The price of Shimano chainrings seems to have skyrocketed so I've been keeping an eye out on ebay. I have an XT M752 Octalink chainset with a standard 4 arm, 104mm BCD (outer ring) setup. I picked up a 44tooth Deore M510 ring cheaply on the 'bay as a spare for when the XT one goes (I've already got Deore M510 steel granny and middle rings fitted).

It's just arrived and what I didn't realise is that it's a version that's been drilled to take a chainguard and as such doesn't have a chain drop pin (the pin that usually protrudes from the outer ring behind the crank to catch a dropped chain).

So, do I actually need a chain drop pin for safety's sake or can I get away without one. I'm assuming that it's hardly critical and I don't recall ever having lost a chain over the outer ring anyway, I only ever seem to drop chains over the granny ring (and then only rarely). I'm not sure what the benefit of catching a chain on the pin rather than letting it drop onto the axle (which is where it usually ends up if it drops over the granny ring) but I suppose if you're shifting up to the outer ring you're liable to be going faster than you would losing it off the granny, so maybe it is there for a reason. I don't want to put a chainguard on!

I suppose that the other question is where 4 or 5 drillings through the ring will weaken it at all, I don't really mind them being there for the price I paid as long as the ring's sound.

I don't think it would drop harmlessly onto the axle, it would get wedged between the soft alloy crank arm and rings. But then its the same situation with the rear cassette, we all take those crappy plastic spoke protectors off which are meant to protect the spokes from being gouged by the chain when it drops off the top of the cassette.

As long as you keep your gears set up well, I can't see a problem not having the pin.

I guess if you lose the chain into the crank it will wedge into the gap, you carry on pedalling and as it is wedged you will tear off your front mech and rear mech in quick succession, maybe, but I might be guessing, a lot.
Could you somehow fasten something into the space to replace the pin and reduce any fears based on totally unsubstantiated internet scaremongering?

Could you not just drill a little hole and put a nut and bolt through it you are concerned? Countersunk one would look best.

I've had them fall off the outside a few times, but I can't imagine it would be dangerous or problematic.

I had thought of putting a bolt through. I haven't lined the ring up with the crank arm, but it might be that one of the drillings for the chainguide would line up. However, even a countersunk heard with stand a little proud, would that interfere with the shifting ramps/pins, I don't want to end up causing more problems than I solve?

I could always keep it as a spare for my hack bike and look at getting a chainguard for that I suppose.

Stick a chunky rivit through the bolt hole, but stop before the tool snaps the leg off. Then chop it to length with pliers/hacksaw.