Shimano Rear Derailluer

[NYCSlim]

Hi guys,

I'm using an Ultegra 52-36 mid crank set and recently switched to an 11-30 cassette. I can't be in the 36 in the front and go to the 30 in the rear or 52 in the front and 30 in the rear (not that I would want to do that but don't want an issue if I make a mistake). I couldn't figure it out for the life of me. My local bike shop said that I need to get a longer rear derailleur and a longer chain but the shimano site states that it can handle 11-30. Any help or advice would be appreciated.

Thank you in advance!

[cribbit]

What's stopping it from shifting?

[GregL]

Was your chain sized for a smaller cassette? If the chain is too short for the new cassette, shifting performance may be compromised.

Greg

[NYCSlim]

Cribbit - I'm not sure. That's what I'm trying to figure out.

Greg - I was wondering if that could be a factor but wasn't sure. I'll get a longer one and see if it fixes the issue. Thanks

[hokoman]

I think the b tension screw needs to be screwed in so the top pulley clears the 30 cog.

[GregL]

I think the b tension screw needs to be screwed in so the top pulley clears the 30 cog.
Great suggestion! Certainly "low hanging fruit" in this case.

Greg

[TheseGoTo11]

i think the b tension screw needs to be screwed in so the top pulley clears the 30 cog.

+1

[oldpotatoe]

Hi guys,

I'm using an Ultegra 52-36 mid crank set and recently switched to an 11-30 cassette. I can't be in the 36 in the front and go to the 30 in the rear or 52 in the front and 30 in the rear (not that I would want to do that but don't want an issue if I make a mistake). I couldn't figure it out for the life of me. My local bike shop said that I need to get a longer rear derailleur and a longer chain but the shimano site states that it can handle 11-30. Any help or advice would be appreciated.

Thank you in advance!

My advice is find a new bike shop..you don't need a new rear der, you probably need a longer chain and a well adjusted rear der..using mentioned B limit screw..your rig should work just fine with your crankset/rear der/cogset..

[Mark McM]

My advice is find a new bike shop..you don't need a new rear der, you probably need a longer chain and a well adjusted rear der..using mentioned B limit screw..your rig should work just fine with your crankset/rear der/cogset..

Based on the OP's minimal description, chain length and B tension screw adjustment would be my guesses as well.

It would be helpful if the OP could post a couple of photos of the drivetrain in the state where it can no longer shift to larger sprocket or chainring.

[dddd]

OP says that it won't even shift to the 30t when it's in the small ring, so this doesn't seem to be principally a problem of too-short chain.

If the bike had been properly set up with a 28t cassette, the 30t cassette would be affecting the chain tensioning by one mere link, no way would that prevent the chain moving to the 30t using either chainring.

And hard to imagine that a 2t increase in cassette size would outright prevent the chain from moving to the largest cog whether or not any B-tension adjustment was made.

I'm wondering if the cable is perhaps tensioned one full gear position too slack?

The possibility of the cable being one gear position too slack can be conformed by the presence of a "ghost" click at the small end of the cassette, where shifting one click in either direction causes nothing to happen, no derailer movement at all.

Seen this many times.

Also remembering that on Shimano's recent 11s shift levers, that there is a lever travel limit stop built into both levers as the cable has been pulled as far as the shifter is supposed to pull it.
In fact, the hi limit screw has been deleted from the front derailers, replaced by a hi-boost screw that essentially works opposite to a traditional hi-limit screw. Not much has been made of this, so I very much doubt that all of today's shop mechanics know how to properly adjust them without actually following Shimano's instructions.

[Mark McM]

OP says that it won't even shift to the 30t when it's in the small ring, so this doesn't seem to be principally a problem of too-short chain.

If the bike had been properly set up with a 28t cassette, the 30t cassette would be affecting the chain tensioning by one mere link, no way would that prevent the chain moving to the 30t using either chainring.

And hard to imagine that a 2t increase in cassette size would outright prevent the chain from moving to the largest cog whether or not any B-tension adjustment was made.

I'm wondering if the cable is perhaps tensioned one full gear position too slack?

Yes, the indexing off by one position is also a possibility. Or the inner limit screw might be set too tight. But you'd think a decent bike shop would have discovered either of these problems. In any case, a better description from the OP would be useful, to get a better feel of what the shifting dynamics are.

I friend once asked if I could diagnose a front shifting problem over the phone. She kept describing the problem as "It's too hard to move the derailleur to big chainring" and "it takes too much force to shift to the big chainring." So, I went through the usual checks that this description suggested - the derailluer limit screws, cable friction, even derailleur height (if the derailleur is too low, the cage can hit the teeth on the big chainring as it moves outward). None of that was the problem. After a bunch more suggestions and tests, it turns out the cable adjuster was set too tight - the shifter had hit the outer index position before the derailleur moved far enough to shift the chain. But since my friend thought it was a derailleur problem, she kept describing it as the "derailleur takes too much force to move", rather than the "the shifter takes too much force to move".

[NYCSlim]

Thank you all for the sound advice. Seems like my best bet is to find another bike shop first and see what they say in regards to the chain length and B tension screw.

[dddd]

You shouldn't have to say much, a competent bike mechanic should be able to diagnose this in under two minutes.

Editing here:
The question in my mind was who performed the cassette replacement, and whether they attempted adjustments to the derailer without knowing (or paying attention to) what they were doing(???).
Might have hastily mistaken the lo-limit screw for the B-tension screw and screwed it in a good bit. Easy to do when working on an unfamiliar derailer with socket-head screws having taken the place of the former Phillips-head screws.

[tombtfslpk]

Good advice from all.
If it was me, before I take it to another bike shop, I would flip the chain off the crankset (assuming it doesn't have a quick link). Hold the derailleur lower jockey wheel back and see if it shifts far enough over to align with the largest cassette cog.
If that works, I would expect the chain to be the issue. Lots of info here on how to determine correct chain length.
Good Luck, and welcome to the forum!

[NYCSlim]

Hi folks,
I took it to another shop and they had it fixed in 15 minutes. I guess that's my new shop now. Thank you again for the help and guidance.