Brake lines-minimum bend radius?

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ndevans
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Re: Brake lines-minimum bend radius?

Post by ndevans »

Hello hive mind. What is the opinion on the bend of this pipe? This is the feed from the master cylinder to the servo, in the engine bay. It isn't the original factory fitted pipe, I replaced it 5 years ago, when I fitted the servo and discs.
Also, which way should it be routed? I have it going through the semi-circular hole in the centre cross member, next to the chassis rail. Should it loop over the cross member? How does it get past the clutch mechanism? The diagram on page M2 of the BMC manual seems to show it going over the cross member, but it's not very clear.

The reason I ask is because I'm not happy with how I routed the pipe. As you can see, in the second photo, it's a bit too close to the clutch mechanism for comfort.
Cheers N
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cheers N

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les
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Re: Brake lines-minimum bend radius?

Post by les »

I’m pretty sure it should be above the crossmember, one reason being it doesn’t then prevent crossmember removal, if needed. Originally, in places where the brake pipe goes through restricted spaces there was a few inches of split rubber sleeve fitted around it, for protection. The route your pipe takes doesn’t look right to me. I personally like brake lines to run close to bodywork and where possible clipped, as opposed to running unsupported.

philthehill
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Re: Brake lines-minimum bend radius?

Post by philthehill »

The brake pipe should go above the cross member and as Les says it should be sheathed in a split rubber sleeve to protect from chaffing.
See picture below.
brake 1.jpg
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ndevans
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Re: Brake lines-minimum bend radius?

Post by ndevans »

Ta. I thought it was best that way. I routed it through the cross member when I fitted the servo, but I've never been happy with the tight radius curve, and of course moving the cross member is more difficult. I've now got a new piece of Kunifer pipe in place, ready to cut the end to length and get flares put on.
Cheers N
cheers N

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ndevans
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Re: Brake lines-minimum bend radius?

Post by ndevans »

philthehill wrote: Sun Feb 16, 2020 7:25 pm The brake pipe should go above the cross member and as Les says it should be sheathed in a split rubber sleeve to protect from chaffing.
See picture below.

brake 1.jpg
Phil, have you got a servo fitted as well? There seems to be two pipes going over the cross member.

Cheers N
cheers N

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philthehill
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Re: Brake lines-minimum bend radius?

Post by philthehill »

The photo is not of my car but put up to show how the brake pipes should be fitted over the top of the cross member and enclosed in the split rubber sheaving. The second pipe I suspect is to connect with the servo.
Phil

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ndevans
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Re: Brake lines-minimum bend radius?

Post by ndevans »

Is it ok to re-use brake lines? The ones across the back axle are about 5 years old, copper, and look good. No obvious sign of stressing or cracking, the flares look good as well.
Cheers N
cheers N

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oliver90owner
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Re: Brake lines-minimum bend radius?

Post by oliver90owner »

Is it ok to re-use brake lines?

I have never replaced brake lines ‘just because they are 5 years old’. I go on condition - that includes corrosion, material, condition of contacting parts and any other points which may be appropriate.

They are a safety item, so should be in perfectly usable condition. I don’t think anyone would give you a definitive answer on your particular lines from a distance. Put simply - if in doubt, throw them out.
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ndevans
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Re: Brake lines-minimum bend radius?

Post by ndevans »

I have made up new Kunifer pipes from the master cylinder to the servo, front 3 way union to rear flexible hose and the two pieces across the back axle. These last two were copper, the others were Kunifer, but I wasn't happy with the routing. All my brake lines are now Kunifer.
In other news, after a conversation with a lady from Automec, who supplied the old back axle lines, I now know how to identify copper brake line. If it's 4.76mm o/d (3/16"), the wall thickness will be 0.9mm, and it should say so. Mine are marked 4.76mm x 0.9mm, and 3/16 x 20G, the G meaning 20swg, which is 0.91 mm. Kunifer lines will be marked 4.76mm x 0.71mm, and 3/16 x 22G, 22swg being 0.711 mm.
I checked both my old back axle lines and the new length of Kunifer pipe, and sure enough, they are marked as above.

Cheers N
cheers N

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ndevans
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Re: Brake lines-minimum bend radius?

Post by ndevans »

Final position of the new line from the master cylinder......
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..... And the new route between the clutch pedal. Compare with the photos I put up earlier in the thread, it's much better.
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I still have to get flares put on, so this is not the final fitting. I will put a length of old rubber hose over the pipes where they cross the cross member. In the clutch pedal photo, the master cylinder-servo line is tucked up under the clutch pedal shaft, the line from front 3 way to rear flexible hose is on the left.
cheers N

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philthehill
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Re: Brake lines-minimum bend radius?

Post by philthehill »

Re your picture of the pipe from the master cylinder:-

Make sure that the pipe is straight for at least an inch from where it exits the union nut before curving up and over the cross member. If it is not straight it can lead to stress and ultimate fracture/failure.

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ndevans
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Re: Brake lines-minimum bend radius?

Post by ndevans »

philthehill wrote: Thu Feb 20, 2020 7:53 am Re your picture of the pipe from the master cylinder:-

Make sure that the pipe is straight for at least an inch from where it exits the union nut before curving up and over the cross member. If it is not straight it can lead to stress and ultimate fracture/failure.
Ok, noted, will do. Thanks.
cheers N

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philthehill
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Re: Brake lines-minimum bend radius?

Post by philthehill »

Just invested in one of these

https://www.ebay.co.uk/itm/US-PRO-Pipe- ... 2749.l2649

Arrived today and I have already tried it on some 3/16" Kunifer brake pipe and it makes a nice job of bending the pipe without deformation at a 18mm radius.

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ndevans
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Re: Brake lines-minimum bend radius?

Post by ndevans »

Hello again all.
Got the flares done by a local friendly garage. However, not too sure about a coupe of them. There is a bit of a ridge where the die blocks meet. What's the view? Are these useable? I'm a bit reticent to go back, as the guy did it while his boss wasn't looking, and I'm not sure I can push my luck too far! Cheers N
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cheers N

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philthehill
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Re: Brake lines-minimum bend radius?

Post by philthehill »

Those flares is no good and I for one would not trust them. The flare should be smooth all round with no ridges or imperfections.

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ndevans
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Re: Brake lines-minimum bend radius?

Post by ndevans »

Thought not, thanks for confirming. I guess I can't file the imperfections out?

Cheers N
cheers N

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philthehill
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Re: Brake lines-minimum bend radius?

Post by philthehill »

I would suggest that you do not smooth out the imperfections. There may be a stress fault/crack under the imperfections.
Not worth the risk - get new flares fitted to the pipe.

I would also suggest that the flaring tool anvils are worn or the anvils were not tightened sufficiently in the tool.

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ndevans
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Re: Brake lines-minimum bend radius?

Post by ndevans »

Thanks.
I have a friend who used to be a service engineer for the RAC, he's going to do them for me.

Cheers N
cheers N

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ndevans
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Re: Brake lines-minimum bend radius?

Post by ndevans »

Slow progress. I have new flares on the master cylinder-servo pipe and the front 3 way to rear hose pipe now, but still waiting the back axle pipes. While I'm waiting, I am fitting the two pipes I have ready.
Try as I might, even though I measured and bent the pipes to shape, I'm finding it really difficult to get a route for the pipes through the clutch pedal area. I don't seem to be able to avoid having them run between the pedal and gearbox, above the relay shaft. I have got them bent such that the pipes do not bind on the clutch pedal when it's fully depressed, but I'm still not happy. It doesn't seem right, as it means the pipes are unsuspended for about 15cm, which means they can vibrate.
I've tried routing them next to the chassis rail, under the clutch pedal shaft, but it didn't really work. Any suggestions?

Cheers N
cheers N

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oliver90owner
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Re: Brake lines-minimum bend radius?

Post by oliver90owner »

Longer pipes?
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