jb wrote:One observation on modern hydraulic disk brakes on bicycles: if you don't mess with them they don't normally give any trouble for the lifetime of the product. Its only when people attempt to change the fluid that problems begin.
As I see it there is so little fluid in there to begin with that they have to be set up at the factory under very clean conditions with all air removed from the fluid that your normal garage DIY enthusiast cant hope to replicate. changing the pads is all one should ever do.
except that any system will -sooner or later- become contaminated with water, this is inevitable. If it is a system running DOT fluid and you don't change it regularly, the system will fail by internal corrosion, and may well boil up in service before then. Water gets past the seals into mineral oil systems too, although I think it doesn't happen as quickly.
Bleeding hydraulic systems is not that difficult to do, it just takes a methodical approach and a reasonable level of skill. But it isn't really on by the roadside, and it isn't cost-effective on a £50 brake at current workshop labour rates, either.
The outcome of this is that your typical inexpensive hydraulic brake is effectively bin-fodder as soon as it starts to misbehave, or when it is a few years old and needs the fluid changed, unless you can fix/maintain it yourself.
Cable operated brakes are a lot more practical to deal with when they need work (which might be more often), and generally don't fail without any warning at all; things like frayed cables and loose bolts are things that ought to be found during routine inspections. By contrast a small percentage of (even quite new) hydraulic brakes will fail to a leak with no warning; factories that assemble these things are not quite as clean and as efficient as you might like them to be.
FWIW I use hydraulic discs on an MTB (and I really like the way they modulate most of the time) but I wouldn't have them on a road bike.