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Old 05-18-06, 10:56 PM   #1
duongrn
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Am I doing something wrong? Cassette and Derailleur

So I slapped a 11-34 XTR cassette with my shimano long cage rear ultegra derailleur and ultegra shifters,
I've been reading the forums and they say that is not possible.

I've ridden it about 50 miles around in the lowest 34 gears and don't seem to have problems. My question is am I damaging the components? Why are people saying this isn't possible?

Thanks in advance,
Rick
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Old 05-19-06, 12:08 AM   #2
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Why wouldn't it be possible? It should be fine with the proper adjustments, which seem to have been made. If you don't seem to have problems, then you're correct - it's just fine.
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Old 05-19-06, 04:05 AM   #3
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Quote:
Originally Posted by duongrn
So I slapped a 11-34 XTR cassette with my shimano long cage rear ultegra derailleur and ultegra shifters,
I've been reading the forums and they say that is not possible.

I've ridden it about 50 miles around in the lowest 34 gears and don't seem to have problems. My question is am I damaging the components? Why are people saying this isn't possible?
The issue is the upper derailleur pulley rubbing the larger cassette cogs. If your's doesn't do that I wouldn't worry about it.
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Old 05-19-06, 07:09 AM   #4
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Originally Posted by the beef
Why wouldn't it be possible? It should be fine with the proper adjustments, which seem to have been made. If you don't seem to have problems, then you're correct - it's just fine.
Uh, because the Ultegra rear derailler is rated as being able to handle a max cog size of 27t. That's why he's asking - he's surprised that it works.
And I'm surprised that it works, too. That said, if the derailler cage and/or pully wheels aren't rubbing against the cassette, then I think you're good and in business. If this problem does occur, then you could just slap a LX or XT rear derailler on there and be in good shape.

I'd be interested to see some pictures, if you get the chance to post any. Pictures with the chain in the 34t cog, taken from an angle where I can see the rear derailler's top pully wheel.
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Old 05-19-06, 08:59 PM   #5
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crank/derailleur issue.

not to mention the stress on your chain from forcing too much wrap on that poor ultegra derailleur.
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Old 05-19-06, 09:24 PM   #6
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Quit worrying about what other people think or say. If it works for you, then that's all that matters.
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Old 05-20-06, 07:35 PM   #7
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Here are the pictures. Please let me konw if I am going to damage my parts by doing this. Thanks a bunch.
Attached Images
File Type: jpg two.JPG (89.8 KB, 68 views)
File Type: jpg three.JPG (90.4 KB, 73 views)
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Old 05-21-06, 06:28 PM   #8
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You barely have it fit in there, but it seems to be working.

There is more than one issue in determining how big a cog a derailer can take. Chain wrap is the obvious one - but sometimes over rated. That is, you really shouldn't be using the small cog/small chain ring combo, nor the big cog/big chain ring. Thus the effective range of chain that needs to be accounted for is reduced.

The second, and often overlooked issue is one that the derailer mfg can't account for - and thus needs to be conservative. What is the distance fromt he center of the derailer fixing hole to the center of the cassette. This isn't a given, although Shimano probably gives recommended specs. The farther the derailer is mounted from the cassette, the more room is available for a larger cog. You apparently have a longer distance from cassette center to mounting center than average.

BTW, the chain won't get stressed about you forcing too much wrap on the poor derailer. However, if you forget to call your mother every Sunday - well lets just say that an angry chain is an ugly thing.
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Old 05-21-06, 08:01 PM   #9
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I find that I have to shift my front gear more often now because I get more rub on my front derailleur.
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Old 05-22-06, 04:09 AM   #10
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Quote:
Originally Posted by duongrn
Here are the pictures. Please let me konw if I am going to damage my parts by doing this. Thanks a bunch.
Don't you feel a vibration through the cranks when you're using the larger cassette cogs? That wouldn't be satisfactory for me.
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Old 05-22-06, 01:18 PM   #11
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I don't get any vibration however, I do feel when I am the largest 34 I get this "click" about every revolution. It is like there is either too much or not enough chain.
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Old 05-23-06, 09:08 AM   #12
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Looking at your second picture, it appears that the chain is on the second-to-largest cog? In the first picture, it looks like the chain is on the 34, but in the second picture, the chain is pretty clearly not on the 34, it's on the next smaller cog. This is a concern because it seems like your top pulley is already dangerously close to the cog teeth, and so when it IS on the largest cog, your top pulley may be in contact with the cog teeth. That may be what the "click" is, or not, but you should definitely take a close look at the upper pulley wheel and the cage which holds the pulley wheel, to make sure that there is no contact with the cog when in the 34-tooth cog.

Last edited by simplify; 05-23-06 at 09:17 AM.
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Old 05-23-06, 01:54 PM   #13
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You are right, one of the picts is when it is the 2nd largest cog and the other one is on the largest cog.

Dumb question: why shouldn't the there be contact on the cog?
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Old 05-23-06, 02:15 PM   #14
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Quote:
Originally Posted by duongrn
You are right, one of the picts is when it is the 2nd largest cog and the other one is on the largest cog.

Dumb question: why shouldn't the there be contact on the cog?
Having the derailleur too close to the cog reduces the amount of "free" chain that floats between the cog and the pulley. This reduces the amount you can flex teh chain laterally to make a shift occur. With the pulley directly on the cog, it may not be possible for the spring-tension to pull the chain off the cog down into the next smaller cog.

Having too large of a gap is also a problem, because then the derailleur has to move a large amount to bend the chain sufficiently to move it onto the next cog. That's why the slant-parallelogram design was such a major breakthrough by SunTour. It moves the derailleur pulley at an angle to roughly match the angle of the tips of the cogs to maintain even spacing.

In this case, I think if it's working and shifting without getting stuck, he'll be OK. Like Cactus said, the drop of the derailleur-hanger may be a little more than average, so it's fine. Also the tension-spring on the pivot bolt can usually be adjusted to rotate the derailleur downwards more, giving more clearance. In this case, it looks like the adjustment-screw is fully-tightened as it is.
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