How do you tell when a disc's worn out?

Giraffoto

Having only had the bike a couple of months I'm getting way ahead of myself here, but how can I tell when a brake disc is so worn that it needs to be replaced? There don't appear to be any gauge holes/grooves on mine (Avid clean sweep G2), and although all the braking I've done so far has only made them shinier, I'm quite keen to know when they're to be considered unsafe.

nicklouse

when to thin. which will be years away.

Chunkers1980

If you ride in grit and sand a lot then excessive/non-uniform (compared to new) pad wear is also an indicator, but pads cost from £5 a set to say the £30 for a new rotor, so you've got to weigh it up.

cooldad

You'll probably get rid of the bike before it happens.

Giraffoto

So the consensus appears to be: unless I damage them they're good for years. One less thing to worry about . . .

benpinnick

Yeah, if you wear out a disc, good on you. Ive never done it and some of my old hopes are 10years + old.

agg25

Yeah you might bend one, thats about the only time you need to replace them. Pads on the other hand....

ilovedirt

I know a friend who's worn some cheapo rotors down before, however decent rotors won't wear down (or at least not without years of consistant use). I used my avid G2 rotors for years and they were still fine.

stubs

Check it with a micrometer lots of discs have the minimum thickness engraved on them.

I must be well hardcore because my Avid G3 front disc is nearly ready for the salvage bin after 7 months and the back isnt much better. The G3 discs are made out of cheese and not very tough cheese either mini Babybels I reckon .