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PostPosted: Fri Dec 06, 2013 9:49 pm 
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Hello!

First, yes, there was an old thread about this (here) but since that thread was circa 2009 and included a banned member (DocRay, remember him anyone?) I thought that a new thread might be o.k.

A recent frame that I've ordered has arrived and it came with one derailleur hanger, as per usual, but I wanted to look into getting extras to have on hand - and if possible, lose some weight in the process. I don't see there being a significant weight gain or loss in going from forged to CNC (or vice versa), so forget the weight issue... but stiffness?

1. Are CNC'd derailleur hangers stiffer than the same shape in forged? (Both are aluminum)
2. I noticed that, for the most part**, buying a forged derailleur hanger will cost about the same as a CNC hanger. So what's the benefit besides machinery awesomeness?
3. Does anyone have experiences with their CNC derailleur hangers that they would be able to share, positive or negative?

Currently I'm seeing forged hangers from the common sources (Wheels MFG, Derailleurhanger.com, etc:.) but I've found a few places that are selling CNC ones... is there a difference? Is one better than another?
Pilo, NorthShore Billet, and 925 Engineering who somehow is offering the hanger at more than half the price of the others! ( :?: )

Thoughts?

Also: has anyone successfully tuned their modern derailleur hangers (non-integrated) to reduce weight? This thing in my hand is a frustrating 18g w/bolts. Too much.

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Posted: Fri Dec 06, 2013 9:49 pm 


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PostPosted: Fri Dec 06, 2013 10:15 pm 
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From a metallurgical view, forged is typically a little stronger than CNC, because the metal grain is aligned in the part. But I don't think there is a consitently measurable difference in stiffness or weight ....assuming the same alloy and heat-treat condition.

I think all the theoretical metallurgy would be swamped out by other factors, such as the accuracy of fit, or minor tolerance differences in thickness, hole sizes, etc.

Forged parts might be slightly heavier only because the are sometimes actually slightly bigger too, to account for the lessened ability to hold tighter tolerances in the forging process.

I, personally, wouldn't tune a derailleur hanger just to save a few grams, because material removal always lowers strength and stiffness.


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PostPosted: Fri Dec 06, 2013 10:33 pm 
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I think this sentence, from Wheels Mfg says all you need to know: "Wheels Mfg. derailleur hangers are precision-machined from high-grade 6061 aluminum for accurate shifting. Most stock hangers are forged from soft, low grade aluminum."

A CNC piece will usually be cut from high grade solid billet while a stamped or forged hanger will usually be forged from a cheaper/softer alum. IME the Wheels Mgf hanger are slightly thicker, resulting in stiffer hangers, compared to stock stamped junk that is often OEM on most bikes. The increased stiffness results in noticeably more positive shifting. As far as tuning a rear hanger?...other then chaining out bolts to TI which might but you a gm savings, I wouldn't mess with the hanger itself.

EM3

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PostPosted: Fri Dec 06, 2013 11:12 pm 
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I'm sure you have already switched to aluminum bolts?

Cannondale used to have a series of machined hanger's like this one:

Image

Don't know how much weight that hole saved but I worked on a lot of bikes with them (including many that switched from a solid one to this one) and there was no lack of stiffness noticeable when shifting - unlike going from the crappy forged ones to machined ones - immediate difference.

If I had some spares I would try some tuning.


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PostPosted: Fri Dec 06, 2013 11:56 pm 
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Stronger is better so long as it is weaker than the stays it is attached to.
The hanger is the part you want to break - first.


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PostPosted: Sat Dec 07, 2013 12:10 am 
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Afaits, excellent reference, thank you.

I think I'll pick up a few of the CNC ones and do a wee bit of tuning to reduce the weight on it. I don't think it will affect stiffness with what I have in mind (I may not be an engineer but I do have some idea of structural forces having studied architecture for my master's degree).

Re: bolts
Aluminum? Is that safe? I was thinking titanium might be a good way to go, but will aluminum hold?
The derailleur time is 'single hole' meaning the mounting portion uses a chainring-type bolt, similar to this:

Image

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PostPosted: Sat Dec 07, 2013 12:40 am 
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I'm not sure if you've seen this guys hangers. I bought two for my wife's Pinarello and they seem great (cheaper than Wheels MFG).

http://www.ebay.com/usr/925engineering


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PostPosted: Sat Dec 07, 2013 12:59 am 
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prendrefeu wrote:

Re: bolts
Aluminum


Don't forget, the clamp force of your skewer is present, and while I don't have any data to back it up I would imagine once your wheel is in that's more than enough. I have had no problems on my bike with an aluminum bolt (came stock).

Actually, remembering back to my shop days, I have seen a couple bikes that had lost the bolt and the rider had no idea - it functioned totally fine until you took the wheel out...


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PostPosted: Sat Dec 07, 2013 1:01 am 
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@bombertodd

Yes, see the original post. I linked to them already. So you've used them! Any thoughts on quality/stiffness? Issues?

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PostPosted: Sat Dec 07, 2013 6:05 am 
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prendrefeu wrote:
@bombertodd

Yes, see the original post. I linked to them already. So you've used them! Any thoughts on quality/stiffness? Issues?


My bad, I must have read right by that... :oops:


I'm not sure how my wife manages to bend her derailleurs so often, but the 925 one seems stronger than the Wheels MFG one when bending them back with my Park derailleur hanger alignment tool. I've noticed that a little too much pressure on the tool with the Wheels MFG hanger seems to bend and crack. I haven't had this happen with the 925 one, but I have only bent it back once.

From the CNC vs Forging, I would say that it doesn't matter. Shear strength is stronger with a forging but derailleurs aren't really sheared off (very unlikely), they are usually bent which would be a test of elasticity. The modulus of elasticity is the same in forgings and CNC for 6061 (most hangers). The bigger deal is what the hanger is made out of. If you get one made out of 7075 it would be stronger, and most likely a higher price too.


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PostPosted: Sat Dec 07, 2013 6:25 am 
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Thanks! The comparison between Wheels & 925 is interesting.

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PostPosted: Sat Dec 07, 2013 10:23 pm 
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We bought a replacement hanger from Pilo after a shop stripped out the stock hanger and we found getting an OEM replacement to be major hassle

In fact, Pilo was the only company making hangers for that particular bike model - and still is, I just checked all those other places.

The Pilo was beautifully a machined black hanger... visually it kicked the look of the bike up a notch if nothing else.
I have to assume it slightly improved shifting, but it was my wife's bike so I can't speak to it personally
The OEM one felt like crap in comparison once we pulled it off.

Anyway, "I'd do it again" :)

Try Pilo
(esp. if you aren't having luck anywhere else!)


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Posted: Sat Dec 07, 2013 10:23 pm 


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