First off, note that for many years braided hoses were not approved for road use by the DOT here in the US. This was for several good reasons, including the fact that metal braid will not contain fluid but will prevent inspection of the materials that do contain fluid. Reportedly the only braided hose available that is now DOT approved consists of a Teflon tube surrounded by the braid. The Teflon is the entire pressure containment of this assembly; the braid provides no value to holding pressure, since it doesn't even fit the Teflon tube that closely. The Teflon tube, in fact, appears rather similar to the tube in the center of the OEM rubber hose, except the tube within the OEM rubber hose is smaller.
At one time, Teflon tubing was tried -- without braiding around it -- as brake lines in race cars. Not for just the hoses, mind you, but in place of the metal brake lines throughout the entire car. It weighed less, and you could actually see the fluid inside and whether or not there were bubbles in it. It was soon discovered, though, that a stone impact could shatter this tubing and cause a brake failure, and such brake lines were promptly prohibited.
So we see the purpose of the stainless steel braid: it's there to protect the Teflon tubing from physical damage. That's all it does. And, in fact, that's the same thing the rubber does on the OEM hoses.
Besides the fundamental differences between the rubber hoses and the braided hoses, there are also many issues evolving from getting "aftermarket" hoses to fit properly. For example, some aftermarket stainless steel braided brake hoses come with #4 AN fittings at both ends and adapter fittings must be used to connect such hoses to the calipers and lines in a Jaguar.
Obviously, this adds another connection and hence another potential point of failure or leakage. Fortunately, AN fittings are quite reliable, so this isn't a serious concern.
Also note that the adapters are rarely made of stainless steel. In fact, the nut on the hose itself in this picture is not stainless steel. If you were hoping for something that would look bright and shiny for a long time, you will need to keep shopping.
The bigger concern, though, is that the adapters are actually correct. The fitting on the end of the Girling hose in the picture, which is the original rear brake hose from Kirby Palm's 1983 XJ-S, is 10mm x 1.0. The adapter in the photo is unmarked but measurements show it is a #4 - #3 AN "bulkhead" fitting. "AN" stands for Army-Navy; this standard is also called JIC for Joint Industrial Conference. 10mm x 1.0 is not the same as #3 AN. The thread on #3 AN is 3/8"-24, or standard 3/8" UNF. Needless to say, you do not want to mismatch threads on a brake system. Check very carefully, as these two are close enough you can actually screw them together.
If you want to make absolutely, positively certain that your car requires metric fittings, get under the car and check the wrench size for the nut that screws onto the fittings. If it is 13mm, it is metric; if it is 1/2", it is AN. In other words, if a 1/2" open-end wrench will fit on the nut, it's AN; if it won't, it's metric.
It is possible to get metric fittings:
The adapter at the left is basically the same thing as the one in the picture at the top of the page; it is unknown why this one is a yellow color. The one on the right is a 10mm thread, the correct thread for the XJ-S. However, it is not a bulkhead fitting, which means it cannot be used to install a brake hose the same way the original hose was installed.
That may be just as well; it would probably be a good idea to mount the braided hose differently anyway. Here's why: The braided hose in the photo above is attached to the fitting at the end by being slid onto a barb and a separate sleeve is crimped down onto the braid. As a result, the weight and stress of supporting the hose is applied to the barb itself. You need to be concerned about the hose "blowing off" and the possibility of it getting "pulled off" -- say, if you run over a stick and the tire pulls the stick through the wheel well. You also need to be concerned about the barb breaking off, since these barbs are pretty thin and spindly and the hoses get subjected to a lot of tugging and pulling as the suspension moves.
With the OEM hose, the crimped sleeve isn't separate -- the sleeve is part of the fitting itself. When assembled, the sleeve provides mechanical strength to the attachment. As you can see in the picture at the top of this page, it appears very secure indeed; if you pulled hard enough to rip it apart, the hose itself would probably tear before that connection would come loose.
The original hose mounting scheme -- mounting by the bulkhead fittings at both ends -- relies on that crimped connection to hold the hose. The same mounting scheme should not be considered acceptable for supporting the aftermarket hose shown in the picture above. A braided brake hose with such connections at the ends should be physically supported by providing support straps around the hose itself to take all the load off the fittings.
The ports where the hard lines connect to the inboard rear calipers themselves are 3/8"-24. Hence the hard lines from the hose to the calipers are metric threads on one end and 3/8" threads on the other. Don't you just love the British? Whatever, this opens more possibilities: you can replace the hard lines from the hose to the calipers with lines that have 3/8"-24 threads on both ends and then use the #4-#3 AN bulkhead fitting shown in the photos above on that end of the hose. You'll still need a metric adapter on the other end, unless you replace those hard lines too.
Another possibility is ordering a longer hose and eliminating one hard line entirely and connecting the hose directly to a tee at the top center of the rear subframe. Perhaps workable, but most of us would rather keep flex hoses as short as possible since they add mushiness to the pedal feel.
The connections where the short hard jumper lines connect to the front
calipers are metric. Don't you just love the British? The bleed
screws are the same way: metric at the front, Imperial at the rear.
A note about length: The rear of the Jaguar XJ-S with inboard rear brakes uses a hose that is 10" long from point to point and has metric fittings on both ends. This is not the same as the XJ saloons, which require a longer hose.
With the original hoses, it makes sense to measure from point to point. If you're ordering aftermarket braided hoses, remember that if they use bulkhead adapters the adapters add about 3" to the overall length, so to end up with a 10" assembly for the rear of the XJ-S you'd need to ask for a 7" hose. Getting a 10" hose and then adding adapters will not fit, you'll be bending hard lines to try to get it to work.
Walter Acker IV found a place that will provide custom-made teflon hoses with stainless steel braid with the correct fittings right on the hose -- no adapters necessary:
OEM brake hoses come with a stripe down the side. This is to make
it easy to be sure that you haven't twisted the hose during assembly.
The SS braided hoses don't have any such stripe, perhaps because twisting
isn't the problem it is with a rubber hose (they are much more difficult to
twist) or perhaps because twisting won't damage them -- or perhaps because
you can stare closely at the braiding pattern and figure out if it is twisted.
Whatever, if you want to make sure they're not twisted, you can just draw
a stripe down one side with a magic marker. Since you have an extra
AN connection at each end, it is a rather simple matter to install the adapters
tightly and then the hose loosely, and tighten the AN nuts while making sure
the hose doesn't turn.
Take a bit of advice: forget all this garbage about how to install braided
brake hoses and just get a new set of OEM rubber hoses. They are, in
fact, the best hoses for the job, and the sooner you accept that fact the
safer you're likely to be.
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