Stainless steel brake hoses.
It has been brought to my attention that some folks are confused about the difference between “DOT-approved” and “non-approved” stainless-steel brake lines. Despite the fact that this explanation is somewhat lengthy, I believe it will cover all of the bases.
To begin, a brief explanation of what stainless-steel brake hoses are and how they work:
When we talk about brake lines, we’re referring to the flexible ones that connect between the hard lines in the car and the brake calipers mounted on the wheels.
Traditional rubber tubing with steel or aluminum connections crimped onto the ends has been used to create these devices for decades. Rubber brake lines are standard equipment on nearly all passenger automobiles, and they are rarely if ever defective.
Lines labeled “stainless steel” are really constructed of Teflon tubing, not rubber. While rubber offers a variety of advantages over teflon, the two most significant are that it does not expand under pressure and does not degrade with age. It also withstands high temperatures and is chemically inert, allowing it to be used in conjunction with any brake fluid.
Teflon, on the other hand, is extremely fragile, and it must be safeguarded from physical harm. Despite the fact that some manufacturers armor their Teflon hoses with Kevlar, the majority of producers cover the Teflon with an exterior sheath of braided stainless-steel wire. Because of this, armored Teflon hose is commonly referred to as “stainless-steel hose.“
The ends of the hoses must be tightly attached to the brake calipers and hard lines, which is why each hose is ended with threaded hose-ends to provide a solid connection.
There are several methods in which those hose-end fittings can be connected to the hoses.
The cheapest method is to crimp or swage them onto the hoses, similar to how rubber hose fittings are attached. It is more expensive to employ a two-piece replaceable hose end that traps a section of the hose between an inner nipple and a concentric outer socket, but it is a more convenient method. This type of hose-end is found almost everywhere, including on aircraft and race cars, as well as in many other applications.
As a result, what is required for a stainless-steel brake line to be approved by the Department of Transportation?
First and foremost, I should note out that there may be lines available that match all of the DOT specifications, but are not approved simply because they have not been presented to the DOT for consideration.
Manufacturers cannot legally claim that their lines have been approved – even if they are certain that the lines fulfill all of the DOT criteria – unless they first submit the lines to the DOT for approval.
As a result, stainless-steel brake lines can be divided into three types: abrasion-resistant, corrosion-resistant, and heat-resistant.
“DOT authorized” – These lines have been submitted to and approved by the United States Department of Transportation.
Lines that are not approved by the Department of Transportation are either because they do not satisfy the specifications or simply because they have not been submitted for testing.
These lines are not approved because they do not comply with the Department of Transportation specifications.
The safety standard that brake hoses must fulfill is known as Federal Motor Vehicle Safety Standard 106, and it may be found in Title 49, Volume 5, Subpart B, Section 571.106 of the Code of Federal Regulations if you have a copy of the Code of Federal Regulations available.
There are around six pages of information in the portion that applies to hydraulic hoses, which includes everything from labeling standards to pressure and temperature testing.
There is one important point to keep in mind -this will come up later when I explain why even the “best” hose assemblies cannot be DOT approved- and that is that each requirement in the Standard carries equal weight; therefore, if a hose fails to meet ANY requirement in the Standard, it will not be approved.
As an example, a hose that matched all of the performance specifications but was labeled in lowercase letters would fail to be certified in a hypothetical situation.
Some of the characteristics required by the Standard also give a certain level of “idiot-proofing,” albeit at the sacrifice of absolute maximum strength or safety. Because of Ferrari’s inability to innovate, the 5-point safety harnesses in US-spec F40s were replaced with those awful motorized-mouse single shoulder belts, which are still in use today.
However, there are a couple of tests and requirements that are particularly difficult for stainless-steel hoses to meet. The majority of the “performance” specifications in the Standard are easily met by all halfway-decent hydraulic brake hoses, but there are a couple of tests and requirements that are particularly difficult for stainless-steel hoses to meet.
These are the requirements:
One is the method by which the fittings must be connected to the hose. In accordance with FMVSS 106, each hydraulic brake hose assembly shall be equipped with PERMANENTLY ATTACHED brake hose end fittings, which are attached to the hose by deformation of the fitting about the hose by crimping or sagging which means that the fittings must be permanently attached to the hose by deformation of the fitting about the hose by crimping or swaging.
A dumb end-user will be unable to tamper with and weaken the fittings since they can’t be loosened because of the way they’ve been crimped in place.
I believe this is a positive development from the standpoint of product liability… Although this rule is non-conforming, it does not rule out the use of the absolute best fittings available, such as the nip and cutter Aeroquip Super Gem or the Earl’s Speed Seal, which are both DOT approved but not DOT-compliant.
The “whip-resistance” test is performed. Using this method, you will attach the hose on a flexing machine, pressurize it to 235 psi, and then spin it at 800 RPM for 35 hours.
Steel-armored hoses were subjected to this test and it was discovered that they were more often than not to bend right at the junction between the hose and the hose ends. Once in a while, the stainless-steel braid would begin to fray, and the broken wires would cut into the inner Teflon liner, causing the liner to rupture.
One brake-hose manufacturer attempted to have the whip test modified, stating that their stainless-steel hose could easily pass the test if only a supplemental support were provided during testing to relocate the flexing-point away from the hose-ends. The manufacturer was unsuccessful.
The National Highway Traffic Safety Administration made a decision on the matter in August 1996, opting to allow manufacturers to employ the extra assistance… However, only on the condition that the identical support was employed when the hoses were fitted on an actual car was the experiment successful.
The Federal Motor Vehicle Safety Standard 106 was revised to include the usage of the assistance, and the new standards became effective in October 1996.
Stainless-steel brake hoses that had been “DOT-approved” went on sale almost shortly after.
So now you know what it takes to get DOT approval. Continue reading for more information on why you might want (or might not want) stainless-steel brake hoses on your car… Continue reading
There are three reasons why stainless-steel brake lines should be installed:
- They have a racy appearance.
- Because they do not swell like rubber lines, they may have the effect of firming up your brake pedal.
In addition, if you do a lot of off-road driving, the stainless-steel braid may keep your lines from being perforated by rocks or other debris.
The problem is that because stainless-steel lines do not bulge with age and because the inner Teflon lining is concealed beneath the braid, there is no straightforward way to evaluate the lines for indicators of impending failure before they fail.
The fact that the lines are replaced at least once a season isn’t a major concern in the context of a race car. It can be a problem on a street transport, as the majority of passengers are likely to allow YEARS to pass without even looking at their lines.
As a result, many individuals advise against using stainless steel lines and instead opting for rubber… Their anecdotal proof of steel lines exploding catastrophically and without warning will be more than willing to provide you with that evidence.
I haven’t come across any examples of this type of failure that specified whether the lines were as follows:
Attached correctly to the proper hose ends, and properly fitted on the vehicle.
In any case, Speed-Seal hose ends function in the same way as Swivel-Seal ends; the hose end can be swiveled once it has been assembled. The nipple/cutter system on these ends was specifically designed to prevent the hose end from being blown off the end of the pipe… It has been a long time since I have heard from anyone who has firsthand experience with one of these hose assemblies coming apart, and until I hear back from someone, I continue to use “genuine” stainless-steel lines on my car and change them on a regular basis.
THE FOLLOWING IS IMPORTANT: The lines that your performance-parts distributor will sell you are made using no-name hose from who knows where, and the hose-ends are simply swaged-on fittings that are a recipe for catastrophe if something goes wrong. Neither I nor anyone else will place these on their vehicles, and I strongly advise against doing so as well.
There are now stainless-steel lines that have been “DOT-approved.” I have no idea what these are, but I have a sneaking suspicion that they are still using low-quality crimped-on hose ends. I’m not going to put them on my car till my doubts are dispelled as well, unfortunately.
If you do decide to install stainless-steel lines in your vehicle, you should be aware of the following points:
You must ensure that they will not kink, twist, or stretch under any combination of wheel droop, bump, or steering when you install them. Because the stainless-steel outer braid will cut through anything against which it comes into contact, you must ensure that the lines do not rub back and forth over anything of importance during installation.
The failure of stainless-steel lines has been reported to occur when dirt becomes trapped between the outer braid and the Teflon lining… Dirt is abrasive to Teflon, which can cause it to burst as the braid swings back and forth in space. Looking at the stainless-steel lines on motorcycles, you’ll notice that many of them are enclosed in plastic tubing, which appears to be an attempt to eliminate this problem. The tubing also has a significant impact on the abrasion problem that was previously addressed.