Hydraulic brakes numpty questions

[srw]

How often should I be expecting to bleed the things? What are the symptoms that indicates it's time for a bleed?

And for a longer term question - how long should the system last? Are there any signs that the whole thing is about to perish?

For reference, we've got a Formula Hope combination cable-hydraulic system on our Santana tandem. It's probably about 10 years old, and I don't want to spend too much time on maintenance if it's time for replacement. Santana are now selling new bikes with cable discs, which is the obvious alternative route and would make transport easier too. Equally I don't particularly want to lose hydraulic braking power with 30-something stone of tandem plus riders gathering speed down a twisty road and have to rely on the parking rim brake and the front brake without notice!

 

[lpretro1]

Depends a little on what type you have.But if the brake is working fine then it is best left alone as you can cause problems by bleeding it especially if you are not familiar with the process. If you have ones that use mineral oil then the oil has a much longer 'shelf-life' 4-5 yrs - DOT based oils have a shorter 'shelf-life'(2-3 yrs) and the fluid is much more prone to absorbing water (hygroscopic). You should only bleed a brake a) if there is air in the system. Symptom of this is the lever is spongy on first but if you pump the lever several times it seems to stiffen up; b) if you have to do a caliper rebuild or lever rebuild and you have opened the system up so air gets in. Don't ever use a bottle of DOT fluid that has been on the shelf any length of time after it has been opened - it will be no good. A sign of DOT fluid needing changing is if you take the cap off and lok at the reservoir - it should be a light colour - if it is dark looking it needs changing. For all fluids if there are bits of black stuff or sediment etc then also time for a change.
Always ensure you know what fluid your brake needs - you CANNOT mix mineral and DOT - you will kill the brake seals.