Spurned on by another member, who challenged my way of thinking about asking questions, I decided to do a little research on the question asked. So here is a little information I found on the web about SS brake lines. Note: I did not write this, I just found it. Please feel free to add or correct where appropriate. I am still learning as well. Brake Line Facts and Fiction by Paul Wright So you want to buy some performance brake lines for your motorcycle, but can't decide which is best for you? We understand your delima. There are lots of different brands out there, including Russell, Goodridge, Fastline, Fren tubo, Galfer, and more, plus there are "-2" and "-3" sizes, and you have a choice of stainless steel brake lines, Kevlar brake lines, and even carbon fiber brake lines. How do you choose the right brake lines for your motrorcycle? I'm going to explain the facts about performance brake lines and explode some of the popular brake line "myths" we often hear, even from experienced racers that should know better. After reading this article, you will know more about motorcycle brake lines than the salesman at your local motorcycle shop, more than your buddies, more than just about anybody. In case you don't want to read the whole article, I will cut to the chase right here and tell you the brake lines you need to buy are made by Fastline, but if you want to know why, you will have to read further! HOW HYDRAULIC BRAKES WORK All modern motorcycle brake systems use hydraulics, and the physics behind this is pretty simple: liquids do not compress. Whatever pressure is generated in the master cylinder brake fluid is directly moved through the brake lines into the calipers, pushing the brake pads out against the rotor, creating friction and stopping the motorcycle. The design of a typical motorcycle front brake master cylinder and lever allows you to generate over 4,000 lbs of pressure within the brake system. That's a lot of pressure, but that's what is needed to stop a spinning brake rotor on a 400 lb motorcycle at speed. Since liquids don't compress, the pressure throughout the brake system is essentially equal at any time. The pressure in the master cylinder is the same pressure as in the caliper, and also in your brake lines. That is why you need good brake lines. They have to convey thousands of pounds of pressure from the master cylinder to the calipers. BRAKE LINE BREAK DOWN There are 4 basic parts to a performance motorcycle brake line. The fittings on the end, the teflon inner sleeve, the material around the sleeve that gives it strength, typically braided stainless steel, and usually there is a protective coating on the outside. We are going to take a look at each of these components and explain what works best. The fittings are either steel or aluminum, and we don't recommend any brake lines with aluminum fittings. Steel fittings are MUCH stronger, are less prone to vibration and stress fatigue failure, they are almost impossible to kink or break in a crash, and they do not deform when you accidentally over tighten them during assembly. Yes, the steel fittings weigh 1 ounce more. You can live with that. The Teflon inner sleeve is what actually contains the brake fluid, but it does not have enough strength by itself to stand up to the pressures in your brake system. The material around the inner teflon sleeve is the key to making a performance motorcycle brake line. The material used must be flexible but strong, controlling expansion of the teflon sleeve when pressure is applied to the brake system. The outer coating is there to protect the brake line (and your motorcycle) from abrasion as the motorcycle moves around and the suspension compresses and extends, causing the brake lines to rub against parts of the motorcycle. Years ago, many brake line brands came without any protective covering, and we saw many brake lines get rubbed nearly to the point of failure. Some brands of brake lines still come with no protective covering, and we definitely do not recommend them. BRAKE LINE EXPANSION DYNAMICS When a brake line expands too much under pressure, two things happen that you do not want - loss of internal brake system pressure which means a loss of braking power, and loss of "feel" at the brake lever. Let me give you an easy example. If you had a small round balloon filled with brake fluid, and you squeezed it in your hand, the ballon would expand anywhere it could, and it would feel mushy, and maybe even burst. If you placed the same brake fluid filled balloon in a small bowl the size of the balloon, covered the top completely with the palm of you hand and pushed down to compress the ballon in the bowl, the balloon would feel as hard as if it was solid. Remember, liquids do not compress, and the balloon can not expand when encased all around by the bowl and your hand. In this example, the balloon is like the teflon sleeve, and it needs something around it to control the expansion when pressure is applied. CONTROLLING BRAKE LINE EXPANSION The real trick is controlling the expansion, not eliminating it. If you could totally eliminate brake line expansion using a steel tube from your master cylinder to the caliper, you would have brakes that were so sensitive and grabby that manufacturers would have to re-think brake pad compounds and master cylinder designs. You need a small amount of expansion (about 4%) for motorcycle brakes to have the proper "feel" that is critically important to racers. Too much expansion and you loose braking power and feel, too little expansion and your brakes will be too sensitive to have good control at the lever. The reality is that most brake lines, even aftermarket "performance" lines, simply have too much expansion. The stock rubber lines that come on most bikes are fiber reinforced, but do not do a wonderful job of controlling expansion, and when they get hot, the rubber become softer, allowing more expansion. -2 and -3 BRAKE LINES EXPLAINED I sometimes hear racers claim they like the -2 lines better because they have better feel and braking power. The truth is -2 lines do have a different feel to them , but they do not give you more braking power than -3 lines, and in fact -2 brake lines can cause a serious problem not found in -3 lines (more on that later). First let me explain that the -2 and -3 terminology simply refers to the inside diameter of the brake line teflon sleeve, -2 being 2mm, and -3 being 3mm. Now if liquids don't compress, and any pressure created in the master cylider is also present in the caliper, how can the diameter of the brake line make any difference in braking power? Good question! Assuming the two brake lines have the same expansion percentage, there is no difference in the pressure deliverered by a 2mm line over a 3mm line, but there is a difference in volume. Most motorcyle front master cylinders have bore diameters around 14mm. The 2mm line volume is less than half that of a 3mm line, restricting the flow from the master cylinder, making the lever feel "tighter", and giving a different "feel" at the lever. This is why some people like the 2mm brake lines better than 3mm brake lines. Braking power is not increased, but the perception of the braking power does change. So why are so few brake lines made in the 2mm size? Most manufacturers know what we also discovered years ago with our own race team bikes - the 2mm lines do not flow enough volume to allow a fast retraction of the pads from the rotors. This means that when you release the brake pressure, the extra restriction of a 2mm line keeps your pads rubbing against the rotors far longer than with 3mm brake lines. There is no "return spring" in your calipers. The pads retract only as the fluid flows back out of the caliper, through the brake lines, and back into the master cylinder. Slower pad retraction caused by 2mm brake lines can cause your brakes to stay much hotter, inducing pad glazing, pad backing plate warping, brake fade, premature fluid break down, and even warped rotors in extreme cases. We do not recommend any 2mm brake lines. THE ANSWER TO THE PROBLEM If 3mm brake lines have plenty of volume, but 2mm brake lines offer enhanced feel, why don't brake line manufacturers have something in between to give you the volume you need and better feel? The answer is price and profit. The common line sizes available are 2mm and 3mm, so that is what is cheapest and most easily obtained by brake line companies to manufacture their brake lines. We are aware of only one company (FastLine) that specifies and uses the more expensive 2.5mm brake line, and they have it made with the correct weave of braided stainless steel that also gives you the proper expansion rate. How they keep the cost reasonable is a mystery, but FastLines cost about the same or less than other major brands.