Changing from 12-25 to 12-27- chain length or RDer capacity?
I've changed the rear wheel on my tourer and put on a new 12-27 cassette (was 12-25). Front is 52-39-30. Ultegra 10 speed, long-cage rear derailleur, triple-specific front. Now it is _not_ a gear combination that I would be using anyway but I do find I have trouble changing into the 27 if I am in the 52 at the front; it just won't go up. If I am in 39 (or 30) I can change into the 27 fine, but if I shift up to 52 at the front it starts to get problematic and slips back down to 25.
Now nothing seems to be about to snap off or whatever in this situation so I am wondering if I really need to do anything. As I say I don't use the two extreme combos anyway.
Is this due to chain length or is it derailleur capacity? As far as I can tell my Ultegra long-cage rear derailleur has a capacity of 37t with a max 27t at the back and that is now what I have (52-30)+(27-12)=37. I have also seen suggestions you can go 2t beyond spec with Shimano derailleurs without problem.
My chain is maybe 3,000km in but doesn't seem to be worn (by the ruler test) - it has generally only been out in the dry and I keep very good care of it. There is no skipping whatsoever. So I don't necessarily feel I _have_ to change it.
Should I get a new chain anyway and leave an extra link in it compared to what's on at the moment? Or is it more likely to be a derailleur capacity issue?
I don't want to be in a situation where an accidental shift into 52-27 wrecks something either!
Now nothing seems to be about to snap off or whatever in this situation so I am wondering if I really need to do anything. As I say I don't use the two extreme combos anyway.
Is this due to chain length or is it derailleur capacity? As far as I can tell my Ultegra long-cage rear derailleur has a capacity of 37t with a max 27t at the back and that is now what I have (52-30)+(27-12)=37. I have also seen suggestions you can go 2t beyond spec with Shimano derailleurs without problem.
My chain is maybe 3,000km in but doesn't seem to be worn (by the ruler test) - it has generally only been out in the dry and I keep very good care of it. There is no skipping whatsoever. So I don't necessarily feel I _have_ to change it.
Should I get a new chain anyway and leave an extra link in it compared to what's on at the moment? Or is it more likely to be a derailleur capacity issue?
I don't want to be in a situation where an accidental shift into 52-27 wrecks something either!
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Comments
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did you lengthen the chain when changing the cassette?
It is probably a bit short if you haven't because you've added a couple of teeth.0 -
No, didn't lengthen the chain. I am presuming that I am looking at a new chain in that case, might do that anyway given the chain age even though it doesn't seem to be worn (after all it is easier to shorten a chain than lengthen it
Would anyone have an idea as to how many more links I should leave in the new chain (I generally use the hang old and new chains on the wall method to get the right length, have never tried the stick on bike/derailleur angle thing.)0 -
How does that hang on the wall thing work? Generally you thread the chain over the big-big combination, bypassing the derailleur, and add a link for chain length. New cassette usually means new chain as welll anyway.0
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The hanging on the wall thing is just a quick way of making sure the new chain is the same length as the old one, you just hang the old one on a nail and stick the new one beside it, pretty obvious then where you need to break it!
Obviously this will only give you the same length and I may need longer as I now have a 2t bigger sprocket on the back. Thanks for that tip on how to measure. I think I'll order a new chain.0
