From a guy that I trust. Your results may vary but is your life (and your passenger's life) worth a measly $100.00 "savings" ?
I'm sticking with OEM line specs - forever.
I have them made locally from Parker or - my favorite - Gates (made in America) for 1/2 the price of Spieglers - they are NOT rocket science. Grainger made my last set in a day.
10. Longevity of BMW Motorcycle brake hoses; specific problems......and a full discussion about SS braided-covered hoses:
Although this particular problem used to be very rare, it is not all that rare nowadays. The BMW stock hoses are VERY good and LAST for quite a few DECADES; if you do not hang them by the calipers nor do anything like using a clamp/pinch device on them (both of which some old-time mechanics did for convenience or to stop fluid leakage during some types of service. NEVER EVER do those things! BOTH of these BAD practices CAN excessively bend the hoses INTERNALLY, especially bad at the fittings ends if hanging the caliper...the damage is almost always HIDDEN. The small diameter internal stiff plastic tube (the thick rubber hose, whether SS braided covered OR NOT, covers that internal tube) kinks, and may produce a partial-one-way flap. Bad hoses from normal use are fairly rare, but MIGHT happen eventually, but I have seen MANY...probably MOST... that went 1/4 million miles and are several decades old, that were still fine. SOME stainless steel hoses are particularly susceptible, having extra thin and/or extra small diameter internal tubing, and the fluid returns slowly anyway, or the kinking is 'easier' to become a problem.
There is a LOT of pressure from the master cylinder, into the hose and caliper(s) when using hand or foot pressure. That pressure needs to relieve itself when the lever is released...by a quite small amount of fluid coming back to the master cylinder, and it should do so at a fairly fast rate. In some instances of NO damage, or with damage in MANY instances, the fluid returns too slowly (hopefully it DOES return)...this can give you problems with quick multiple brakings. AFTER the major part of that pressure is relieved, one hopes, by releasing the lever, the final bit of pressure relief effect is from the caliper piston O-ring deformation, now pushing the piston back a quite small amount. There is NO SPRING pushing the piston back into the caliper EXCEPT that very small spring effect of the O-ring, usually a square-sectioned one, that surrounds the caliper piston.
If a flap or kink develops in the inner tube of the hose, or the caliper is corroded, or the tiny return hole of the master cylinder is clogged, or partially clogged, the pressure maybe only partially relieved, at best. Even a partial non-release will cause problems, the least of which is, after awhile, a change in surface of the pads, and MAYBE some squealing and USUALLY poor pad friction. To make this clear, the pressure might be released very slowly, or not at all, or incompletely. The worst situation would probably be enough heat from enough pad friction when you are not even doing any braking...... to allow brake fluid boiling (especially if the fluid is old!), causing bubbles,leading to NO BRAKES after you are riding awhile !!! The brakes could also freeze-up....and suddenly. One way THAT happens is that excessive contact pressure from pad to disc causes excessive heat in the caliper, and eventually the fluid expands/boils, and you can get very sudden full-on braking.....actually, so hard that the front wheel SEIZES. Over the handlebars YOU GO!...or, you slide-out.
Stainless Steel braided lines are NOT generally any better overall and potentially FAR WORSE, and I recommend you do not willy-nilly replace stock hoses with them. There are exceptions, but that is a good general rule. I will discuss exceptions later in this section.
Many aftermarket Stainless Steel braided hoses have lousy internal construction, and some are so bad that the fluid return is not fast enough during multiple short-time braking efforts due to the inner tubing having too-small a diameter. Another problem with some aftermarket SS hoses is that they won't pass the industry standard WHIPPING test...a test of constant flexing to simulate long term use; and, the 304 SS material will work-harden, then can break; also the bad braiding area can rupture...and you get a bubble situation that can blow out. SS hoses are NOT just SS braid covered "standard" rubber hydraulic line hoses. SOME premium hoses WILL pass whipping tests. ASK! for SPECIFICS.
If you use SS hoses be SURE that the OUTSIDES are covered by plastic tubing ...not just to protect painted surfaces, but to HELP avoid the common SS hoses/lines failure modes.
I know that this is probably controversial; but, except for racy appearance, I do NOT like SS braided hoses. I think the STOCK hoses are BETTER, in nearly every way (exception: Racy looks), if the braking system is stock, or close to it. There are some situations, such as adding very long brake hoses for such as a sidecar, that ARE helped, in braking performance, with SS covered lines.
Re-stating earlier information: If the inner diameter of the inner plastic tubing is too small, then relatively rapid multiple-uses of the brake lever can build up relatively UNrelieved pressure in the tube.... the brakes do NOT have TIME to fully release. That means heating-up of pads, calipers, discs. The smaller and/or thinner the inner tube, the easier it is to get KINKED. When a kink occurs, it closes-down the size of the tube. For RETURNING fluid (to the master cylinder), that is BAD, as the returning fluid is under VERY LITTLE PRESSURE after the lever is released, and the caliper pistons may not return to proper position!
Additionally: When you pull on the lever, the pressure in the tubing is monstrously increased, which can easily force OPEN the 'kink', and allow the caliper pistons to move outward. Upon lever release the pistons do NOT RETRACT FULLY, IF AT ALL. This leads to high wear of the pads, overheated and warped discs, excessive deterioration of the fluid, and potentially BAD things to YOU.
BMW hoses are not overly long, which tends to minimize the potentially SLIGHTLY softer feeling (from using non-metal-braided hoses). Properly bled brakes have a FEEL of the lever such that the brake lever is NOT super-abruptly-super-hard. You would NOT like it that way, as you would find it MORE difficult to properly engage the exact amount of braking you want. BMW has a tendency to use larger Master Cylinder sizes, which makes things a bit abrupt in a properly bled system. This is why smaller master cylinders are popular (and safe, if one does not go too far), besides the braking help.
MUCH of the "my brakes are better with the SS hoses" is a bunch of nonsense, and you are being fooled.
Installing new hoses of any type MAY lead to a lot of cussing and a LOT OF LABOR....as you try to eliminate bubbles of air.
NOTE: as described earlier in this article, ALL our hoses, stock and aftermarket and SS too, age over the years, although VERY SLOWLY if not abused. Still, there may be a tendency, however small, but perhaps now increasing....for a hose to have an internal flap problem in which the hose allows pressure to go to the caliper, but does not allow (or only slowly) pressure to be relieved fully at lever release. This will result in insufficient caliper piston release. You can check for this by hand rotating the wheel and checking for anything more than lightest friction from the caliper pads. Of course, the problem could also be the piston and O-ring, MC return hole, corrosion, etc....as described earlier.
One of the PRIME reasons folks put on SS lines is because they look racy..........or....they think it will fix softness in the lever....which it will if the softness...sponginess...is due to bad bleeding....or truly bad hoses (like a blister). If they now bleed properly, and thoroughly, compared to what wasn't done previously, installing SS covered lines can greatly improve braking feel (if reduction of sponginess means anything). That it does not improve actual braking power. A stock rubber hose versus a SS covered hose can, even with both being brand-new, and proper bleeding on both, show just a barely slightly harder lever with the SS. That is because the SS covering tends to reduce the flexing of the rubber hose..........and sometimes this is ALSO due to the smaller internal tubing of the SS line. This does NOT improve actual stopping power for the same amount of lever hand pressure. One last word about SS braided lines/hoses: Many independent repair centers, many dealerships, etc., all do not know all these things about the hoses. Many have a $$$ interest in selling you SS covered hoses. Many who DO know these things also know that you are not likely to wear out the hoses, or have problems. While I think they slough-off these things for sake of profit, I also think that many THINK that because some bikes came with SS covered hoses, that ANY bike is helped. I also have other thoughts, perhaps better not mentioned here. Please re-read, carefully, this longish section 10. Your bike is YOUR bike, and what is done by you, and others, to YOUR BIKE, is YOUR ultimate responsibility, when you accept modifications.
Frankly, I do NOT like SUDDENLY VERY hard brake lever action...I find that situation results in difficulty in modulating braking power, particularly when using brakes in turns, or desiring to power the brakes just under where the tire might slide. SS covered hoses can have their own problems as I've noted, with failure to pass whipping tests, being more susceptible to damage from the BAD practice of hanging calipers by the hoses; and, of course, the problem I mentioned of having too small a diameter of internal tubing, and that can lead to failure of the brakes to respond in the release mode fast enough, in multiple braking situations too. I have run into a quality problem myself, ONCE, and had to send the SS hoses back to the maker for better quality ones (sidecar rig, LONG LONG front hoses, due to the type of front end).
Most people never have a problem with SS lines for long periods of time. However...most stock hydraulic rubber hoses (these have internal tubes too, usually larger diameter) last 20 years or even decades longer!! Note that SS covered brake lines are really very similar to 'rubber brake hoses', but the type of rubber, number of layers (if multiple),
woven threads area between layers (if any), size and quality of the internal 'plastic' tubing at the center, and method and quality of fastening the hose and SS braiding to the end fittings, can vary considerably with manufacturer and model.
For quite modern bikes, where every little wee thing for improved braking is taken into account, and SS lines are standard, reverting to rubber, that is, no SS, will definitely show up any slight flexing. Thus, it is my opinion that if you have a bike that CAME from the FACTORY with SS covered lines, you should continue, otherwise, you are on your own with installing SS braded hoses onto a bike, such as an Airhead, that did NOT come with them.