# Cassette options



## gp257 (Oct 27, 2010)

Hi , I am having problems with a new set wheels (DT swiss RR465 w/ 240 hubs) I own a 2010 Synapse with compact gearing 50/34 and 12-25 cassette. my new wheels have a 11-28 and my RD is not making it to the 28 cog. Another forum says that there might be a spacer missing behind the cassette others say I will need to adjust the RD evey time ( don't like that) and one said that my RD my not be suited for a 28 cog.
Does anybody with some insight of a 2010 Synapse with compact gearing (12-25) and has tried or knows if it can handle a 11-28 cassette please let me know if it will work.
Thanks for all help !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!


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## coachstevo (Sep 11, 2009)

It is BS that your rear derailleur won't handle a 28- shimano's only made a 27 until recently so their literature all said max 27 (but even older ones could hit 30 easy)

I swap between a 26, 28 and 32 cassette- no adjustment issues.
if the RD is hitting on the cog, then adjust the B-screw to give yourself the clearance- you won't need to adjust that to switch back

if the RD isn't hitting the cog, then just adjust so it makes it, then try the smaller cassette - chances are you won't need to adjust


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## kneejerk (Feb 2, 2007)

can depend on what rear derailleur you have on there? 
a 28 is a stretch for any Shimano road rear derailleur, although they seem to be specing bikes with them nowadays,
could just be an adjustment issue, where the rear derailleur "L" screw was already too far in with the 25 but it allowed it to shift there because the cog is smaller (in comparison),
the other possiblity is that you will need to lengthen your chain a few links to accomodate the bigger gear range,


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## coachstevo (Sep 11, 2009)

28 isn't a stretch for Shimano...their literature just says that because they only built a 27 rear cassette until recently. I've used 28, 30, and 32s for years all with Shimano RD- 6500, 6600 and just recently a new 6700.

The H/L adjustment shouldn't change as that has to do with the spacing of the gears- that doesn't change when you change cassettes. If it looks like it does then there's a problem, probably a missing spacer all the way on the inside of the hub.

You can usually go all the way up to 32 without issues- the only limiting factor might possibly be the B screw adjustment (since that relies on a frame component)- worst case if you need more adjustment there to clear the pulleys on the big cog is you swap the screw around (you get an extra mm or two from the screw head)


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## s.mousseau (Oct 15, 2009)

The derailler maximum is due to its ability (or lack of) to take up the chain slack. It shouldn't affect it from physically clearing the large cog. see http://sheldonbrown.com/gloss_ca-g.html#capacity


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## ph0enix (Aug 12, 2009)

gp257 said:


> Hi , I am having problems with a new set wheels (DT swiss RR465 w/ 240 hubs) I own a 2010 Synapse with compact gearing 50/34 and 12-25 cassette. my new wheels have a 11-28 and my RD is not making it to the 28 cog. Another forum says that there might be a spacer missing behind the cassette others say I will need to adjust the RD evey time ( don't like that) and one said that my RD my not be suited for a 28 cog.
> Does anybody with some insight of a 2010 Synapse with compact gearing (12-25) and has tried or knows if it can handle a 11-28 cassette please let me know if it will work.
> Thanks for all help !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!


The hubs are probably different between the new and the old wheels so the cassette might be sitting in a slightly different spot on each. If that's the case, you will need to readjust the deraileur after you swap the wheels. You might want to ask about the specific mix of components you're running (RD, wheels and cassette) in the wrenching forum. It's possible that someone has experience with that exact combo.


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## alanw2007 (Jan 4, 2009)

Is your chain long enough for the 28t cog? It will need another couple of links compared to the 25t.
If all the other gears are indexing correctly, that indicates the two cassettes are sitting in the same position relative to the frame, which is what you want.
As also posted here, you may need a few turns on the b-tension screw to pull the derailleur farther away from the cassette. This will give the space needed between the large 28t cog and the top jockey wheel.


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## bon_gabs (Feb 2, 2010)

how come shimano ended up making a RD (RD-5700) with short and long cages options? is the short compatible with 11-28 cassette? whats the difference between short and long? thanks.


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## kneejerk (Feb 2, 2007)

bon_gabs said:


> how come shimano ended up making a RD (RD-5700) with short and long cages options? is the short compatible with 11-28 cassette? whats the difference between short and long? thanks.


The different cage lengths are to accomodate a larger range of gear teeth on the crank set. Since both rear derailleurs use the same otherwise construction the cassette compatability is the same (for the most part).


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## kneejerk (Feb 2, 2007)

s.mousseau said:


> The derailler maximum is due to its ability (or lack of) to take up the chain slack. It shouldn't affect it from physically clearing the large cog. see http://sheldonbrown.com/gloss_ca-g.html#capacity


Actually I think you are interpreting that a bit wrong. The rear derailleur is definitely designed for a gear range. How much it can handle can be fudged a bit with frame mounting point modification as another has noted but, otherwise it is as designed.

Here is a quote from the Sheldon Brown article you linked: _"Rear derailers are also commonly designed for a particular maximum size of rear sprocket. If you exceed this size by too much, the jockey pulley may rub against the sprocket when using the lowest gear. 

Rated maximum rear sprocket size, however, is also commonly much lower than what actually works. For instance, Shimano's models designated as "road" derailers are generally listed for a "maximum" sprocket of 27 teeth...because 27 teeth is the largest size that they make in a designated "road" cassette. However, in almost all cases, these derailers, even the short-cage models, will handle rear sprockets as large as 30 teeth in practice. (This somewhat depends on the design of the frame's derailer hanger, so once in a while you will find a particular installation where you can't use a 30, but I've never seen one where a 28 wouldn't work.) "_


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## alanw2007 (Jan 4, 2009)

Long cage is really to cope with a triple crank.
Short cage should work with 11-28 cassette and 50/34 crank. Current 105/Ultegra/Dura Ace is designed with this as its maximum gear range.
Compact cranks have maximum 16 teeth difference between the rings. Triples have more (22 teeth difference typically). This is such a large difference that a short cage mech can't take up the slack in the chain when on small/small, if the chain is long enough for big/big.


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