On a century ride, I saw some bikers on the side of the road standing around. I stopped to see if they needed help. One guy said both of his derailleurs broke at the same time. I obviously had to see this so I got of my bike to look.

Everything looked fine but the chain looked pretty tight. I said, lets try to shift it, the owner said can't because it is busted. I tried to turn the crank, nothing would move and that is when I saw the problem, his chain was on the big chainring, biggest sprocket and his chain was a couple links too short and was bound up really tight. I told one of the people to take the rear wheel off, shift the chain to a smaller sprocket, etc. They did that, got it back together, the rear derailleur appeared to work ok and was not bent.

I told him he was very lucky he did not damage anything. And I told him to stop at the bike shop that sold that to him on the way home to demand they add a link.

My point is, be very careful if you are riding with a combination where the chain is too short.

On my derailleur touring bike I can't use my smallest chainring and my smallest two sprockets on my cassette, the cage won't take up all the slack. But those gears are so cross chained I would never use them anyway. But I would rather have two unusable gears than have a chain that is a link too short.

I have never seen an Erickson Gizmo or even heard of them. Neat. Thanks for posting, you can learn something every day.

This is what I use on my rando bike. Brifter for rear derailleur, friction front.