Plainsman

First, I have no intention of cross chaining- but - I’m trying to finish a bike set up, and I used the big-big-don’t run through the rear derailleur chain sizing method. I was installing the chain with both derailleurs slack, so small-small. This is what I got. Should the rear derailleur be practically horizontal like this?

dsbrantjr

Your derailleur is at/near the limit of the amount of chain it can take up but it is still tensioning the chain so you should be OK. As you said you shouldn't run in small/small but you could. A slack chain won't break anything but a chain too short for big/big (and you should check this, gently) will.

Iride01 

Did you look at the Shimano DM (Dealers Manual) for your sizing? It's slightly different depending on how many chainwheels you have and sometimes whether is ss or gs.

oldbobcat

Maybe. While it appears a little on the long side, it would be helpful to see what it looks like on big/big before trying to shorten it. But many experienced riders don't use small/small anyway, because of chain slap or the chain rubbing on the inside of the big ring. And a little too loose is preferable than trying to go a little too tight.

Plainsman

I did. I’m running a 50/34 front with a 12-30 ten speed cassette. Anything over a 28 tooth suggested the big-big method without routing through the derailleur.

Iride01 

Hmmm. Pin or quick link? Though that looks like more than that would account for. I too would be interested in seeing how stretched out the cage is with the big/big combo. However I'm only used to gs and other long cage dr's. Yours is a short cage isn't it?

woodcraft

I'd be surprised if that was really big/big + 1 link sizing.

It should look something like this:

Iride01 

You may have exceeded the wrap capacity of the DR. 50-34+30-12=34. What model ultegra is that? 6600 with a short cage is 29 or less.

You might be able to cheat and shorten the chain more, but watch your b-screw adjust and make certain you aren't going to suck up the DR one day while riding.

Miele Man

Small/small is no too bad but accidentally going into the big/big can be catastrophic. I had a bicycle where the shop installed a new chain that was a bit too short. I came down a hill, shifted and then went to sprint across a two lane high only to have the bike lock up and I fell. Turned out the shift I had just made was into the big/big combination. Fortunately the 18-wheels coming down the highway was far enough away that i was able to get up and grab my bike and make to the side of the road.

Cheers

Racing Dan

If this is small-small you are fine, unless the top jockey is rubbing on the chain. It appears not to. Imo better to have it slightly long than slightly short, because mechanical shifting does not prevent big-big.

tomtomtom123

If Big-big already has your cage fully extended +1 or +2 links, then there is nothing you can do. You don't need the small small anyway, do you? My outer most 3 cogs on small-small have too much chain slack so the pulleys rub, but I purposefully exceeded chain wrap capacity because I wanted a wider gear range and can't use a longer cage because I have a 20 inch wheel. I don't mind because I won't use those 3 gear combinations.

noglider 

Too short is dangerous, but too long generally isn't, so err on the side of too long. And cross chaining is bad but it's not like you're going to die or anything. I do it sometimes for a bit because shifting to correct it is not worth the trouble.

grizzly59

If the bike is upright with wheels on the ground as if you were riding it and you aren't rubbing chain at the RD, you should be good as to small/small. Don't ever cut the chain too short big/big. As to the whole drive system working ok, you may be able to go over the RD tooth capacity a little. The RD will list a max cog size for the rear. If the shifting is crappy, the RD may not be able to handle the big cogs even if the chain length is ok. It's in the geometry/design of the RD.