is the cause of the stickiness when the brakes shoes come off. I am contemplating shortening the cylinder's pistons to ensure that the seal and its former always operate above this gap. Is there any downside to reducing their length: I am thinking about removing 200 thou from the existing 1 inch length?
Looking forward to any comments from all those wise men and gurus on the forum.
Chris

Db n j
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Posts: 919
Joined: Sun Mar 13, 2016 8:55 am
Location: uk shropshire

Re: Girling Hydraulic Brakes

Post by Db n j »

Chris, i am following with interest, as I will be doing same with our barker soon.

Can you tell me who did the sleeves , as all the cylinders I have look poor, as do the pistons.

Thanks

Db

clevitt
Posts: 184
Joined: Wed May 18, 2016 1:02 pm
Location: West Hertfordshire

Re: Girling Hydraulic Brakes

Post by clevitt »

Hi David, I only finished installing the new flexible hoses this morning: the high pressure hose ( from master cylinder to fixed copper ) is a real b....r due to very difficult access for open ended spanners. Should be a two man job, one on the floor and one working from above. The wheel cylinders were done by Past Parts at £50 + VAT each (2015 prices) . I’ve no issue with the quality of their work- I think my issues are due to the dynamics of the car’s braking system. Plan is to bleed the new fluid tomorrow, after which I’ll know if I have any residual problem and therefore need to shorten the pistons.
Chris

Db n j
Wise Man
Wise Man
Posts: 919
Joined: Sun Mar 13, 2016 8:55 am
Location: uk shropshire

Re: Girling Hydraulic Brakes

Post by Db n j »

Thanks Chris.

Just had a chat to Past Parts, very helpful and knowledgable.

Cylinders sleeved for £45 plus vat.

Shoes relined at approx £25 plus vat per shoe.

( only riveted shoes not bonded can be taken)

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