Seriously. I always err on the side of caution having had one set down to the metal and wreck a rotor, and hence I always carry spares with me on a ride. However, I've heard said that you can run them right down until the holes on the backing (pad wear indicators, allegedly?) wear through. Is this right? Because if you did that I'd have thought the spring that keeps them apart would foul and knacker the rotor, wouldn't it?

Second question – what does that spring do, apart from keep the pads apart to make it easier to replace a wheel. Apart from hassle, what's against running without the spring to try to squeeze a few more miles out of the pads?

I run mine until it rubs the spring clip.

The spring stops the pads from rattling.

The spring won't knacker the rotor, it'll wear away really quick. Either keep an eye on them during post ride cleaning and change when low or wait till they stop working and replace.

…this really is all smoke and mirrors, isn't it? 😉

Don't reccomend leaving them to the last bit of material. Was doing the bottom bit of a big long descent – hit the brakes and the final bit of pad material gone torn off the backing plate leaving me with no effective front brake. I was taking it relatively easy so had not left braking to the last moment, but if I had it would have been high speed down a boulder slope

I wore a set of pads on my old Julies down to the backing (on one side) and was quite impressed what little effect it had on braking ability & damage to rotor.

Now, my brakes have got those spring retainers & you can generally here that twanging the rotor – it's then time to change.
I have had a spring get caught in the rotor & ripped out, but it didn't do any (visible) damage.

My pads bounced out in the Alps and I could still brake using the pistons.
Quite scarey though.

Ditto not leaving to the last sliver of pad

I had the old superstar pad / backing interface failure (so only the bare metal was left) at CYB and spent the rest of that ride in the wet with only front braking available. Made for some interesting descents!

ting ting ting ting ting ting ting ting ting ting ting ting ting ting ting ting ting ting ting ting ting ting ting ting ting ting ting ting ting ting ting ting ting ting ting ting ting ting ting ting ting ting ting ting ting ting ting ting ting ting ting ting ting ting….

that's how i know anyway

How do you know when to change your pads? You've just been for a ride in the Peaks…… it's time for some new pads.

when the squeal is so bad I would rather crash than brake

Yep, listen for the Hope Pro II freewheel style sound even when you're pedalling – that'll be the pad spring. (They work for quite a bit after that – you might be surprised*)

*one way or another.

Slighty before this point, disk was shagged too (not mine I was following smelling the burning metal and shreek sound from Cut Gate to Derwent)

There's a month or two left in that – sponsored riders might change them but the rest of us…