# 11-25 to 11-28, do I need a longer chain



## caak (Jun 15, 2009)

G'day,

So I want to climb a little easier and run a 11-28 cassette. I currently have a 11-25.

Will this really make much difference, if so do I need a new longer chain as well?


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## brianmcg (Oct 12, 2002)

It will make a difference, and no you do not need a longer chain. Needing a new one would be dependent on wear.


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## wim (Feb 28, 2005)

Depends on how your chain was cut for length. Install the 11-28 cassette and on a stand, carefully shift to see if your drivetrain can still handle the biggest chainring-biggest cog (28) combination. If not, you definitely need a longer chain.


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## Johnpembo73 (Jul 28, 2011)

Will this mean as well he might need a new rear derailleur, if he has a standard short one installed on bikes with 11-25?


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## rbart4506 (Aug 4, 2004)

He should not need a new RD...It should be able to handle the chain wrap....

I swap from an 11-25 to 11-28 without any issue...


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## caak (Jun 15, 2009)

just read my bike spec has a 12-25, does that make any difference?

shifters	Shimano 105
front derailleur	Shimano 105
rear derailleur	Shimano 105
brakes	Shimano 105
brake levers	Shimano 105
cassette	Shimano 105 12x25, 10-speed
chain Shimano 105
cranks	Shimano 105, 34/50


thanks for the info so far.


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## Optimus (Jun 18, 2010)

I believe 2 teeth = 1/2 link of chain, so it depends on how the chain was cut originally, if they factored in any extra links, if not, then yes a new chain is in store.


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## wim (Feb 28, 2005)

caak said:


> just read my bike spec has a 12-25, does that make any difference?


All that means your bike came that way. You could put on an 11-32 cassette if you wanted, providing you make the needed changes in chain length and rear derailleur model.

I'm assuming you have the RD-5700 "10-speed" 105 rear derailleur, most likely the SS model (short cage). For that derailleur, Shimano lists the 28 cog as the largest possible cog. Total capacity is listed as 33 teeth. To figure total capacity, add the difference of the rear to the difference of the front, like this: (28-11) + (50-34) = (17) + (16) = 33. You're good to go, theoretically.

But what people are saying is this: if someone at the factory or a bike shop cut the chain as short as possible (not likely, but you never know), the change from the 25 to the 28 can get you into real trouble if you're cranking in the big chainring. That's why I suggested to make a test.


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## Kerry Irons (Feb 25, 2002)

*Cutting it close*



Optimus said:


> I believe 2 teeth = 1/2 link of chain, so it depends on how the chain was cut originally, if they factored in any extra links, if not, then yes a new chain is in store.


It would have to have been really "at the limit" in order for a 3 tooth difference to have required a new chain. If someone set up the chain on a 12-15 that close to the edge, it would be both a surprise and a very poor reflection on whoever installed the chain.


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## ejprez (Nov 9, 2006)

I think a longer chain is in order if you cross chain with big ring and big cog. I've seen that so many times on the local novice group rides. The rear derailleur cage is so far pulled forward that they could use a couple links, If the keep that up it will lead to premature ware and if they are rally unlucky the rear derailleur will fail. Your chain may already be the right length, but if not then add 2-4 links.


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## rgordin (Oct 22, 2010)

Don't forget to check your RD adjustment (the "B" screw) to make sure you have room between the largest cog and the RD pulley.


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## redlude97 (Jun 29, 2010)

Kerry Irons said:


> It would have to have been really "at the limit" in order for a 3 tooth difference to have required a new chain. If someone set up the chain on a 12-15 that close to the edge, it would be both a surprise and a very poor reflection on whoever installed the chain.


I'm certainly not a mechanic so I don't know how they commonly set up chain lengths, but wouldn't you want your chain to be as short as possible? As in just barely able to shift into the big/big configuration since it isn't a useable gear anyways? I used the big/big+2 links method to size my chain and I don't know if I could use a larger cassette with it without needing a longer chain if I decided to make that change.


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## wim (Feb 28, 2005)

redlude97 said:


> I'm certainly not a mechanic so I don't know how they commonly set up chain lengths, but wouldn't you want your chain to be as short as possible? As in just barely able to shift into the big/big configuration since it isn't a useable gear anyways? I used the big/big+2 links method to size my chain and I don't know if I could use a larger cassette with it without needing a longer chain if I decided to make that change.


Why as short as possible? The only "advantage" I can see would be a few grams saved. I like to cut my chains as long as possible, meaning cut so it'll almost go slack in the rarely-used small-small combo. I just like the certainty of being able to briefly use the big-big combo (which I do quite often) without a mechanical, and there's a little less friction because of less tension from the derailleur cage- and housing spring when cranking in the big ring on the bigger cogs in rear.

But it's not a big deal one way or the other to me. If someone would cut my chain as short as possible, I'd wait until the next chain change to rectify the situation.


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## redlude97 (Jun 29, 2010)

wim said:


> Why as short as possible? The only "advantage" I can see would be a few grams saved. I like to cut my chains as long as possible, meaning cut so it'll almost go slack in the rarely-used small-small combo. *I just like the certainty of being able to briefly use the big-big combo (which I do quite often) without a mechanical,* and there's a little less friction because of less tension from the derailleur cage- and housing spring when cranking in the big ring on the bigger cogs in rear.
> 
> But it's not a big deal one way or the other to me. If someone would cut my chain as short as possible, I'd wait until the next chain change to rectify the situation.


Yea I'm not talking about not being able to use the big/big combo. Using the big/big+2 makes that combo still totally useable. I just don't see the reason for having a longer than necessary chain if you don't plan on changing the cassette. Also, when in the big ring and second largest cog the RD cage angle isn't that extreme. So what method do you use to set up your chain length then?


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## OldChipper (May 15, 2011)

Should be fine, but check RD extension with 28 on to be sure. I switch between 11-25 and 11-28 all the time, but chain was sized for 28 to start.


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## intence (May 23, 2010)

What's the "longest" that a chain can be cut? Is there some type of formula? (Big Big + x?)


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## wim (Feb 28, 2005)

redlude97 said:


> Yea I'm not talking about not being able to use the big/big combo. Using the big/big+2 makes that combo still totally useable. I just don't see the reason for having a longer than necessary chain if you don't plan on changing the cassette. Also, when in the big ring and second largest cog the RD cage angle isn't that extreme. So what method do you use to set up your chain length then?


Agree with your reasoning, so let's just say I feel I'm running the drivetrain with as little frictional losses as possible if the chain is as long as possible. If you ever adjusted a track bike chain, you now how the loosest but still safely running chain gives you the least amount of drag.

The method is simple: chain in the small-small combo, then pull the ends together and cut / join at the point where the rear derailleur cage is just beginning to put a slight amount of tension on the lower run of the chain. The chain should not contact the cage, of course. (See area in the lightenend circle). Hope that answers intence's question as well. Photo's my Surly Pacer in the small-small (42 x 12).


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## redlude97 (Jun 29, 2010)

wim said:


> Agree with your reasoning, so let's just say* I feel I'm running the drivetrain with as little frictional losses as possible if the chain is as long as possible.* If you ever adjusted a track bike chain, you now how the loosest but still safely running chain gives you the least amount of drag.
> 
> The method is simple: chain in the small-small combo, then pull the ends together and cut / join at the point where the rear derailleur cage is just beginning to put a slight amount of tension on the lower run of the chain. The chain should not contact the cage, of course. Hope that answers intence's question as well. Photo's my Surly Pacer in the small-small (42 x 12).


Is this true though? Intuitively to me those extra bends in the chain add more friction, but I don't have any source to back that up. With the derailleur more stretched out I would think that the chain travels smoother through the cogs.


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## wim (Feb 28, 2005)

redlude97 said:


> Is this true though? Intuitively to me those extra bends in the chain add more friction, but I don't have any source to back that up. With the derailleur more stretched out I would think that the chain travels smoother through the cogs.


Good question, and I don't have an answer. When pedaling a bike on the stand, I can certainly see, feel and hear more and more friction being added into the drivetrain as the derailleur cage winds up / stretches out more and more. And apart from "safe big-big," that's really all I base my "longest possible" preference on.

The angle a chain link forms with the next one matters to some degree, you're right. But it's not the "bending action" at the pin. Because a link in itself cannot bend, it tugs at the next link not in a straight line, but at an angle. (Think of a freight train going around an extremely tight circular track.) The yellow arrows on the illustration show force magnitude and force vector of a new chain chain driving a new cog. With worn components, it gets even more complex.


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## Kerry Irons (Feb 25, 2002)

*History*



redlude97 said:


> Is this true though? Intuitively to me those extra bends in the chain add more friction, but I don't have any source to back that up. With the derailleur more stretched out I would think that the chain travels smoother through the cogs.


The "longest chain possible" recommendation has been in place at least since the 1960s. Lower friction is the reason, but since I am not a mechanical engineer, I cannot explain why.


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## cxwrench (Nov 9, 2004)

intence said:


> What's the "longest" that a chain can be cut? Is there some type of formula? (Big Big + x?)


this has been discussed time after time...the way to get the safest/longest chain is the small/small method described by MikeT. that will work every time unless you are using a shorter cage derailleur than what the spec says will work.


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## AndrwSwitch (May 28, 2009)

Not a mechanical engineer yet, but I have a thought.

A shorter chain means more tension on the derailleur cage. More tension on the cage means more tension on the part of the chain below the chainstay. Friction is dependent on the force between two surfaces, so there'd be more friction in any moving joints in that part of the chain. I think the biggest effect would be where it goes on and off the jockey wheels, and the angle changes significantly.

I think real-world effect on the drivetrain would be negligible. But people spend a lot of money for negligible differences, so when one's available free - why not.

I haven't worked on track bikes much. But few things machined to be round are perfectly round, and mounted perfectly on perfectly centered axes. When a singlespeed is set up with a chain that's tight to begin with, there are often a couple of chainring/cog positions that are even tighter, due to something being out of round.


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## cxwrench (Nov 9, 2004)

AndrwSwitch said:


> Not a mechanical engineer yet, but I have a thought.
> 
> A shorter chain means more tension on the derailleur cage. More tension on the cage means more tension on the part of the chain below the chainstay. Friction is dependent on the force between two surfaces, so there'd be more friction in any moving joints in that part of the chain. I think the biggest effect would be where it goes on and off the jockey wheels, and the angle changes significantly.
> 
> ...


this is true on track bikes too. i don't think i've ever seen a bike w/ everything lined up perfectly so chain tension stayed constant. for track bikes it's always been 'loose if fast', so we set chain tension as loose as possible w/o the chain coming off. set the tension and then spin the wheel and push on the chain w/ your wrench. it's good when it just about comes off the chainring, but you can't push it over.


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## BergMann (Mar 14, 2004)

To the OP:
I switched both of my road bikes (59cm frames w/ 53x39 rings) from 11-25 to 11-28 cassettes two seasons ago.
I added one link to one of my near-new chains (had kept the spares after installing it myself), and cut another brand new chain to the same length.
Short cage derailleurs & chains are Dura-Ace 7800, and the new cassettes are 7900.
Everything runs perfectly: but you will need to be careful with your "B-screw" setting & get the chain length just right, especially if you're going to run an older Shimano derailleur made before the recent move to 28T+ cassettes.

As for the ongoing discussion about too short vs. too long, I've not only seen lab tests that confirm this (e.g. Tour Magazin in Germany) but 30 years in the school of hard knocks has taught me that too short = friction & too long = crappy shifting.

What is more, it's not just about the running friction of a too-short chain burning more watts (i.e. the "drivetrain losses" you read about in all the power training literature), it's also about it burning a hole in your wallet.

Not only will an unduly-short chain tend to wear out quicker, it will also significantly shorten the life of your derailleur's return springs (especially if you're a recidivist on the cross-chain gang), and your pulleys, rings & cassettes will burn up right along with that chain.

As for the "how long is too long" question posed above. Cut your chain way too long & you'll know it: shifting will be stupid-slow & vague. As mountain bikers (or anyone else running a triple) know, too much chain length not only makes for slow, sloppy shifting from the little ring, it also causes undue chain slap/drop/suck on rough terrain.

Bottom line: chains are cheap, cassettes are not. The OP should buy a new chain, cut it to the length indicated in the manuf. instruction booklet, and ignore the silly stuff about derailleur compatibility, as long as they have the sense not to ride completely cross chained.


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## caak (Jun 15, 2009)

Whoa.. Thanks for all the info. I am thinking of adding a wipperman link as well, to give the chain a little extra length. Then I will see how it runs.


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## cxwrench (Nov 9, 2004)

BergMann said:


> As for the ongoing discussion about too short vs. too long, I've not only seen lab tests that confirm this (e.g. Tour Magazin in Germany) but 30 years in the school of hard knocks has taught me that too short = friction & too long = crappy shifting.
> 
> 
> 
> As for the "how long is too long" question posed above. Cut your chain way too long & you'll know it: shifting will be stupid-slow & vague. As mountain bikers (or anyone else running a triple) know, too much chain length not only makes for slow, sloppy shifting from the little ring, it also causes undue chain slap/drop/suck on rough terrain.


can you explain to me how having a chain that is 'longer' rather than 'shorter' will slow down shifting? seems odd to me since rear shifting takes place at the upper pulley, and it really has no idea whether a chain is long or short, and front shifting takes place w/ tension on the upper run of chain, so length has no affect on this either.


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## alexcomp (Apr 11, 2011)

*11-28 Ultegra 6700 with RD 7800*

This is my maiden effort at building a bike up from scratch and I may have made mistakes. I have access to an RD 7800 but the Shimano specifications say that it will handle a maximum of a 27 tooth largest cog. Another specification that I had to look up was the maximum tooth capacity – defined as the difference in tooth count of the chain wheels plus the difference in tooth count of the smallest to largest cassette gear.

In my case, that would be 14, (50 X 39), plus 17, (11-28). for a for a total of 31. The 7800 short cage lists 29 teeth or less.

However.... I have noticed several posts indicating that Shimano is extremely conservative in these ratings and that other people have successfully used the RD 7800 with an 11 – 28 cassette. So maybe I will be okay but then another question arises.

I ordered a CN – 7901 DuraAce chain and what I received was marked as 112 links. There was also the possibility of chans with 114 links and 116 links. I hope that the fact that I am using a large granny will not put me into a situation where the chain that I have in hand is too short.

Reassurances or observations on these questions would be appreciated.


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## AndrwSwitch (May 28, 2009)

Double-check your description of your crank. It's pretty inconsistent.

I have a really wide-range drivetrain, used to be even wider. I have a road triple, and it shipped in the old 52-42-30 configuration. I was riding with a 12-27 cassette and the older 105-GS (forget what series exactly. Probably 5500 - the bike is a '99 model) mid-cage derailleur for a long time. I had no trouble clearing the 27t cog but I found that I had to size the chain really correctly or it would drag in small/small. Obviously it's bad practice to use that combination, but I prefer to set my bikes up so that I don't break them when I make the kind of mistake I've been known to at high effort.

More recently, as an experiment, I tried leaving the Tiagra 4500-GS rear derailleur on my 'cross bike when I installed an 11-32 cassette. Again, I was able to get the derailleur to clear the largest cog. I didn't try to make it work for the whole gear range because I already had a new derailleur and chain that were going on that bike, so I can't say if it would work for a wildly larger gear range than its rating. I actually think I might have gotten away with it. I think this is a little less applicable to your situation because I think Shimano is even more conservative with their inexpensive groups.

Anyway, my expectation would be that you'd have no trouble clearing a 28t cog, but you might have trouble with capacity. IMO, it's better for the chain to drag in small/small than to break in big/big, because if it drags, it makes an annoying noise and you shift to a less stupid combination, and if it breaks, you have to stop and fix it.

I wouldn't worry about the chain length if this is a racing bike. Mountain bikes, especially full-suspension, and touring bikes may sometimes need all the links. (And tandems and recumbents, obviously.) I usually still cut two link pairs off a new chain for my MTB, which doesn't exactly have short chainstays. So I'd expect you to be fine.


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