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Joined: Jan 03 2020
Posts: 111

Hi guys,

It looks like I'll be following my front axle refurb with a rear axle one.... what fun!

A quick glance at the rear brake lines tonight showed lots of very, very rusty connectors and hose ends - and quite complicated routing, which (at first sight) I don't fully see the point of.

When I did my Defender recently, I went for a full set of braided, stainless lines for the entire system. Should never need to look at them again.

So I'm wondering about a set of these for the back of my P38. I don't know what the cost might be yet ( I need to take some measurements first and send these and some pics to the supplier so he can make up a quote). The full Defender system was ca. £300/350 I think.

If I did this, then I could go for a much simpler routing. I suppose it would be possible to simply run a long, single hose from the ABS unit to each caliper, allowing enough length for axle flex and articulation. More likely I'd opt to have a join in them somewhere. As they are stainless fixings there isn't much concern about future maintenance.

I did a search for braided lines and didn't find anything, so my apologies if this is an old chestnut.

So, has anyone done this? Are there routing issues to consider? Why do the lines run up from the chassis to the top of the rear shocks... and then over the tank.. ? Is there any reason a much simpler/more direct route can't be used?

Even if there is a reasonable expense involved, apart from longevity, not having to deal with awkward joins and routing would probably be worth paying for in my opinion, and would doubtless avoid lots of stress and swearing.

As always, any advice or comments gratefully received.

Thanks.

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Joined: Dec 30 2015
Posts: 5064

Braided brake hose kits are available, https://www.merlinmotorsport.co.uk/s/goodridge/goodridge-brake-hose-kits/brake-hose-kits-car/range-rover or, if you wanted to go the whole hog and replace the full lengths with braided, just buy the hose and end fittings https://www.merlinmotorsport.co.uk/s/goodridge/goodridge-600-series-brake-clutch-hose-fittings and make them up yourself (although not sure you'd be able to get the end fittings for the callipers with the strange lump on the end to stop them from being able to twist). I've got a 1990 Maserati Biturbo Spyder and the hoses for that are NLA so bought the hose and fittings and made them up. A lot easier than I thought it would be.

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Joined: Jan 03 2020
Posts: 111

Thanks very much. I hadn't considered that pre-made kits might be available - or even DIY!

As soon as you mentioned the caliper-end fitting I thought 'of course!' - it is indeed a strange lump. It's obvious what it does, but I wonder if it's essential? The Defender doesn't have those - though I'm not suggesting it's the last word in technological advances!

Have you any thoughts about routing? Any obstacle to simpler, or more direct line runs?

Thanks

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Joined: Dec 30 2015
Posts: 5064

The existing pipes run down the RH side of the car so one of them has to get over to the other side at least. I assume running them in before the tank was fitted was easier when they were building the car. The routing on the early cars was even stranger with a pair of hoses in the centre between the body and the rear diff then pipes running along the axle. If you are making up your own lines then where you run them is up to you. That's what has been done on most cars now where the long runs have rotted so Kunifer has been run between point A and point B with various routings in between. Before you ask, the fittings are all Metric.

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Joined: Sep 14 2016
Posts: 518

From an engineering viewpoint the early car hose routing basically follows a common practice for a beam axle rear suspension car. Hard pipe down the vehicle, intermediate flexi to an axle mount to take suspension articulation, hard pipe across the axle and short flexi to each calliper so you can service brake pads et al without disturbing connections.

Sensible if you only have one front to back line as in pre ABS days. At best inelegant when you have independent lines to each calliper.

Basic routing on the later cars is much more logical with independent hard pipe to calliper routing on each side with a single body side cross pipe. The hard pipe ends at a body mounted bracket with with the short flexi jump hoses going to the first chassis mounted bracket. Presumably these cover any possible movement between body and chassis.

Surely they can’t move that much?

Even if there is movement to handle the extra flexi and short hard pipe each side seem way overkill. Far as I can see there is no reason why the hard pipe couldn't run down onto the chassis or onto a longer body mount bracket close by and pick up a longer flexi from the calliper. Maybe an intermediate fixing for a clip to hold the longer flexi in the right run.

If I were to modify the system thats what I'd do, Kunifer down to a re-engineered version of the body bracket then braided stainless covered hose to the calliper. The braided hose would be rather longer than the standard flexi one, which seems quite short given the amount of suspension articulation it needs to cover. Or maybe ignore any possible body to chassis movement issues and do an "inverted" version of the lower jump hose bracket and pick up there. Inverted to give more spanner swing room. But still need something to tie the ABS wheel sensor cable too. Bulkhead fittings on the bracket of course. I’d rather poke Kunifer all the way up a car than braided flexi.

The anti rotation "banjo with a lump" fitting on the calliper is needed because there is only a short length of hose between the calliper banjo and the first clamp. Low end mechanics don’t unbolt hose clamps! Without the lump it would be easy for low end mechanics twist the banjo loose when removing the calliper. If you have a loose guide rather than tight clamp there is no problem.

I’m usually not shy about modifying things but elected to keep mine standard due to not understanding why things were done that way. To me the P38 falls into the same category as Soviet weapons systems in that there is usually a very good reason for “WTF did they do that!” so jumping in and changing for something apparently more logical can dump you in a world of grief.

The only reason I can think of for all the flexi pipes is to control ABS and ETC resonance effects There seems to be fairly extensive literature and respectable number of patents floating around this subject. Sharp hydraulic fluctuations can resonate up to very high localised pressures if there is no damping in the lines. Flexi pipes will provide damping, even without expansion.

The big weakness of braided hoses is that the join between hose and fitting is relatively weak in tension. The crush collet doesn’t get a particularly good grip on the slippery teflon core. It’s frequently quite easy to simply pull the hose out by hand. Especially when home made.

Clive

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Joined: Jan 16 2016
Posts: 425

I fitted Goodridge braided hoses all round over 10 years ago from one of their outlets in Stockport, Cheshire.
Mine are +2" and I remember they had the patterns on record which saves taking measurements and thread sizes etc.
I also remember a choice of just the hoses alone or inc stainless fittings. I went with the latter and it pushed the price up quite a bit.

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Joined: Jan 03 2020
Posts: 111

Thanks very much again.

Lots of food for thought there. While I have a practical eye, and can anticipate and consider basic things like axle articulation, I have to say it wouldn't even have entered my head to think about ABS or TC pulse resonance.

I think, when I come to strip down the back axle, I'll end up having to use the same wire brush + hammer and chisel + power tool brushes approach to deal with all the rust as I did with the front; not to mention the subsequent coats of rust converter, paint and underseal.

So I expect to have enough time, and better access, to have a good look at it all and consider what combination of flexi or kunifer makes sense; if/where to incorporate joins and how to route the lines. I already know from removing the EAS reservoir that there are additional joins in the existing copper lengths, so one of the motivations is just to simplify and improve while I'll have the system drained anyway.

I had a closer look at the DIY system GilbertD linked to above - quite surprising in its simplicity and something to think about - though I note the point about potential weakness in tension.

The only thing that's not in doubt is that I'll need to do 'something' - the state of the current system doesn't inspire much confidence.

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Joined: Dec 30 2015
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Originally there was a pair of connectors next to the bulkhead lower down before the pipes connect to the long ones that run to the back of the car. They can be seen easily with the RH front inner wheelarch liner out. They are the only joins that should be there. After that they are clipped to the underside before disappearing above the fuel tank and various other bits and pieces. There's a good diagram of where they run in RAVE even though it is wrong and shows a pic of a RHD car but says it is for LHD and vice versa.

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Joined: Dec 30 2015
Posts: 2028

I'm no expert but I avoid braided lines after a series of failures affected the Fiat Coupe community a good few years ago. Maybe it was a bad batch from Goodridge or maybe it was because it's hard to inspect the rubber lines under the pretty stainless - maybe we just got unlucky with the resonance effects that Clive brought up. I guess we'll never know.
If you keep on top of standard flexi lines you've a good chance of replacing them when they're weak.

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Joined: Dec 30 2015
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If they were rubber under the stainless, then they were cheap, pretty, replacements. The genuine Goodridge is PTFE tube so the only thing that can fail is the connections to the ends.

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Joined: Dec 30 2015
Posts: 2028

They were Genuine Goodridge and they failed - more than one set. If it was PTFE then it was the PTFE that failed. Like I say, it could have been a bad batch but it was a very close call in some cases.

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Joined: Jan 16 2016
Posts: 425

Hmm ........ maybe I should carry a boat anchor with me to throw out of the window ....... just in case.

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Joined: Jan 03 2020
Posts: 111

I believe there is one, not insignificant, downside to braided lines - that you're not supposed to clamp them shut for maintenance purposes as this can damage the ptfe liner. I wonder if this could be behind some failures? Folk being unfamiliar with this aspect of them, perhaps especially when they started to become more widely available and used?