# 11-25 to 11-28 question



## TiBike (Aug 2, 2004)

I would like to switch the 11-25 cassette on my R3 to an 11-28. Will I need to lengthen the chain? Does the rear derailleur have enough play to accommodate that change? Thanks!


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## Merc (Oct 9, 2011)

I think you will be okay.


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## Rajarajan (Aug 6, 2008)

I bought an S3 last month. It came with a 11-25 that I had the store change to 11-28. It was a quick change with no extra links needed for the chain. So you too should be good to go.


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## nhluhr (Sep 9, 2010)

It depends on how your chain was initially sized. If all parts are in-spec (meaning your rear derailleur is intended for an 11-28 cassette) then you can shift your current setup to big-big then fold one pair of half-links over on themselves to simulate a 2-tooth increase in chain tension (which is more than the 11-25 to 11-28 would actually require since only half the actual tooth increase is engaged, the 'calculated' length is 1.5 links longer than before). If the tension arm of the rear derailleur still can handle it, then you're good.


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## TmB123 (Feb 8, 2013)

I know there is often much debate about the "correct" way to size a chain, but for what it's worth, Shimano's official direction is to add two links when going to 28T and above (assuming the correct chain length was used in the first place I guess). 
Also the way to size the chain changes.

http://si.shimano.com/php/download.php?file=pdf/dm/DM-RD0003-06-ENG.pdf (check out page 6)


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## TiBike (Aug 2, 2004)

TmB123 said:


> I know there is often much debate about the "correct" way to size a chain, but for what it's worth, Shimano's official direction is to add two links when going to 28T and above (assuming the correct chain length was used in the first place I guess).
> Also the way to size the chain changes.
> 
> http://si.shimano.com/php/download.php?file=pdf/dm/DM-RD0003-06-ENG.pdf (check out page 6)


Would it matter (in terms of chain length) that the R3 runs a 52/36 up front?


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## TmB123 (Feb 8, 2013)

I don't think so as the same could be said for a 50T chainring or 53T chainring. I believe it is more to do with how much slack or tension the dérailleur can handle between the large and small cogs on the cassette.

i run an 11 speed 52/36 x 11-28 setup and did it the way Shimano reccomended - Big Big and add 2 links. I'm not sure how much tollerance there is in number of links before you start to see issues. That could possibly depend on the range of the cassette you are trying to cover.


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## Lombard (May 8, 2014)

TiBike said:


> I would like to switch the 11-25 cassette on my R3 to an 11-28. Will I need to lengthen the chain? Does the rear derailleur have enough play to accommodate that change? Thanks!


You did not say which rear derailleur you have. It would depend on that too. The biggest problem you might have is if your RD isn't designed to go to that large a cog, the pulley will clash with the largest cassette cog and make an annoying "motor boat" noise. You can often solve this problem by adjusting the B-screw. It's worth a try and if it doesn't work, you can always replace the RD if finances allow.

As far as your chain, as long as you can go largest/largest without the chain binding, you are good to go.

HOWEVER, how many miles do you have on your existing chain? Unless your chain is relatively new as in less than 500 miles, you are very foolish to replace a cassette without replacing the entire chain. Chains stretch over their life. If you put a new cassette on and use a worn chain, you will eat up the cassette a lot faster. As one bike mechanic once put it, "your chain and cassette eventually marry each other".


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