Brake pipes tweakery stuff.. - Alfa Romeo Forum
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Brake pipes tweakery stuff..

The long version:

Tarquini's rear brakes are not good enough for Doctor Death to give the beast a MOT so I'm gradually changing everything until they give me the magical 130kg of effort neeed. MOT test only showed 60kg so even though it felt okay and stopped okay, obviously it wasn't actually okay.

As part of my attempts to get the beast up to muster, I fitted a new compensator valve (+20kg) new pads and handbrake cables (separate "Advisories") and finally new calipers (+20kg). I'm only at 100kg.. so still waaay off, though miles better than before.

The good Doctor did notice that some of the metal pipes were twisted however and reckoned this could be the cause.. (if they became internally impeded) though to be fair he's quite sceptical and puzzled because the compensator and calipers should have done it.

The brakes bleed okay.. lots of fluid comes out and not much effort required, so that would suggest the pipes are fine. Also, the brakes "have always been ****" according to the Doctor... it's always a borderline pass and has been for the last 4 or 5 years.

Anyway.. there's not much left to change and pipery is just a few quid after the bigger items above, so I decided I'll change them anyway. I already have steel braided hoses on the calipers and it could be that any twisting happened when I fitted those...

I ordered up the pipes from Mr Romeo .. 4 to/from the rear brake compensator and one on each trailing arm, so 6 altogether. I also got new flexible pipes for the trailing arm pivot.

However, AR's parts supply for such an old beast is not toooooo good and of the 6 metal pipes, only 2 are still available, so I'll need to make the others. Go to "The short version".

The short version:

I had a look at what sort of brake pipe tubing is available.

I think I need 3/16" (5mm) tube... seems to be about the right size and the most common?

I also think the unions are "10mm" males, though there are also two larger ("12mm"?) unions on the pipes to the brake compensator (2x10mm, 2x12mm) as when I changed the compensator I remember 2 of the unions were a bigger size than the other two.

Is that right?

Does the 10mm/12mm for the unions refers to the nut size or the thread diameter? I remember using an 11mm brake spanner when I did the compensator

Also.. what's better or what's the pro's and con's of using copper or that Kunifer doodah? Kunifer sounds a bit more like the kind of gig I want to go to (cupro-nickel rather than just copper) but is it fantastique or does it have other issues that make it inferior to copper in some/any way?

I can buy the flaring tool and a bender once I have all the bits and pieces I need. I never made my own pipes before so could be interesting... and any tips will be useful.

Ta.

Ralf S.

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The advantage of Kunifer is that it doesn't work-harden like copper, which means that it won't tend to crack if subjected to vibration.

What concerns me here is that I can't see how you're going to get more braking effort by replacing pipes. If the system is bleeding properly there are no significant blockages, so you will be getting full system pressure at the wheel cylinders.
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Aye! That's what I think.. but I dunno why the brakes are otherwise so weedy now.

The fronts are pokey enough but the rears seem to be just weak and have been for ages (albeit not so bad to fail the MOT in the past.. but there wasn't much in it).

The 145 I'm driving about in has more or less the same braking system and that feels a lot sharper on the brakes, particularly the handbrake, so something is different back there.

My only other idea is that the master cylinder or the servo may be a bit duff but the front brakes are good. The system feels more spongey than the 145 one but I bled it a million times and I think it's as bled as it can be.


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I've been following your posts on this with great interest - wish I could add something positive. How are the circuits split? I assume diagonally, in which case a master cylinder or servo problem should show as low effort on opposite corners, not front to rear.
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Aye! There's a diagonal switch-over in the brake compensator.

The rear brakes both have the same amount of braking force as each other.. bang on 60kg before and both bang on 100kg now. The handbrake is also a bit marginal despite the new (recon'd) calipers, cables and pads.. so it's barking mad and even Dr Death (aka Matey Mechanic) doesn't know what to suggest. The "brake pipes" is sort of clutching at straws really and he admits it.

Anyways, the pipes aren't great anyway and not a huge expense so I decided to change them anyway as it's not going to make things worse and I'm not off the road any more (c/o 145). It's just a puzzle.


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Does anyone know the answer to "The short version" above?

Do I needs 3/16" pipery or is the beast 5mm metric? So far it seems that the Kunifer pipes have the edge on regular copper...

What about the fittings. 10mm/12mm? Anyone know?

Ta.


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Do the numbers get better if you load the rear with extra mass? Also I don't know if it is available in brake line sizes, but there is an alloy called Tungum which has excellent anti-corrosion properties and was/is used in aircraft hydraulic systems. The Wellington at Brooklands which spent a great deal of time under the water, (Loch Ness) had pipes made from Tungum and they were in very good condition after all that time.
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Tungum...?

I'll have a look for it... just need to know the size of the standard AR brake pipe.

The Doctor tried adjusting the compensator spring tension and the readings went a bit feeble after he loosened it off (he thought it might be over-tensioned and I humored him... ). So it looks like I need the equivalant of more tension on the compensator rather than less (what I thought anyway) and adding more tension/load does give a higher reading.

My spring is a mongrel from the depths of the garage so I also bought a genoooine AR pedigree spring.... just to eliminate the spring as the source of the problem.. just I haven't fitted it yet, pending the brake pipes etc. which I decided I'll change regardless, now.


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Last edited by Ralf S.; 16-01-10 at 11:11.
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Tungum Alloy:

Aluminium, Nickel, Silicon and Brass ... combines an unusually high strength to weight ratio, with ductility, excellent corrosion resistance and first class fatigue properties. Highly resistant to sea water and its atmosphere, Tungum resists both stress and crevice corrosion to offer outstanding serviceability. Non-magnetic and non-sparking properties make Tungum invaluable in piping high pressure gases, particularly oxygen where its thermal conductivity/defusivity characteristics virtually eliminate the potential dangers present when lesser materials are employed.



I gotta get me one of those!


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I gotta get me one of those!
Ain't gonna be cheap!
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Imagine if thw whole car was made of it!



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