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Chain Length Question
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I recently decided to bring my road bike into the 2010s with an 11 speed upgrade. I purchased new Ultegra (R8000) levers along a FD, a RD, chain, and new cassette. When looking at the documentation for setting up proper chain length it said to put the chain around the biggest chain ring and biggest cog, see how the ends meet and add 1 - 3 links. I did that no problem but the chain is so short that when it runs through the RD I can't physically get it on the large chain ring and largest cog. I know cross-chaining like this while riding is a no no, I've just never not been able to physically shift to the two extremes. Did I do something wrong? Should I have run the chain through the RD as well when trying to determine the correct length? If I still have the length of chain I removed can I put it back on the end with a chain tool and 11 speed pins? Many thanks for any advice.
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Re: Chain Length Question [fletcherandrew] [ In reply to ]
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when I want good info I go to Park Tool:
try this:
https://www.parktool.com/.../chain-length-sizing
also depends on your rear derailleur cage length (ie long cage gives more range vs short cage)
hope this helps.
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Re: Chain Length Question [fletcherandrew] [ In reply to ]
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fletcherandrew wrote:
see how the ends meet and add 1 - 3 links. I did that no problem
Add an inch (2 links) and always round up. Never add just one link.

If the jockey wheel isn't too close to the cassette when you're in the big cog, you could give yourself a bit more room by backing off the b-screw, which will rotate the derailleur forward and cause the chain's path to be just a tiny bit shorter.

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Should I have run the chain through the RD as well when trying to determine the correct length?
No, the whole idea of the "big+big plus an inch" method is to account for the extra chain length needed by the rear derailleur.

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If I still have the length of chain I removed can I put it back on the end with a chain tool and 11 speed pins?
If you have one of the special chain pins that's specifically designed for joining a Shimano 11-speed chain, I don't see why not. Alternately, you can use a second quick link.

Don't just use a pin that you removed from the chain, though. The narrow outer widths of modern chains mean that pins are designed to sit very exactly flush with the plates. There's very little margin for error, and exactly restoring the pin's placement and shape isn't something that can reasonably be done with a chain tool. It can be worth trying if you break a chain on a ride and all you have is a chain tool, but even if it works, you're creating a weak spot in the chain that should not be trusted for long-term use.
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Re: Chain Length Question [HTupolev] [ In reply to ]
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HTupolev wrote:
fletcherandrew wrote:
see how the ends meet and add 1 - 3 links. I did that no problem

Add an inch (2 links) and always round up. Never add just one link.

If the jockey wheel isn't too close to the cassette when you're in the big cog, you could give yourself a bit more room by backing off the b-screw, which will rotate the derailleur forward and cause the chain's path to be just a tiny bit shorter.

Quote:
Should I have run the chain through the RD as well when trying to determine the correct length?

No, the whole idea of the "big+big plus an inch" method is to account for the extra chain length needed by the rear derailleur.

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If I still have the length of chain I removed can I put it back on the end with a chain tool and 11 speed pins?

If you have one of the special chain pins that's specifically designed for joining a Shimano 11-speed chain, I don't see why not. Alternately, you can use a second quick link.

Don't just use a pin that you removed from the chain, though. The narrow outer widths of modern chains mean that pins are designed to sit very exactly flush with the plates. There's very little margin for error, and exactly restoring the pin's placement and shape isn't something that can reasonably be done with a chain tool. It can be worth trying if you break a chain on a ride and all you have is a chain tool, but even if it works, you're creating a weak spot in the chain that should not be trusted for long-term use.

Also, don't use a replacement pin on a link that has had a replacement pin used in it before; choose a different link. With 11/12spd chains the margins for error are much smaller.

As for what could go wrong: https://www.youtube.com/...QY6f_9RbpQ&t=340
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Re: Chain Length Question [fletcherandrew] [ In reply to ]
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Big, big, and add two links (one inch).

What cassette ratio do you have?

Is your rear derailleur a GS or SS?
Last edited by: jimatbeyond: Sep 3, 20 14:43
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Re: Chain Length Question [fletcherandrew] [ In reply to ]
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I might take shit for this but oh well. Just my personal experience over the years. I've run into this several times in the past, while swapping to larger font rings and/or cassettes, while using the existing chain. So far, in every case, it's always worked fine on the small front- big rear, so I've never worried about it. In my over 40 years of riding, I've never experienced a situation where I needed to cross chain big front-big rear, and have never done it on a ride or in a race. In your shoes, if all is working and shifting well, and small front-big rear is working fine, I would ride on and not worry about it. If you're cross chaining from big front, to the biggest 3-4 cogs in the rear, you're wearing stuff out faster than you should anyways, and it's a good habit to get out of.

Athlinks / Strava
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Re: Chain Length Question [fletcherandrew] [ In reply to ]
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I always feed the chain around small/small and through the derailleur then make the chain is short enough to put tension on the rear derailleur and long enough to go big/big on the biggest cassette you own.

By doing that the chain is always long enough for the capacity of the derailleur.
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Re: Chain Length Question [Dean T] [ In reply to ]
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Dean T wrote:
In my over 40 years of riding, I've never experienced a situation where I needed to cross chain big front-big rear
It's sometimes convenient to be able to avoid bailing to the small ring when you know you'll soon after need to get back into your high gears.

But also significantly: what's logical, what you need, and what people do when they're gasping for air and their head is spinning six minutes into a hard climbing effort can all be very different things. This really just depends on the person's subconscious shift habits: some people won't go big-big even on bikes where it works smoothly, other people will sometimes accidentally go big-big on bikes where it rips the derailleur off even though they've told themselves not to do it.
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Re: Chain Length Question [HTupolev] [ In reply to ]
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HTupolev wrote:
Dean T wrote:
In my over 40 years of riding, I've never experienced a situation where I needed to cross chain big front-big rear
It's sometimes convenient to be able to avoid bailing to the small ring when you know you'll soon after need to get back into your high gears.

But also significantly: what's logical, what you need, and what people do when they're gasping for air and their head is spinning six minutes into a hard climbing effort can all be very different things. This really just depends on the person's subconscious shift habits: some people won't go big-big even on bikes where it works smoothly, other people will sometimes accidentally go big-big on bikes where it rips the derailleur off even though they've told themselves not to do it.

This is a good point.
I don't go big-big usually, and have a fair amount of 'mechanical sympathy' when riding.. But... once when out on an mtb ride... I'd had to shorten the chain after a some damage to a link (maybe on a rock). No prob... i don't go big-big. Until I did some random shift - maybe dropping to the little front ring + going to big at the back for a steep climb... and everything jammed up. The chain got onto the big ring at the back before dropping off the big at the front. Result a totally jammed up drive. And with so much locked in force in the chain, I couldn't just remove the rear wheel to sort it out.
(Cue having to break the chain yet again trailside, and then leaving it in the front granny ring for the remainder of the ride to avoid a repeat).
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Re: Chain Length Question [HTupolev] [ In reply to ]
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HTupolev wrote:
Dean T wrote:
In my over 40 years of riding, I've never experienced a situation where I needed to cross chain big front-big rear
It's sometimes convenient to be able to avoid bailing to the small ring when you know you'll soon after need to get back into your high gears.

But also significantly: what's logical, what you need, and what people do when they're gasping for air and their head is spinning six minutes into a hard climbing effort can all be very different things. This really just depends on the person's subconscious shift habits: some people won't go big-big even on bikes where it works smoothly, other people will sometimes accidentally go big-big on bikes where it rips the derailleur off even though they've told themselves not to do it.

That's mainly why I set up for big/big as well
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Re: Chain Length Question [jaretj] [ In reply to ]
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jaretj wrote:
HTupolev wrote:
Dean T wrote:
In my over 40 years of riding, I've never experienced a situation where I needed to cross chain big front-big rear

It's sometimes convenient to be able to avoid bailing to the small ring when you know you'll soon after need to get back into your high gears.

But also significantly: what's logical, what you need, and what people do when they're gasping for air and their head is spinning six minutes into a hard climbing effort can all be very different things. This really just depends on the person's subconscious shift habits: some people won't go big-big even on bikes where it works smoothly, other people will sometimes accidentally go big-big on bikes where it rips the derailleur off even though they've told themselves not to do it.


That's mainly why I set up for big/big as well

Yep. Going big-big is something you shouldn't consciously do. But the appropriate punishment for doing it accidentally is some chain rub and a loss of efficiency, not having your RD ripped off.
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Re: Chain Length Question [jimatbeyond] [ In reply to ]
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Thanks to everyone for their recommendations.

Jim - 53/39 on the front with 12/25 | 12/28 on the back with a GS cage.
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Re: Chain Length Question [fletcherandrew] [ In reply to ]
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Whatever you do, don't do what I did, is that I accidentally put swapped my road bike and TT chains after a wax; one is significantly shorter than the other. What ends up happening with a way-too-short chain is that you shift to an unfortunate big-ring combo, and then the chain makes the shift after a forceful pedalstroke, but then gets stuck and not only can you not pedal (it grinds instead!) but you can't shift back out of it since it's locked onto that gear combo. I had to stop, remove the back wheel, and manually place the chain back on the smaller cogs to get going again.
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Re: Chain Length Question [lightheir] [ In reply to ]
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Luckily enough I figured out that same thing while I had the bike in the work stand. Somehow I managed to be able to back pedal and the chain reset.
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