Correct chain length?
05-31-20, 03:23 PM
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Correct chain length?
I replaced the chain on my bike and sized it according to an chain sizing app. I'm wondering if my chain is tad short or just fine.
Big/Big
Small/Small
Big/Big
Small/Small
Last edited by ammarolli; 05-31-20 at 04:04 PM.
05-31-20, 03:38 PM
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1x or 2x? Assuming the two pics are big-big and small-small? I'd say that looks good.
05-31-20, 03:39 PM
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I'd go by the one of three procedures shown on page 8 or 9 of this manual. https://si.shimano.com/pdfs/dm/DM-RD0003-09-ENG.pdf
I'm betting you have a 2x front, so probably the second procedure for cassettes that have a large sprocket with 28 or more teeth.
Does look a little stretched out in the big big. So are you still within the specs with regards to max cog size and other stuff?
However I'm not saying it won't work if you exceed the specs. But you are in basically experimental territory and you have to make the determination if it works properly and won't eat itself. I've done it myself, it's just not an easy thing to say that you have done it right just by looking. What does it shift like when you ride?
I'm betting you have a 2x front, so probably the second procedure for cassettes that have a large sprocket with 28 or more teeth.
Does look a little stretched out in the big big. So are you still within the specs with regards to max cog size and other stuff?
However I'm not saying it won't work if you exceed the specs. But you are in basically experimental territory and you have to make the determination if it works properly and won't eat itself. I've done it myself, it's just not an easy thing to say that you have done it right just by looking. What does it shift like when you ride?
Last edited by Iride01; 05-31-20 at 03:45 PM.
05-31-20, 03:43 PM
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05-31-20, 03:47 PM
#5
Dangerous Old Man
Rule of thumb, make chain as long as possible in the small/small, you want just long enough the derailleur mechanism doesn't rub on itself...done..
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05-31-20, 03:53 PM
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More important Rule of thumb - make sure it's long enough in the big/big so you don't rip your derailleur apart and stuff it into your wheel.
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05-31-20, 04:26 PM
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How does it compare to your old chain (assuming you didn't make any changes in gearing)?
If no changes, is there a reason why you'd want or need a different chain length?
If no changes, is there a reason why you'd want or need a different chain length?
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05-31-20, 04:38 PM
#8
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in normal use you should never use the Big-Big or the small-small .. You should Know that..
have you figured out the gear ratio grid yet? to know when you change chainring/cog combinations in sequence?
...
have you figured out the gear ratio grid yet? to know when you change chainring/cog combinations in sequence?
...
Last edited by fietsbob; 05-31-20 at 04:42 PM.
05-31-20, 04:57 PM
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What is the gear ratio grid? I have 2x10 34/50 in the front and 11-34 in the back.
05-31-20, 05:01 PM
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It's the same length as the old one but I have a feeling that the chain is bit short if I accidental shift into Big/Big.
05-31-20, 05:11 PM
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Since you seem to have been able to shift into big-big (test this gently, while turning the crank by hand) you should be OK, but it is better to err on the long side, as a slack chain will not break anything.
05-31-20, 07:17 PM
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05-31-20, 07:23 PM
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It's pretty common for OEM chain lengths to be a link shorter then what I call ideal. Why? because both pulley knock is reduced and after about 110 bikes the factory gets a free chain
I am of the "make the chain as long as it can be and still work well" camp. Why? Because it's easier to shorten a chain then to lengthen it and sometimes that extra link gets used up in an "incident". Andy
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05-31-20, 10:26 PM
#14
Dangerous Old Man
If you have a problem with that, then you have a chain wrap problemo. The chain can not be any longer than the Small/Small or there would be problems...good, solid, basic rule.
05-31-20, 10:47 PM
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Do it exactly as described in RD manual. If chain is too long, shifting will be less crisp.
06-01-20, 08:18 AM
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I just added a 40t cog and tried out the old chain on the stand. It shifter into big-big, but it was close. When going to the new chain, I broke it a couple links longer. Shifted better and had more peace of mind.
When in doubt always break a chain longer first, then see how it works. It is easier to remove links than add.
For your situation, I would have gone a couple links longer.
John
06-01-20, 08:32 AM
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You are right to worry about it being too short. but if you have clearance between the pulley wheel on the cage and all the cogs on the cassette, then it probably is okay. B screw might help if not.
If you can, you might add back to make it the next longer. Then see if you have good shifting when you ride through out all the ranges. If your chain starts coming off, then possibly its an indication it need to be shorter. Though you need to check the DR limits too.
06-01-20, 02:05 PM
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06-01-20, 02:18 PM
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Small-small shouldn't happen too much, but big-big can happen with a sudden change in terrain for a short distance; especially around a blind curve. More so on a mountain bike.
When it happens, you can't really throw the chain in two directions at the same time, so you drop it into the large cog and power up.
John
When it happens, you can't really throw the chain in two directions at the same time, so you drop it into the large cog and power up.
John
