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Derailleur Cage 5-10 Degrees Out of Plumb - Do We Care?

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Derailleur Cage 5-10 Degrees Out of Plumb - Do We Care?

Old 08-29-22, 12:17 PM
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Harold74
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Derailleur Cage 5-10 Degrees Out of Plumb - Do We Care?

I'm a bit of a nut for perfect shifting. The perfectionist in me wants my derailleur cages to be perfectly parallel to my cogs at all times. That pretty much is the case on a 105 short cage setup that I built in the spring. However, it is not the case on:

1) My wife's bike shown in the picture below which is a medium cage Tiagra 4700 RD or;

2) The long cage Deore LX on my 1991 Miyata 1000 who's cage is the length of a baby's arm.

So my question is this. Is the degree of cage out of plumb-ness shown below a problem? Or is it just a consequence of the derailleur "settling in" to there being some degree of cross chaining in most gear combos? I suspect it's the latter.

Additional information on my wife's bike that might be relevant:

- She bought it from an elderly coworker with balance issues. The coworker dumped the bike a couple of times on the road and, by the look of the dropouts, maybe a few times on a trainer.

- My wife recently dumped the bike on the drive side while stationary. She wound up stomping right on the derailleur somehow.

- Prior to taking this photo, I installed a brand new derailleur hanger, chain, and cassette. With the Park Tool gauge on it, it's got about 1/4" gap up near the seat post. This would actually tend to tilt the derailleur the other way I think.

- The bike in the photo shifts quite well as is. Maybe a little noisy at the extremes.

- The tilt is at a maximum at the largest cog and tends to disappear towards the smaller cogs.

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Old 08-29-22, 01:28 PM
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This is going to degrade shifting and it's best to get the hanger aligned. Get the tool below. It is only $50 and is nearly identical to the more expensive Park Tool version. I own both and they work equally well. It is a handy tool to have because derailleur hangers getting hit is something that happens all the time. You'll be able to check your bike on a regular basis to keep it shifting well. It takes just a couple of minutes.

https://smile.amazon.com/dp/B077SZBZ...roduct_details
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Old 08-29-22, 01:58 PM
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Thanks for your response Yan. However, as I mentioned at the top:

1) I already have the park tool.

2) The hanger is fairly well aligned.

3) I'm quite confident that the tilt is being generated within the derailleur itself.
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Old 08-29-22, 02:57 PM
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Did you check fore-aft hanger alignment in addition to top-bottom? That can also cause the cage to appear slanted.
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Old 08-29-22, 03:37 PM
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Originally Posted by Yan View Post
Did you check fore-aft hanger alignment in addition to top-bottom? That can also cause the cage to appear slanted.
Yup, 1/8th points around the whole circle.

I'm pretty sure that it's not he hanger alignment. Rather, it's the derailleur itself.

What I'm mostly interested in is whether or not this level of cage tilt is something warranting a fix or just the way that a broken in derailleur is.
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Old 08-29-22, 03:57 PM
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If it shifts fine, enjoy a bit of extra clearance from the spokes.
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Old 08-29-22, 04:42 PM
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Originally Posted by Harold74 View Post
I'm a bit of a nut for perfect shifting. The perfectionist in me wants my derailleur cages to be perfectly parallel to my cogs at all times. That pretty much is the case on a 105 short cage setup that I built in the spring. However, it is not the case on:

1) My wife's bike shown in the picture below which is a medium cage Tiagra 4700 RD
If the above is true, just buy another RD-4700-GS and keep this one as a backup.

Compare both and see if you can “tweak” the old one closer.

John
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Old 08-31-22, 01:31 PM
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Sometimes, through manufacturing defect, a derailleur cage has a twist to it. As the chain moves down the cluster the angle of the cage changes, and so does the angle of the chain as it enters the cage. To test this,shift to a noisy gear and tweak the cage at the tension pulley with the left hand while cranking with the right to see if the noise diminishes. If that works, make the tweak permanent by taking an adjustable wrench to it. Shifting to a gear that puts the cage fully vertical helps you eyeball your tweak.
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Old 09-01-22, 08:00 AM
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I'd just grab the cage and try to straighten it manually, as John suggested. It's not that big a bend.
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Old 09-03-22, 01:22 PM
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This is a case where the only downside of the disease is the presenting symptoms. If it shifts well then you are not at risk of having that condition cause harm to the rest of the system. If you weren’t shifting well, or if the bend really bothers you, you could try to manually bend it straighter or swap the derailer.

When I get a scratch on the bumper of my car I leave it. My friend on the other hand sends it to the paint shop for repair. Both valid, just preference.
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