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Rear derailleur too stretched out?

Old 05-30-21, 11:41 AM
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pennpaul
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Rear derailleur too stretched out?

I'm swapping in a bigger 9-speed rear cassette on my road bike going from 11-28 to 11-36. I have a 53/39 in the front. I currently have a short cage Ultegra RD and also bought a longer cage Sora RD and new chain.

However, the new cassette came with a cheapo road link which I decided to give a try. It seems to work without having to change the RD or lengthen the chain. Now I'm thinking is it even necessary to swap RDs or am I risking disaster? The Ultegra RD should not work according to its specs, but it does.

I'm not going to try big-big, but big and half-way on the cassette is still OK.


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Old 05-30-21, 11:56 AM
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You are courting disaster. You had better ensure that the chain is long enough to shift comfortably into big-big or you will have a very unpleasant surprise when (not if) you forget and shift into that combination. You will be fortunate if you only tear up (or off) the derailleur and do not damage your frame.
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Old 05-30-21, 12:09 PM
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I am currently doing the same sort of change with my road bike.

Even with the hanger extender - which will let the RD shift up on to the 36T cog - the short cage derailleur arm is too short to tension a longer chain in the small-small combo.
So I think you should do everything you can to make even 'accidental' combinations like the big-big work.
Try the Sora.
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Old 05-30-21, 12:30 PM
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Originally Posted by pennpaul View Post
I'm swapping in a bigger 9-speed rear cassette on my road bike going from 11-28 to 11-36. I have a 53/39 in the front. I currently have a short cage Ultegra RD and also bought a longer cage Sora RD and new chain.

However, the new cassette came with a cheapo road link which I decided to give a try. It seems to work without having to change the RD or lengthen the chain. Now I'm thinking is it even necessary to swap RDs or am I risking disaster? The Ultegra RD should not work according to its specs, but it does.

I'm not going to try big-big, but big and half-way on the cassette is still OK.


all the road link (Iím assuming an extended hanger) does is give you clearance for the larger sprockets - it does not address the chain wrap issue, and your short cage RD isnít up to the task. You need a longer cage RD.
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Old 05-30-21, 12:35 PM
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Some rear DR's are less expensive new than the wolf tooth extender some buy to try and make the old DR work.

Hangar extenders only allow you to get clearance from the cassette. Not increase the capacity so you can have huge differences from the small/small to the big/big combos.

What you need to look for is how close does that jockey wheel get to any of the cogs as you go from the smalls to the bigs. In the other direction, you don't want any slack in the chain as you go to the smalls.
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Old 05-30-21, 12:57 PM
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Originally Posted by Iride01 View Post
Some rear DR's are less expensive new than the wolf tooth extender some buy to try and make the old DR work.
True.
But the knockoff extenders are under $5 with shipping, so OK for experiments, for me.
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Old 05-30-21, 02:07 PM
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Here a a couple of pics of my bike setup.
Triple chainrings 52-42-30 and 12-36 cassette.
I had to swap out the Ultegra RD for a Deore XT with a hanger extender.

Big-big 52-36


Small-small 30-12 Almost touching, but isn't. Not a disaster, but I'd never deliberately shift to that combo anyway, as with the Big-big - it would only be for a few seconds until I realized I'd made a mistake.

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Old 05-30-21, 03:13 PM
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Exactly what everyone above posted. And why on earth do you post upside down photos? Just take them right-side up.
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Old 05-30-21, 03:25 PM
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You want your chain long enough to go big-big. Because someday you're going to forget what gear you're in and you're going to slam it into big-big. Small-small is a no-go for most of us, but at least if you find yourself there it will only be annoyingly noisy.
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Old 05-30-21, 03:27 PM
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VicBC_Biker gave some good pics that sort of show what I was trying to say. See how the DR is stretched out in the big's, but has clearance to the jockey wheel. My 105 5800 GS (mid cage) DR looks stretched out like that too when in the 52F/32R. While a lot of literature might make you think that is too stretched out, as long as you have the clearance to the jockey wheel and the DR isn't at it's limit to stretch out more, then you probably are okay.

And clearly when in the smalls the chain isn't hanging slack with a big curve in it.

As for your bike, you ought to have it right side up when you adjust shifting and DR's. Gravity does have some effect on the components that will be different when you turn it over. You can just hang your top tube over the corner of a table or clamp some 2x4's through a ladder to hang the top tube on. Sometimes I just hang the nose of the saddle on something.
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Old 05-30-21, 03:28 PM
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Originally Posted by dsbrantjr View Post
You are courting disaster.
Originally Posted by VicBC_Biker View Post
... the short cage derailleur arm is too short to tension a longer chain in the small-small combo...Try the Sora.
Well, I had nothing else going on this afternoon so I tried the Sora and I did need the new chain. Big-big just barely and small-small has enough tension. Now I've got to tweak the shifting. But man, that Sora derailleur is ugly.

Thanks for setting me on the right path,
Paul

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Old 05-30-21, 03:29 PM
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Originally Posted by cxwrench View Post
And why on earth do you post upside down photos? Just take them right-side up.
The photos are rightside up; the bike is upside down.
Without a bike work stand or a way to hang up the bike, it's easier to do derailleur adjustments with the bike upside down...but I haven't done that since the 1970s that because of all the 'stuff' that's attached to the handlebars on my bikes.
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Old 05-30-21, 03:31 PM
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Originally Posted by Iride01 View Post
As for your bike, you ought to have it right side up when you adjust shifting and DR's. Gravity does have some effect on the components that will be different when you turn it over. You can just hang your top tube over the corner of a table or clamp some 2x4's through a ladder to hang the top tube on. Sometimes I just hang the nose of the saddle on something.
Good points and good ideas.
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Old 05-30-21, 03:33 PM
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Originally Posted by pennpaul View Post
Well, I had nothing else going on this afternoon so I tried the Sora and I did need the new chain. Big-big just barely and small-small has enough tension. Now I've got to tweak the shifting. But man, that Sora derailleur is ugly.
And you didn't need the hanger extender, so that's a plus.
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Old 05-30-21, 03:35 PM
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Originally Posted by pennpaul View Post
But man, that Sora derailleur is ugly.
You won't mind so much when you are climbing walls and trees with your new low gears.
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Old 05-30-21, 03:45 PM
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pennpaul
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Originally Posted by VicBC_Biker View Post
The photos are rightside up; the bike is upside down. .
Yep, sadly no bike stand so this will have to do. Everything is easier to reach when the bike is upside down, but as someone else mentioned, gravity does play into it, too.

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Old 05-30-21, 03:47 PM
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Got a new cassette... Why not a new long cage derailuer and a new chain. It would appear this good looking bike deserves it...
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Old 05-30-21, 04:58 PM
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Originally Posted by zandoval View Post
Got a new cassette... Why not a new long cage derailuer and a new chain. It would appear this good looking bike deserves it...
That's what he did...
New Sora
New chain
New cassette + hanger extender.

But, I feel the OP's pain...I hated to take that purty Ultegra RD off the bike.
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