Bicycle Mechanics - Largest cassette I can use

Wondering what the largest cassette I can use with my Ultegra triple R.D. and triple crankset. I'm preparing to do some serious climbing and want more than a triple with a 12-26 cassette. Can I use up to a 32 tooth cassette without changing the rear der. since it's already a long cage?

Assuming this is 9-speed, the Ultegra RD design looks effectively the same as a DeoreXT, which can handle up to a 34T. Although Shimano has derated it to 27T max, I wouldn't hesitate to try the 32T or 34T.

You might also think about switching to a 24-tooth granny ring if conditions call for it. That doesn't cost much compared to a new cassette. Shimano XTR 7075 aluminum with nickel plating, $5 (http://www.cambriabike.com/shopexd.asp?id=24916) You'd want to keep an eye on whether your FD can handle that without the chain dragging in the tail of the cage, though.

Ooops, the above ring is a 26T (still a hot buy for $5). Here's some 24T ones: http://www.cambriabike.com/shopexd.asp?id=11671

Assuming this is 9-speed, the Ultegra RD design looks effectively the same as a DeoreXT, which can handle up to a 34T. Although Shimano has derated it to 27T max, I wouldn't hesitate to try the 32T or 34T.

You might also think about switching to a 24-tooth granny ring if conditions call for it. That doesn't cost much compared to a new cassette. Shimano XTR 7075 aluminum with nickel plating, $5 (http://www.cambriabike.com/shopexd.asp?id=24916) You'd want to keep an eye on whether your FD can handle that without the chain dragging in the tail of the cage, though.

Ooops, the above ring is a 26T (still a hot buy for $5). Here's some 24T ones: http://www.cambriabike.com/shopexd.asp?id=11671

the ultegra won't handle a 34-tooth cog. i think 30 would be the max. i know for a fact that the DA long cage will only take a 30-tooth cog (on my bike anyway). you need a mega-range derailleur if you want to use a 34-tooth cog and i believe that would be an MTB derailleur.

ed rader

the ultegra won't handle a 34-tooth cog. i think 30 would be the max. i know for a fact that the DA long cage will only take a 30-tooth cog (on my bike anyway). you need a mega-range derailleur if you want to use a 34-tooth cog and i believe that would be an MTB derailleur.

ed rader

As with most things bicycle, I'd say try the long cage with a 32 or 34 tooth cog first. You might be suprised. I've run 30 tooth cogs on a short cage Ultegra before without ill effect. I'd suspect that a long cage would be able to handle the chain wrap quite well. Put on the cassette and put it on a work stand first. If it shifts funky, start looking for a new rear derailer. If it shifts nice and smooth, save your money.

As with most things bicycle, I'd say try the long cage with a 32 or 34 tooth cog first. You might be suprised. I've run 30 tooth cogs on a short cage Ultegra before without ill effect. I'd suspect that a long cage would be able to handle the chain wrap quite well. Put on the cassette and put it on a work stand first. If it shifts funky, start looking for a new rear derailer. If it shifts nice and smooth, save your money.

I agree to a point. If I already owned it, I'd give it a try to see for myself. My bet, however, is that it isn't going to work.

The issue isn't chain wrap, it's that the upper pulley rubs against the biggest rear cog. You can dial in the B-screw to pull the derailleur back, but you'll probably run out of travel. One possibility is to find a longer screw. Another is to remove your B-screw and install it from the other side so that the head rubs against the dropout. That'll give you a few more millimeters which may be enough.

Is there any major difference with an 8 speed 105 short cage? I've got a 28 on there now and no problems but am going up to Colorado at the end of the month for the BTC, and might like having a few more gears, I've got a compact crankset, but not enough money to upgrade to a tripple...I've been climbing some really big hills here, and have survived, but am concerned about back to back days with REALLY large climbs. What do you think cyc? i've seen you post on here a lot and you seem to know your stuff, should I try a 32?

Wondering what the largest cassette I can use with my Ultegra triple R.D. and triple crankset. I'm preparing to do some serious climbing and want more than a triple with a 12-26 cassette. Can I use up to a 32 tooth cassette without changing the rear der. since it's already a long cage?

Cage length does not correspond to largest cog. Largest cog capacity is determined by the RD's parallelogram design/length. That is the main difference between "mountain" and "road" RD's. Long cage/short cage corresponds to the difference of chainrings, e.g. how much chain the RD needs to absorb going from the largest chainring to the smallest (this is known as "takeup capacity"). It just so happens that most mountain bikes come in triple configuration, and that's where cage length comes into play.

Anyway, as for your specific case: I would try the 32T cassette. It might work. You'll need to adjust the B-tension screw on your RD so that the pulley wheels do not rub against the largest cog (which will cause premature wear on the pulley, chain, and cogs). If you can make that work, you're all set. I've heard of it happening; depends on your frame (dropout orientation/shape/etc.). There is a good article by Sheldon Brown on how to do this at http://sheldonbrown.com/derailer-adjustment.html#rear

If it doesn't work, you can pick up a mountain RD for relatively cheap (~$50 for Deore quality which is on par with 105 or so).

Biggest issue may be finding the cassette itself. If you have 10s, you are probably out of luck for finding a cassette with larger than a 28T (at least, not yet...we keep hearing that Shimano will have 10s "mountain" stuff out RSN). You could make your own with loose cogs and 10s spacers. 9s 34T cassettes are plentiful though.

Is there any major difference with an 8 speed 105 short cage? I've got a 28 on there now and no problems but am going up to Colorado at the end of the month for the BTC, and might like having a few more gears, I've got a compact crankset, but not enough money to upgrade to a tripple...I've been climbing some really big hills here, and have survived, but am concerned about back to back days with REALLY large climbs.

Same concepts apply. I had a similar situation on one of my bikes. I was unable to use a 105 RD on my 8s 32T so I ended up getting a "mountain" RD. But it works just fine with the 8s "road" shifters.

Is there any major difference with an 8 speed 105 short cage? I've got a 28 on there now and no problems but am going up to Colorado at the end of the month for the BTC, and might like having a few more gears, I've got a compact crankset, but not enough money to upgrade to a tripple...I've been climbing some really big hills here, and have survived, but am concerned about back to back days with REALLY large climbs. What do you think cyc? i've seen you post on here a lot and you seem to know your stuff, should I try a 32?

A 30 tooth is really, really pushing a short cage derailer. I don't think a 32 would work at all. You could probably pick up a Deore derailer (mountain bike) for fairly cheap (certainly less than a new crank) and then go with an 11-34. You'll probably need a new chain too. The mountain bike rear derailers work just fine with STI by the way. I have an XT with 105 shifters on my touring bike and it works like a dream.

As with most things bicycle, I'd say try the long cage with a 32 or 34 tooth cog first. You might be suprised. I've run 30 tooth cogs on a short cage Ultegra before without ill effect. I'd suspect that a long cage would be able to handle the chain wrap quite well. Put on the cassette and put it on a work stand first. If it shifts funky, start looking for a new rear derailer. If it shifts nice and smooth, save your money.

been there. done that. it doesn't work.

ed rader

Same concepts apply. I had a similar situation on one of my bikes. I was unable to use a 105 RD on my 8s 32T so I ended up getting a "mountain" RD. But it works just fine with the 8s "road" shifters.


yep -- short cage = 28 tooth cog. there may be exceptions but that's pretty much the rule.

ed rader

A 30 tooth is really, really pushing a short cage derailer. I don't think a 32 would work at all. You could probably pick up a Deore derailer (mountain bike) for fairly cheap (certainly less than a new crank) and then go with an 11-34. You'll probably need a new chain too. The mountain bike rear derailers work just fine with STI by the way. I have an XT with 105 shifters on my touring bike and it works like a dream.

the thing i'd recommend is checking sheldon brown's webpage. it explains why cage length isn't the determining factor and will tell you what will work and what won't.

of course there are exceptions....

ed rader

the thing i'd recommend is checking sheldon brown's webpage. it explains why cage length isn't the determining factor and will tell you what will work and what won't.

of course there are exceptions....

ed rader

From Sheldon Brown's Bicycle Glossary (http://www.sheldonbrown.com/gloss_ca-g.html)

Rear derailers are also commonly designed for a particular maximum size 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.

I'll also mention that many folks seem to be a bit mystified and intimidated by derailers. They're actually quite inexpensive and easy to replace, so it is foolish to allow the limitations of a particular derailer to keep you from having the gearing appropriate to your riding style/needs.

That's why (and I have done it) I suggested trying the cassette before investing in anything other than a new cassette and chain. If it works - gravy. If not - plan B. Always start cheap and work your way up;) Personally, I'd be very suprised if a Shimano long cage derailler wouldn't handle at least a 32 tooth cog.

Thanks for all the advice. I checked Sheldons' website and talked to a few experienced guys around here. I'll try a 32 tooth cassette and if it works, great! If not, I'll get a mtb derailer. I'll let you know what I find out to work.

yep -- short cage = 28 tooth cog. there may be exceptions but that's pretty much the rule.

No, the rule is, short parallelogram = smaller cogs. Again: cage length does not determine cog capacity. People get it mixed up because virtually all RDs that can handle larger cogs sold today just happen to be long cage, so they equate the two. But those FDs are long cage because they're normally paired up with triples on the front, NOT because of larger cogs. There are short cage (long parallelogram) RDs that can handle larger cogs. Or at least, there used to be...I miss sydney, if were here he'd give us all a good tongue lashing about this topic (again).

I had a MTB years ago with a touring derailluer and a 38 tooth cog, no problems. I used it to commute in the snow in Colorado. Later I had the cluster/derailluer put on a Miyata 1000 touring bike and went up Mt. Evans on the 14,200+ high road.