robertv

So, I've got a surly crosscheck, totally stock with a double in the front and bar end shifters, the rear deraileur is tiagra. I've just started working as a courier and when I hop up a curb too quickly, or down a curb, or just throw the bike around a bit the chain drops off. This only happens when I'm in the little ring. It seems to me like this might mean the derailleur isn't tensioned enough, but I really don't know. It shifts through the gears fairly flawlessly. This is a pretty big issue as I do a lot of jumping up and down curbs over the work day, and I do get sick of putting the chain back on. I'm also worried that I might not notice it pop off as I rush into traffic and I'll get run over. Any advice? The guys I work with, even the ones with geared bikes, don't seem to know or care too much about mechanical issues. Most suggested just running a single up front, although I think the derailleur would still need to be tensioned properly. So any ideas? If I hold the bike in the air and shake it up and down hard the chain also pops up.

operator

1) Check that the chain is the proper (shortest) length
2) Check that the B-tension adjustment on the derailleur is optimal
3) Check that the limit screws for front and rear derailleurs are adjusted properly, in particular the low limit for the front derailleur is as close to the chain as possible with no rub while not affecting shifts (in the small ring/biggest cog combo).
4) Consider installing a chain catcher/keeper.
5) Consider learning to drop off curbs without a significant impact. This is riding style.

robertv

Ok, Your advice is good, but...
1) how do I do that? The chain is stock, I imagine surly put the optimal chain on it, if it isn't, how do I tell?
2) How do I do that and define optimal? really dumb the explanation down for me cause I'm ham-handed and tend to break little mechanical doodads.
3)rear derailleur seems adjusted properly as it shifts well and doesn't over shift. Front derailleur is on friction shift, but I don't think the limits are the issue, the chain comes off the bottom of the chainring, but I'll look at that anyway.
4)will do.
5) I do try to do this, in fact I do these things all softly enough that my u-lock doesn't fly out of my back pocket. Yet the chain does pop off. it even pops off if I hop off the bike then quickly lift the bike up and put it down against a wall. It's beginning to piss me off.

operator

1) https://www.parktool.com/repair/readhowto.asp?id=26
2) https://www.parktool.com/repair/readhowto.asp?id=64

Use the big/big method + 1 link. Don't assume anything about factory assemblies or shop final assembly quality.