When do you change brake block

[Worrying Will]

How do you know when it is time ot change you blocks. I have got a clue .

[Kevy427]

If you end up in a hedge

If the brake block has worn down below its holder (where the block slides in) then you'll know from the metal on metal screeching sound. If you've got a few millimetre's protruding then it may be time to invest in new ones

[Seasider71]

When the protruding bits of the block become flush with the rest of it - time to change.

[Jack Hughes]

Some have a wear level indicator.

Some have a pattern.

You can change when they hit the wear level indicator.
When all the pattern has gone
Or a fair bit before they hit the shoe! (you don't want to damage your rims as will as killing yourself).

[Jellybaby]

How would they wear down? Does that mean you use them?

[md6]

I would suggest on the weekend, or another time when you aren't riding...

[Worrying Will]

cheers all no need to panic just yet and yes JB i use them a lot.