How to make your bike unattractive to thieves?

I think you are approaching it the wrong way round.

On the whole (in London at least) people steel bikes for two reasons; to sell for money, and to use themselves.

Those that sell for money I think are either people looking for a quick easy sell for any money (crackheads, kids, etc.) or more professional theives who will scope and target bikes and probably have a good distrobution network.

Either way people have to want to buy what is being sold. So think about how you can make a bike that people are not going to want to buy.

The short ans imo is making a fucked up looking bike with no cool factor and then locking really well - IMO Skully's bike is more an eg of what not to do... pretty colour, nice saddle, redtape matching the clip straps...the fact that everyone loves it just proves how easy it would be to sell.

So things like plastic mudgaurds, shit looking saddles, dirty bar tape instead of grips, shit looking wheels (maybe fake rust them).

As for ppl stealing bikes to use, just stay away from fast hybrids or full sus BSOs.

Sorry you've lost me hugo, you think I'm approaching it the wrong way around?

Because what you describe above is exactly what I'm talking about. If the frame of a bike is it's heart or what the bike is built around then you can hide a really nice bike by rattle canning the frame a really naff colour (naff as in unattractive to thieves, so not satin black or bright red for example) leave the paint runs on it, maybe scratch it up a bit if it isn't already, make sure to cover the Reynolds 853 stickers!

If the seat post is carbon maybe cover it with a layer of masking tape. Masking tape gets grubby and nasty looking in no time. Have wheels built up for it that are light and strong and actually very good but not desirable, for example Mavic Open Pros over Velocity Deep Vs.

You could have carbon forks on it but rattle can them the same as the frame. Obviously you still lock it well but given the choice between your bike and something not as good but prettier and locked in a similar way I'm thinking a thief would go for the bike that would be easier to sell on, the not as good but prettier bike. If indeed he was even aware how good your bike was underneath the naff paint.