Shadco 

Not that I would ride big big but I would like an opinion.





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FBinNY 

The chain exceeds the ABSOLUTE MINIMUM length.

However, the drive train might perform better with if were a bit longer.

Bill Kapaun

Put it on BIG:BIG and see if you have at least 1" slack without forcing it. (you'd probably be ok with 3/4")

Moe Zhoost

At the limit. I'd opt for a link-pair longer.

pdlamb

Nobody ever wants to ride big-big, but most everybody does at some point.

I agree that's right at the edge. Probably won't hurt anything, but you may hear some extra noise reminding you to shift the front.

Shadco 

I have a new chain coming anyway, that chain was from a 53/39 ==> 13/26 cassette to a 50/34 ==> 13/29 cassette and I fit it just to see how close it was.

It failed the 1” slack test miserably.

Sucks getting old but I expect granny gears to help.

Thanks for the input.

I’m going to try 2 link pairs longer but I bet that will be too slack small / small.

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Moe Zhoost

Good plan. If it turns out ok, you're done. If a bit slack, then cut one link pair and you're done.

rydabent

If you can still push up on the derailer and have the chain go slack, the chain is long enough.

veganbikes

I would lengthen it a touch. It is pretty short even if yes we do try and avoid big big and little little I would rather have an extra couple links just in case.

grumpus

You wouldn't want it any shorter, but as long as it shifts cleanly on and off the large sprocket it should be fine. I'd rather have the chain a bit short on big/big than a bit slack on small/small, as long as it runs OK.

Lombard

As long as it turns freely without any binding, it's fine.

Pratt

When adding, won't he then have to check little-little?

Steve B.

This

Shadco 

A link pair longer with a new chain worked out perfect.

Someone got really tired supervising and inspecting.




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Camilo

Yes, if he adds a link and the RD can still take up the slack of small-small, it is OK.

That said, I think the original chain length posted is OK. There are bends around the jockey wheels so it's not too tight.

FBinNY 

BITD sizing chains trial and error wasn't an issue. Cut it short and decide you made a mistake? No issue, take out the chain tool and splice a few links back in.

However, these days, lengthening a chain is problematic, so one has to get it right the first time, or if using a reusable connector, start long then cut shorter if needed to. Non-reusable connectors still allow a chain to be cut again, with the only issue being the cost of a new link.

So, for the O, and anyone else sizing a chain, here's my process which ensures I won't be doing it twice.

1- measure for MINIMUM length by threading the chain and looping big/big, pulling the lower loop forward until the RD is near max. Count the number of overlapped links, to determine how many you could cut off if you chose to.

2- move to small/small and pull the lower loop forward until the RD cage is pulled off the rewind stop. Count the overlapped links to know how many need to be cut off.

3- Now that you know the most and least to cut, you have the freedom to pick within that range. Owing to a habit I developed BITD when stiff links were an issue, I generally cut the chain the longest that is OK. This allows (allowed) the option of cutting out a damaged link in the field and still be OK.

Lastly, if you have an old reusable connector (even if not suitable for that chain) you can use it to double check the length by running through the gears before finalizing the length.

Otherwise, keep in mind the carpenter's lament, "I cut it twice, and it's still too short".

79pmooney

Two points here. 1) the chain goes tightest climbing onto the cog, then settles down in between the teeth. So it can run fine in the large-large and still be problematic while shifting. When I've had things go wrong, it's always been during the shift, not JRA.

2) A too loose small-small is rarely an issue beyond bad sounds (of the chain rubbing itself at the folded back lower idler pulley or dragging on the chainstay) and paint wear on the chainstay. I've set up triples many times with small-small chain rub and felt completely free to use that combo on long climbs that leveled out for a while and simply did not want to do a pair of double shifts. By contrast, big-big issues have me reaching into my pockets - for the cell phone now and wallet later.

Lombard

Being able to climb up to the largest cog can easily be tested in the stand while running through the gears. If it doesn't bind, it's fine.

Small-small should never go slack. There sound always be a little tension.

FBinNY 

Never is too big a word here. Obviously, being to run small/small without slack, or the chain doubled back on itself is SOP, but there are situations where It's the best compromise.

While needing to be OK big/big is critical because of the consequences small/small slack has no consequences.

So running an over long chain makes sense if the gear range exceeds RD capacity. It's a common issue for road triples using a "bail out" granny.

Lombard

If it becomes an either/or thing, you need to get the proper RD. Otherwise it is a hack at best.

FBinNY 

Your hack is my reasoned choice

Back in the Bronze Age, I was touring using a Record 10s (5×2) system with a wide freewheel and half step gearing. It was fine for most rides, but when planning for some serious climbs, I opted for a different crank, using the same steps, plus a granny.

The arrangement allowed me to enjoy the gearing that served me well, with some bonus low end options for when I needed them.

Shadco 

I would love to find a serviceable Chorus or Record medium cage RD in 10 speed but so far my searching has yielded nothing. I’m right on the edge with short cage, 50/34 crankset, and 13/29 cassette. The gearing works well for where and how I ride and shifting is good.

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Lombard

Not sure about Campy, but Shimano is quite conservative with their ratings. Shimano claims their mid cage derailleur only works up to a 32T cog, but I run an 11-34T with a 34/50 compact crank and it works perfectly - no binding in large-large, no slacking in small-small.

DaveSSS 

I exceed the stated wrap capacity of SRAM AXS RDs and don't care if the chain is slightly loose in the small ring and next to smallest sprocket. The RD doesn't even allow shifting to the small/small. I use the little ring for steep climbs and don't use it much more than necessary. I have three bikes with the same 415mm chain stay length. I like using the chain length formula to know just how much excess length I have and I know that each tooth needs 1/4 inch of chain. With a 46/30 and a 10-36 cassette, the minimum length is 54.18 inches. A 54 will work, since having a full inch of excess to go through the RD isn't necessary, but I use a 55 inch length. I can change to a 48/31 crank and/or a 10-33 cassette with no problem.

To get the length, add the big ring and largest sprockets and divide by 4. Add twice the chain stay length. Add 1 inch. Chain lengths are always a whole number in inches. If the length is over a whole number by less than 0.25 inch, the shorter length may work, but it's always best to round up.
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smd4

I don't know about Campagnolo, but sizing chains for Shimano drivetrains BITD was never "trial and error." you simply followed their chain installation instructions.