I'm trying t fit a set of the narrowest chromolastics to my touring bike, but even so the guard is narrower than the chain stay bridge (which is a long way from the rear wheel). There's plenty of space around the wheel, and TBH it'd look daft if I trimmed it down to bolt up to the bridge.

Anyone figured out a way of bolting it to the bridge, or should I resort to mechano?

Ms Spanner bought some for her road bike last year.
I, being the supposedly mechanically competent one, was given the job of fitting (I think the words used were 'Why have a dog and bark yourself?).

Three hours, lots of swearing and two small puncture wounds later I put the lot in the back of the car and drove round to the LBS.

Shaun at Cooksons smiled the smile of a man who has access to REAL mechanics and told that one of his customers had broken two sets before admitting defeat and returning for the third to be fitted professionally.

Work of the Devil. I'd rather have a muddy bum than go through all that again. 🙂

Zip ties to the down tube above the front mech ?, thats what I had to do, plus side is that it makes the guard longer at the back so less filth thrown onto your back, down side is the front mech gets it all

Little confused by the OP, but I made spacers out of large Rawl Plugs and drilled/slotted the guards for bolts. Put a nice large washer between the bolt head and plastic to prevent it pulling through.

Would you like some picures?

as above, made a spacer from a felt tip pen tube, long bolt, nice and tidy. if thats your problem! post a pic of offending area?

I did as Steve Makin suggests, one zip tie through the mudguard then another round the seat tube and through the other zip tie.

plastic wine cork cut down to size with bolt through it to space the mudguard away from the chainstay bridge.
iirc it was one of Sam Singular's builds I saw that on: looks really neat.

I've used the cork trick too, works a treat.