Why's everything on fire?
Join Date: Mar 2011
Rep Power: 1
Some brake authorities state that 6-8 years is about the limit for "unlimited trust" service in the common rubber brake line as fitted to the 919, most cars, trucks, other bikes, etc., etc. Many (including not a few vehicle manufacturers) say 4 years.
The lines age from the inside out as well as outside in and as they age they candrop rubber particles into your brake fluid which can float to "interesting" places and gum up the works. They're also difficult to inspect - the outside appearance tells you nothing about the inside condition, and it's the inside that's most important.
The majority of quality SS line manufacturers (today - this didn't use to be true) say that barring abuse or mishandling, the line should last the life of the motorcycle. Replace it once, inspect it regularly (the semi-translucent nature and failure behavior of SS hoses that are DOT certified and properly made make inspection easy) and you'll be fine. Speigler's comment on it is this: "A generally unrecognized manufacturer’s recommendation is that all original rubber hydraulic hoses should be changed every four years to avoid failure. Spiegler brake lines are maintenance free and will provide reliable service for the life of your motorcycle." Other SS makers don't necessarily include the short lifespan comment, but they tell you the same thing about their products.
I replaced my 700's lines because I just didn't trust the originals at 25 years. That's a bit much to ask of any rubber. Took them off, cut them open, inside looked like crap and they should have been replaced for safety long ago. Lots of us have gotten lucky with old brake lines, but that doesn't mean we should press our luck. Brake lines will fail at the worst possible moment, we all know that. Better to jettison the old ones and fit new before it becomes a problem.
Better feel is another reason. No matter how good the rubber hose, by their very nature they expand a little whenever they conduct pressure. This means that some of the pressure you are applying is bleeding off into the hose expansion; it can also fractionally slow down the pressure front from the master to the calipers, but it is debatable whether this delay is humanly perceptable on most systems. The loss of feel due to the hoses expanding is not debatable, it is confirmed.
Bottom line: Safety, better feel, not expensive, problems have pretty much been ironed out (some OEM mainstream manufacturers are starting to include them as standard on sports and heavy duty models) - no good reason not to unless you are competing in concours events.
1986 Honda Nighthawk 700S
2002 Honda 919