Trying to install mudguards - what's with this hole?

craker

A picture paints 1000 of them words-



I thought I could put a bolt through it to attach the mudguard to but it's not drilled through. It's not tapped so I can't put a bolt into it. It looks like there's a boss on it so it must be there for some reason, or is it just to let out hot air during welding or drainage from the frame?

Either way what do I bolt my mudguard to... ?

The bike is a 2005 aluminium Fort supposedly Audax ready.

monkeycowboy

That almost looks like a grub screw? Can you undo it with an allen key?

getprg

That almost looks like a grub screw? Can you undo it with an allen key?

+1 - although looks like you would need to apply plenty of WD40 to ease it off before having a go at unscrewing.

However IME when fitting SKS guards for example it is not essential to fix leading end of rear mudguard to chainstays bridge by bolting through it. The SKS fixing kit usually includes a spring clamp that will clip round the bridge without bolting.

MichaelW

Looks like some kind of rivet. You can get threaded rivets for inserting into aluminium frames.
I usually drill the mudguard 1cm from the tip and use a small ziptie around the bridge, it holds well and lasts for years. much better than the metal bracket.
With narrower frames, I also nibble away at the sides of the mudguard to form two recesses which grip and hold the mudguard in place between the stays. If you remove too much, it won't grip.

desweller

Mine is drilled through. Are you sure it's not just full of crud.

gosport_commuter

Looks like a rivnut to me, should have a thread in it, but maybe its knackered. try m5 and m6 bolts, failing that maybe you could drill it through and use a bolt + nut.