I am gobsmacked!

[Levo-Lon]

The reach isnt adjusted. There is a little circular thing with numbers 1-5. Rotating this adjusts the bite point of the brake. There is an identical device on the clutch lever, altho I never tried that one.

no thats nothing to do with pad adjustment..
its the span only..so your moving the lever further away so in effetc you commpress the piston sooner in relation to your hand grip span ,so your less likely to pull the lever to the bar..the master cylinder piston is not adjustable..
if you were to push it even a few mm you would have a fluid lock as soon as the fluid warms..and the wheel brake will lock on solid until it cools..

 

[Salty seadog]

Hydraulic discs adjust themselves as the pads wear. Car brakes do the same.

Can someone explain how, genuinly interested?

 

[I like Skol]

Can someone explain how, genuinly interested?

Yes, really simple. As the master cylinder returns to the rest position it passes a small port that allows fluid from the reservoir to flow in. This also allows expanded fluid and fluid pushed back up the line when fitting new pads to flow into the reservoir. As the pads wear the calliper pushes out further and retains additional fluid, this is replaced from the reservoir each time the brakes are fully released. If you think about it like pushrod brakes then the extra fluid getting in to the brake line is like making the pushrod longer to compensate for wear.

 

[Levo-Lon]

Too add to the perfect description above..
hydraulic brakes have 2 rubber sealing rings in the caliper that seal the piston and caliper to stop fluid leaking out...these are what make the brakes relax after application so the brakes dont drag.
the flex ' elasticity'in the seals retracts the pads by a very small amount..
dirt and old seals ' loss of elasticity' can often cause the brakes to bind or cause excessive lever travel depending on whether the seals are stuck with dirt..tho dirt and corosion are the big problem as a rule over time.
a good clean of the pistons is essential when fitting new pads as just shoving them bach un-cleaned is the start of future brake problems..if you cant buy new seals its often the death nell for the brakes.

so when you fit new pads or ever need to retract the caliper pistons take a few mins to clean them first with a small tooth brush or something that will get into the nooks and crannies , brake cleaner works well for washing down removing dust..

 

[Cubist]

XT brakes have bite point and lever reach adjustment. The servo wave shape of the lever cam means that the pads sit out of the way of the rotors rather than nearer to them. I have XT brakes on all my MTBs and wouldn't use anything g else. They really are fit, adjust for lever feel preference, and forget.

 

[Drago]

I don't know of any hydraulic brakes, be it bicycle, car or even aircraft, that have such and adjuster. It'd be an utterly pointless mechanism on a system that very effectively self adjusts with use and wear.

There are some with an adjuster, such as the super XT stoppers, but that affects the valving and the feel rather than any physical measurement at the pad-disc interface, and then there's lever span adjustment. But a pad adjuster....? About as useful as a periscope on a parrot.

 

[Levo-Lon]

Periscope on a parrot!! Quality @Drago

 

[Profpointy]

Periscope on a parrot!! Quality @Drago

yebbutt what if a parrot needs to peep over the gunwails on his pirate ship when it's under fire?

 

[Levo-Lon]

yebbutt what if a parrot needs to peep over the gunwails on his pirate ship when it's under fire?

as in 'I see no ships?"