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Change crankset, lengthen chain?

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Change crankset, lengthen chain?

Old 04-23-19, 02:38 PM
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rbrides
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Change crankset, lengthen chain?

I'm considering replacing my 48/32 with a 52/36. Should I lengthen the chain? Or, could I expect the derailleur to work properly with these slightly larger diameter chain rings? Is there a formula or calculation for determining correct chain length?
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Old 04-23-19, 02:43 PM
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Bill Kapaun
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IF the chain was properly sized, you'd need to ad 1" or 1 link set.
Your chain might be sized a bit long?
Put the chain in BIG:BIG.
Measure as in the pic.
You'd need 4 half links minimum "slack" to use the same chain.
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Old 04-23-19, 03:04 PM
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Yep. Usually I set the chain length so that in the small/small combination the addition of 1 link (or half a link, depending on if you are using pins or master-links) would cause the chain to drag against itself as it feeds past jockey wheel through the derailleur machanism. This allows the longest possible chain & the most buffer against being too short in the big/big combination. On occasion that means a b-screw adjustment to add a bit of tension to the system.

I then go to the second biggest cog and screw in the b-screw until the upper jockey wheel has plenty of clearance to guide the chain to the biggest cog with out hitting it. Hesitation in the shifter indicates you don't have enough clearance.

Check you're derailleur capacity on the spec sheet. So long as you don't exceed that magic number, you're fine.

I suspect you might need to add a full link. But you might get lucky, depending on where you are starting from.
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Old 04-23-19, 03:23 PM
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How old is your current chain? Cassette? Years, Miles, Unknown, or Measured Stretch?

I'd be tempted to start a new crankset with a new chain.
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Old 04-23-19, 07:50 PM
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You'll likely need a longer chain. Unless the current chain is quite fresh, you'll probably want a whole new chain, and that would also likely need a new cluster on the rear wheel to prevent wear mismatch between the new chain and worn cluster.
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Old 05-02-19, 08:52 AM
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rbrides
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2018 Specialized Diverge Comp I bought new in September. About 1800 miles.
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Old 05-02-19, 08:55 AM
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Thanks all for the replies and input.
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Old 05-02-19, 09:13 AM
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Buying a new chain is probably a timely thing to do, due to wear
(consider a new cassette as well for same reason)

and now modern chains should not be lengthened , like done back in the 70's,

but use 2 quick links on either ends of an additional chain portion ..

so when you size a new chain , save any leftover portion , and pick up another couple quick links ,

for potential on the road broken chain repairs..







...
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Old 05-06-19, 08:25 AM
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rbrides
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Originally Posted by fietsbob View Post
Buying a new chain is probably a timely thing to do, due to wear
(consider a new cassette as well for same reason)

and now modern chains should not be lengthened , like done back in the 70's,

but use 2 quick links on either ends of an additional chain portion ..

so when you size a new chain , save any leftover portion , and pick up another couple quick links ,

for potential on the road broken chain repairs..







...
Good Advice, thanks!
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