I shipped my bike across the country and managed to lose 1/2 of my KMC 12 speed chain missing link (quick link). I found a new sram 11sp quick link and reluctantly used that - it snapped on fine. I was wondering if there is a safety concern with this. I have not tried riding it - it's a tandem and wanted to check with the forum to see if this would work. Thanks in advance.

Safety? it should stay together...

Possible problem? the 11 sp. link is a tiny bit wider (around .2mm to .3mm, .010" to .012"),externally, so you might get a false shift or a click as it goes around the cassette. Internal width should be the same.

I can only say that I have had a quick link come apart on a bike only when I mistakenly used a 9 speed pin on an 8 speed chain. It, also, seemed to have set properly. Fortunately I was 1 block from home and at slow speed when it popped. I realize what I had done when I got home. The risk of it coming off, IMO, is too great to take the chance, A chain coming off can do some serious damage.

amazon sells them or most shops sell them easy to find.

No bike shop nearby (1+ hour drive) and Amazon will be 5-7 days out in delivery. ☹️

All you have to do is think about what would happen it you were standing to climb a hill or pressing down on one pedal while trying to get clipped in and the chain comes apart. If you're good with that, it's good to go. For the record, IMO if something causes you ask others "Is this a good idea?", the answer is usually "no". If you're going to be a cyclist, keep consumble spares on hand, that way you don't have to ride potentially dangerous equipment.

If the link engaged positively with no movement when the chain is not under tension, I might be inclined to ride it in an emergency on a single bike. Not on a tandem. Injuring a trusting stoker through my own negligence isn't something I'd want to live with. I'd drive to the bike shop or join Amazon Prime.

Hmmm. Well, I guess I won't be a cyclist. Thanks for the sage advice.

That's the plan. Thanks.

If you listen to the posters on this thread catastrophic failure is just around the corner on every ride. But if you think about it logically the 11spd link is new and chance of failure is not any greater if on 11 or 12 spd. As someone else posted there may be a chance of chain rubbing adjacent cassette or not shifting property.

Since the 12 speed chain is more narrow, the 11 speed link will not fit as tightly. More potential, however small, for loosening. That said, OP has considered the additional responsibility that comes with the tandem and moved on.