Rear derailleur hanger alignment

Discuss light weight issues concerning road bikes & parts.
Vagabond
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by Vagabond

Stupid question time. I'm new to wrenching but I've dove right in. Just finished building my first bike aside from the steerer tube cutting. Is it possible to damage a carbon frame while adjusting a hangar? In particular, where the dropout merges with the carbon? Thanks folks.
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bikerjulio
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by bikerjulio

As long as the rear wheel is clamped firmly in place, it's really the skewer end that's holding the hanger in place, and would also prevent too much stress on the dropout.

I'm going to look at my BMC again as I seem to recall the hanger being carbon too, and therefor not too keen on being realigned.
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Ozrider
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by Ozrider

It doesn't take much to bend many derailleur hangers as they are designed to bend/break if knocked in order to save the frame from damage. Some are just a bit too "soft" and tend to slowly bend over time with the forces of changing gears
Also derailleurs are fairly exposed and often take little knocks without us being aware of them, loading bikes, slight nudge during a race, laying bike down on derailleur side, etc, etc.
I have mine checked every few months.
A good LBS will check alignment when assembling a bike as it is easy to suffer a knock during transit and unpacking. Unfortunately many bike shops and bike "supermarkets" do minimal assembly out the box and their bikes are often poorly assembled and adjusted with cables too long, and adjustment barely acceptable.
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BRM
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by BRM

Vagabond wrote:Stupid question time. I'm new to wrenching but I've dove right in. Just finished building my first bike aside from the steerer tube cutting. Is it possible to damage a carbon frame while adjusting a hangar? In particular, where the dropout merges with the carbon? Thanks folks.


Yes thats possible.
Depends a bit of how well the construction is, in practice most of the time its not an issue.
With these kind of things you Always need to look out not to damage things.
Especially when the dropouts are carbon too you best should bend the derailleurhanger not on the bike self.

goodboyr
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by goodboyr

Take a look at the newer cannondale ones. The replaceable dropout "sandwiches" the frame connection. You can't bend these on the bike or you may break off the carbon tab inside the sandwich.

Bridgeman
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by Bridgeman

Rick wrote:Yes, typical.
Yes they go out over time due to random impacts you may not be aware of.

As above, make sure you are rotating the wheel to a consistent point as measuring alignment.

"Perfect" may be considered with a slight inward twist rather than perfectly straight with wheel by some. But you probably can't go wrong with straight.


Great observation. I've noticed while in gears towards the small end of my cassette, and because of the slight offset relative to the front chainrings, the chain is rubbing against the cage. A slight twist would provide the perfect bias to better overall alignment to prevent this contact.

This is actually a topic I've been wondering about. If pro mechanics and shops introduce a slight hanger bias to compensate for this offset. My hanger has the derailleur perfectly parallel to the wheel, yet you can clearly see wear from the chain on the cage while in the smallest 2 gears.

I'm in the market for a hanger tool as well, and will be trying this out to tweak it to a better balance.

em3
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by em3

All rear mech hangers should be aligned while on the frame and with skewer clamped ( including the Cannondale sandwich-type)...as long as your wheel is installed you will not damage dropouts/frame (unless of course you are ham fisted). There is no way to align your hanger off the bike and certainly not without the wheel installed. EM3
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Rick
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by Rick

I use a compact chainset and like to cross-chain mercilessly. So, for me, the slight inward bias allows me to get on the small-small without rubbing the big chainring.
It is not such a concern on bib-big, because everything clears easily. Although I can hear a bit of noise on the extremes due to the poor chain alignment as the chain rolls off the cogs.

goodboyr
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by goodboyr

em3 wrote:All rear mech hangers should be aligned while on the frame and with skewer clamped ( including the Cannondale sandwich-type)...as long as your wheel is installed you will not damage dropouts/frame (unless of course you are ham fisted). There is no way to align your hanger off the bike and certainly not without the wheel installed. EM3

Cannondale specifically tells you to not do that. And the the two himods I've built had perfectly aligned ones, so I didn't have to try.

bombertodd
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by bombertodd

How does Cannondale want us to align the derailleur?

I can't think of any other good way except on the bike. I've done a few Super Six's and Caad's the traditional way with great results.

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Guerdi
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by Guerdi

I have just seen that shimano makes a nice one (shimano tl-rd11).

Image

I use a more basic one (cyclus), but it does make the job as well.

5 8 5
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by 5 8 5

Guerdi, that is a nice one. Just checked the price .....ouch!

BTW, it's worth checking that the hanger bolt(s) is / are tight (preferably loctited) as that can give some weird and wonderful results when trying to align a hanger or setup gears.

I've had a couple of frames straight from the manufacturer where the hanger has been slightly loose out of the box.

mattr
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by mattr

TBH, as it's only an alignment tool, not really for measurement, a stiff enough bit of wood and a couple of bolts will do the trick. Spending $200 on a stick to bend your gear hanger is really a bit excessive, unless it's for a workshop where durability over hundreds or thousands of applications is needed.

For the home mechanic, the cheapest you can get will easily do the trick.

They even use precision sticks to align bits of cars and jet engines. As long as you only need them to either be parallel or at right angles............

em3
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by em3

goodboyr wrote:
em3 wrote:All rear mech hangers should be aligned while on the frame and with skewer clamped ( including the Cannondale sandwich-type)...as long as your wheel is installed you will not damage dropouts/frame (unless of course you are ham fisted). There is no way to align your hanger off the bike and certainly not without the wheel installed. EM3

Cannondale specifically tells you to not do that. And the the two himods I've built had perfectly aligned ones, so I didn't have to try.


I think the Cannondale sandwich hanger is actually one of the best designs, allowing for full contact on the dropout and good even clamping on the hanger on both internal and external faces. I too have read that Cannondale warns against using the alignment tool but it is a simple liability CYA warning, unlike the warning stickers placed on new bikes these days. I have used an alignment tool on the same design Cannondale hanger (assuming you are speaking about the design posted in URL below) and the DAG tool works just fine....no different then aligning any other hanger.

http://www.cannondaleexperts.com/Cannon ... p_271.html

EM3
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goodboyr
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by goodboyr

Em3: Yup...thats the one. Good to know its possible. The warning in the evo manual is quite dramatic, and gives no advice as to how to accomplish off the bike. In any case, as stated, i was lucky in the builds. Or they are made in alignment assuming the frame dropouts are well molded (which is extremely surprising considering we are talking about cannondales!). I assume at one point they will become misaligned as most do.......and then I will check by installing the spare I bought, and then in the last resort, pull out the DAG........

ps. Just ordered the Abbey tools HAG, my DAG is getting sloppy.

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