Can anyone tell me what this thing is – and how I’m meant to use it. 3 of them came with a new Shimano rotor.

it goes onto the mounting bolts – 3 of them – 6 bolts – do the maths…
Those really nice drawings that Shimano put in their instructions you read FIRST are really helpful…..

But for why? Never seen ’em before. Is it a washer?

It’s a badger deflanger. Metric one, obviously.

Did your rotor come with bolts?

Did they have heads that are square or triangular?

If it’s like mine, then yours is upside down. If you turn it around it says TOP. That’s as far as I got. They are spaced to fit on the bolts as hammyuk says, but I couldn’t work out why they are there so left them out. I will die, but hopefully not from this.

Some kind of locking tab washer?

They are to stop the bolts loosening during use. On the older version you just bent the soft metal edge up to mate with the flat face of the bolt. Its all about lawyers and liability …

http://bike.shimano.com/media/techdocs/content/cycle/SI/DiskBrakeSystem/SI_8KL0A/SI-8KL0A-001-00-Eng_v1_m56577569830750014.pdf

They are fairly pointless. I don’t bother with them.

sbob, that’s actually the older version which you had to bend up. The newer ones in the pic don’t need to be bent with a screwdriver, but work like a spring washer instead.

Cheers all. I’m going to fit them and therefore avoid death.

They are the locking washers, as in the instructions.

Little fact for you – those pictures they put in the instructions and on certain things are called “Idiograms – sometimes I wonder if they’ve missed a letter out….

no idea, but you have a strong life line and are destined to have many plump children

Exactly how much patronising can one man do on one thread?

Microteet spanner.

Bone for a tiny steel dog

Looks like you should have gone to Specsavers.

Is it not a mask for a really tiny superhero?

In defence of the OP….
I just fitted some shimano rotors that came with the same locking washers and the instructions supplied were for the older type with fold up tabs so not that much use 😉

Hammyuk ya big galoot – the rotor came with a whopping 12 sheets of A3 instructions covering a multitude of languages – but none carry your aforementioned idio(t)grams of the tiny metal dog bones / mini superhero masks / micro teet spanners / locking washers.

Is that OK with you, or not?

Touchy…

Important rule of spannering is to always have bits left over at the end, no?

Gonad cuffs