[tom_h]

Recently added a Park DAG-2 derailleur hanger alignment guage to my tool collection.

Checked alignment on my carbon frame, '09 S-Works Tarmac ... mildly surprised to measure it beyond Park's recommended tolerance of +/- 4 mm (measured at wheel rim).
Mine was up to 10mm off :-O

The Campy 11 speed shifts fine, but now I'm thinking maybe it could be even better, and I didn't know what I've been missing.

My question: Is it safe to attempt bending the aluminum hanger back into correct alignment, while the hanger and wheel are clamped inside the carbon frame?

Last thing I need, is cracking the carbon fiber drop-outs!
Alternatively, trying to bend the hanger when it's removed from bike seems safer, but more hit-and-miss.

 

[frdfandc]

Its not an issue. You are only moving the derailleur hanger a few mm. and don't have to use a lot of force to do so either.

 

[Touch0Gray]

I did mine on my trek and the hanger is NOT removable, no problem...

 

[Pirx]

My question: Is it safe to attempt bending the aluminum hanger back into correct alignment, while the hanger and wheel are clamped inside the carbon frame?

Yes, that's perfectly safe, and the standard way to do it. Do not do it with the wheel removed. With the wheel in there, the load on the frame from the adjusting process is very small. Your frame "suffers" a lot more simply from you plopping your fat butt on its saddle...

Last thing I need, is cracking the carbon fiber drop-outs!
Alternatively, trying to bend the hanger when it's removed from bike seems safer, but more hit-and-miss.

You'd never get it right this way. Well, maybe you would be able to do it, but it would take a lot of tries.

 

[Mike Prince]

If it is shifting fine, I would leave it alone.

 

[tom_h]

I went ahead and re-aligned the RD hanger, following Park's instructions. Was a bit of an iterative procedure.

From previous 10mm max deviation, I reduced it to 2mm, or +/- 1mm, at all four quadrants of the wheel rim. Even the original 10mm corresponded to "only" about 1.8º out-of-parallelism, so these are very small amounts.

Qualitatively, the Campy RD now shifts noticeably faster (15% ??) both up and down, and shifts are a bit quieter, too!

As mentioned previously, I always thought my Campy bike shifted "fine" before, as least as well as my other (Shimano) bike. Apparently I didn't know what I was missing!

I am sold on this ... I would now check RD alignment before doing any significant tuneup or adjustment.

BTW, not too clear in Park's instructions, but make the adjustment at the 180º opposite point on the wheel rim, about 1/2 of the gap measured on the guage. Reducing the gap at point B, simultaneously increases the gap at opposite point A by the same amount. This will result in net zero differences in the gap.
Better to ease into good alignment, rather than have to "undo" the bend on the hanger and risk weakening it.