Chain drop prevention pin

[Endo]

Hi,

I'm hoping the forum might be able to provide some opinions on a chainset replacement which I'm carrying out.

I'm replacing my current RPM chainset with 165mm cranks for a Stronglight XD-2 with 175mm cranks which should be much more suitable for me. I'm re-using the chainrings as these and the rear cassette are the same age with plenty of life left.

The XD-2 has one of the five mounting arms recessed behind the crank arm and this means the large chainring has to be rotated so that the chain drop prevention pin is no longer directly behind the crank arm but slightly offset of the arm.

The pin is fixed in the ring and cannot be removed.

I have never had a chain come off in between the main ring and crank arm but, no doubt, it could happen. I believe a correctly adjusted front derailleur should prevent this from happening. I could also buy a brand new chain ring with a prevention pin in the correct place.

What does the forum think? Keep the FD adjusted or buy a new main ring?

Thanks a lot everyone in advance.

[CREPELLO]

Make a new pin> Drill a hole in the correct place and tap it out for a regular steel screw to go in.

[Si]

I'd carry on with what you've got. Not all chain sets have these - thus although a nice feature they are not crucial.

[Endo]

I like the engineering solution! If I had a workbench and a set of taps I would defininetly do it.

Thanks Si and Crepello.

Regards, Nigel

[thirdcrank]

Once upon a time - in the far off days when TA used to make some extended chainwheel fixing bolts to do the job (costing an arm and a leg then, just as they do now) a slice of cork used to be wedged in by some as a cheaper alternative.

[531colin]

Love the piece of cork!
No need to drill and tap, just drill and use a nut and bolt. Not quite so elegant, but its behind the bloody crank, after all!

[stoobs]

I suppose that on some set-ups, you could end up with the chain jamming, but if it doesn't jam, I wouldn't bother, especially if you've never had it drop off there anyway.

I thought that in many cases, the pin allows you to pick the chain up again by rotating the cranks, maybe without even stopping. All it means is that in the event of the chain dropping off, you'll probably have to hook it back on by hand.

[Chuck Glider]

Thanks for asking this question endo. I've been wanting to ask exactly the same one.

Before you drill, have you tested the chainset as is, meaning with the pin slightly ahead of or slightly behind the crank? What happens if the chain falls off? It may be that it's fine as is.

[ddddddd]

I like the engineering solution! If I had a workbench and a set of taps I would defininetly do it.

It's easier than that. With a basic Al chainring you don't need a tap. Just use your screw.

Simply drill a hole of the right size, it doesn't even have to be precisely perpendicular.

Don't bend the chainring. Probably best to hold it flat on top of a piece of wood scrap. (With concrete or something underneath, not your carpet.) Then after you have drilled the hole, push down hard as you start off the thread. - Do it defininetly[sic] - yeah.

[niggle]

I like the engineering solution! If I had a workbench and a set of taps I would defininetly do it.

It's easier than that. With a basic Al chainring you don't need a tap. Just use your screw.

Simply drill a hole of the right size, it doesn't even have to be precisely perpendicular.

Don't bend the chainring. Probably best to hold it flat on top of a piece of wood scrap. (With concrete or something underneath, not your carpet.) Then after you have drilled the hole, push down hard as you start off the thread. - Do it defininetly[sic] - yeah.

Best use a "self-tapping" screw for this method: its in the name