Caliper condition opinions

[neilbardsley]

Can you explain what different angles the pistons can be set at?

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[deano]

Another pic, shows the piston angle more clearly (marked in red) in relation to the brake pipe connection and caliper mounts... this is the rear right caliper.

[911hillclimber]

iirc the Haynes manual gives good details on the piston angle. There was a thread last year about this.
My M type calipers (stock M caliper, 73T) have anti squeal shims than sit into the angled slot so between the piston and brake backing plate.

[neilbardsley]

Ok so the angle is the rotation of the piston not the angle between the piston and the brake pad

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[deano]

yes, rotation angle of piston

I saw that some seal kits and piston+seal kits have some kind of steel shim, but I didn't know at the time what it was for, and my calipers never had them fitted. Yes, Haynes manual was on-hand too. All makes sense, once you know how

https://www.ebay.co.uk/itm/283785845145 ... BMkJGvv-ti

[911hillclimber]

There is a good illustration in the Haynes 911
manual to where to set the angle in the pistons.

[deano]

Now that the caliper is rebuilt (still minus two bolts, a 65 and a 70 mm, to hold the caliper together -can anyone help with these?), and new brake pipe section has arrived from D911, its time to put it back on the car and get the brakes bled and working again (with a new master cylinder).

I've never installed a brake pipe in my life - dumb question: do I need to use thread lock or PTFE tape on the brake pipe connections?

Another question about the caliper installation: the brake disc is still on - if I measure the disc thickness and fit the pads with a slightly wider gap using piston spreader, can I install the caliper fully assembled with the pads fitted? Or does it have to be disc off, pads out, first?

Last question, about the pads: they both seem to be quite new but thicker at one end than the other - is this normal/OK, or do I need to bin them and get new?

Please educate me with your kind wisdom!

Thank you! Dean

[911hillclimber]

So here goes, my thoughts based on about 20 full brake bleeds on my 73T:
1
The pipe will screw straight in, no need for sealents etc as long as they are all flared correctly at the end. This is CRITICAL!
Everything needs to be clean of course, the shape of the flare on the copper pipe end does all the work sealing.
2
Easiest is to install the caliper over the disc without the pads. Then ease the pistons back into fully retracted position one side at a time and pop the pad into place, then repeat on the other side of the same caliper.
Some might smear some Coppa-Slip grease on the steel backing plate to help stop squealing when using the brakes, this can occur. I've never bothered.
Install the retaining pins and R clips. Some retaining pin designs are different to others, but obviously need to be in place.
When all done gently press the brake pedal to bring the pads to the disc ready for the 'thrill/adventure/test of patience bleeding...
3
Best to fit new pads. They should be even thickness new and when worn. If you have assembled the pistons correctly the pads will wear without generating a taper of the brake material.

Bleeding can be a real pain, start farthest away, ie the rear caliper with the longest pipe run, but both rear runs are much the same length, the fronts are different, so be sure you finish the bleed cycle with the front with the shortest pipe length, so it will be the one closest to the master cylinder.
Don't be concerned if the first round of bleeding is disappointing, ie soft long travel, just keep on at it and it will come right. You will use a lot of fluid before you are done.
The master cylinder reservoir is not large so will empty quite quickly when bleeding, so check the level frequently as you go round, ie after every caliper 'visit'.

imho, only use ordinary brake fluid for a road car, fancy stuff is a waste of money.
I have found when bleeding any car from 'empty' to gently tap the caliper you are bleeding with a plastic head hammer to encourage any air bubbles free inside the caliper to make their way out.
Over the many years of this caper I have found my wife is the perfect partner to bleed the brakes on anything, she is highly trained and very experienced now, but the available pressure or suction devices to aide bleeding are effective too if used carefully to avoid any fluid spill.

Finally, once you are happy with the pedal feel etc leave it all to rest overnight or a day and check again, a good hard push on the pedal will show a good pedal or you still have some bleeding to do.
Any improvement by pumping the pedal also shows more bleeding is required.

Hope this helps.

[deano]

More than helpful, thank you!

Will get some pads ordered....

Any possibility of getting your wife to come and help me then? I'm sure we are only round the corner from each other

[911hillclimber]

I've seen her invoices for this specialized work...
Her eyes usually roll when I start to mention bleeding the 911 brakes, the Lola's are a snip by comparison yet more complex.

[Nine One One]

Also remember if you use a pressure system to bleed the brakes like 'Easi Bleed’ - There is an overflow/vent plastic pipe to the right hand side of the master cylinder reservoir, and you need to plug this, otherwise, as many have found, you fill your front trunk with brake fluid and it then pi55es out all over your garage floor!

[911hillclimber]

Doesn't it just!
Reeked havoc in my car many years ago, hence Mrs Hillclimber being recruited.
Had it pass fluid via the cap too, never again but I did apply 20 psi via the spare wheel.

[MikeB]

Like others I have learnt about too much pressure when using EasiBleed. I use about 12 psi in a tyre and to blank off the vent on the Porsche reservoir I used a 40 mm long piece of small bore Screen washer tubing, sealing one end with a bit of fire (eg a lit match) and then heated the other end with a hair dryer so it became pliant and would push over the barbs of the vent tube and then shrink over it, so it doesn’t blow off under pressure