rbrides

In the attached picture of my bike in the Big-Big gears, is the derailleur too stretched out?

I installed new double chainrings that are 2 teeth larger but have not lengthened the chain. It pedals fine in the bike stand but I've not ridden it yet.



bike in BIG-BIG gear

rbrides

Additionally, I seldom ride BIG-BIG, or even BIG-2nd gear to avoid cross chaining. Also, BIG-BIG is the same gear ratio as SMALL-5th gear so I prefer getting into the small ring before steeper climbs so I can more easily move up & down the cassette as needed. But, on the occassion that I might get into BIG-BIG, does this look advisable?

Moe Zhoost

Looks ok to me, but you are getting close to the limit. When you get around to replacing the chain you can reassess the need for an extra link or two. What does the small-small combo look like?

delbiker1 

I would say close to the limit, but ok. Even if you try to avoid the big-big, it is prudent to have the capability to get there. Very bad things can happen with an accidental shift into big-big without enough chain length. I like the smallest chain you can get away with in the big-big theory.

rbrides

Thanks Moe and Delbiker 1,

Finally found my Big Blue Book of Bike Repair from Park Tools.

In their chapter on chains is a pic with the caption "double bends at each pulley indicate adequate chain length".

It SEEMS I have enough chain length, but I always appreciate the knowledge folks here on Bike Forums provide.

All other input is welcomed.

cxwrench

Post a photo in small/small.

woodcraft

It's fine. That's how it's supposed to look by big/big + 1" chain sizing.

Bill Kapaun

This is a quick in situ test so see if you have some slack.

79pmooney

If it were me, I'd consider easing the derailleur forward a turn or two on the B-screw, (Small screw on the top rear of the derailleur that engages the hanger.) I'd do that then check for smooth shifting. (Shifting should theoretically be a touch worse but I'd like the piece of mind knowing that a clumsy shift into the gear I'm not supposed to use at a mountain top wasn't going to leave me stranded. Reduced mental capacity at mountain tops is a problem I've wrested with for years. Doesn't help that I seek out the opportunities to achieve it.)

Rogerogeroge

What does that show, other than your chain needs to be cleaned and lubricated?

cxwrench

It's how you check to see if you can remove a link safely.

Bill Kapaun

So someone with the slightest mechanical sense can see how much slack is left.
Since an addition of 4T ring/cog size means 1" more chain needed, one with the slightest sense of arithmetic can do the calculation to see if they can go to a larger cog without adding chain or not.

To infer my chain needs lube is simply a stupid assumption.

csport

Correct me if I am wrong, the big-big + 1 size is needed for shifting into the big-big combination. The extra two half-links are needed for the chain to climb over the teeth of the big chainring or rear cog. Otherwise the chain will jam during shifting, mangle the rear derailleur and destroy the hanger -- bad things delbiker1 mentioned. If you can shift into the big-big on the stand without the chain jamming you are probably OK.

canklecat

I always measure the chain long enough to safely run in the big/big combo. Because I know that on some ride when I'm hammering up a climb to snag a PR, or to keep up with a stronger group, I'm gonna unintentionally shift into the big cog before remembering to shift to the little chainring. If it's noisy outside I probably won't hear the telltale sound of cross-chaining. Or I may not want to risk dropping the chain by shifting down to the smaller chainring during a climb. I've done it before under duress and I'll probably do it again.

I've cut chains specifically for certain cassettes and freewheels, because the chain I cut for, say, a 13-24 may not be safe with the 13-28 I plan to use for a route with more climbs. Ditto, switching between 38, 39 and 42T small and 50 or 53T big chainrings. I try to remember to label the chains in a ziplock bag for next time.

It's less crucial on my bikes with long cage rear derailleurs, but I know I'm pushing the limits of some older short cage RDs already when I use 28T big cogs on the cassettes/freewheels.

So far I haven't killed a rear derailleur or ruined a chainstay from chain slap. Although I do need to replace the old tape over my Ironman's chainstay.

rbrides

Thanks all for the input. I'm good to go. No pics of small-small but on a ride with some very experienced riders (decades) they too opined it was all good. Approx 60 miles on two rides since my original post and not a single problem.