Derailleur Hangers - Do they spontaneously break?

[ontarget]

I've never heard of a derailleur hanger spontaneously breaking while riding along, but I was recently told by a mechanic at one of the LBSs that it could happen. Hence, he likes to avoid adjusting/aligning them out of fear that, if they don't break during alignment, they may break on the road, leaving the customer stranded.

Any truth to this? I can see one breaking during alignment, but if it survives that I have a tough time believing it'll break on the road unless, of course, the derailleur gets hit or bumped by something.

[Cicli]

I know some guys that dont like to realign aluminum hangers once they have been bent for fear they will break. Aluminum doesn't like to bend and fatigues quickly from bending back and forth. I would not bend back a hanger that was damaged or bent in an accident but have no problem fine tuning a new hanger install.

[Black Dog]

If it is badly bent then replace, if not just re-align. Al is not that sensitive.

[seanile]

myself and two friends have broken alu hangers JRA. one was on a hillclimb though, so i don't know if the extra torque involved was the culprit. none had been bent back into place at any point previously.

[Cicli]

myself and two friends have broken alu hangers JRA. one was on a hillclimb though, so i don't know if the extra torque involved was the culprit. none had been bent back into place at any point previously.

Yeah, there is no real torque on a rear derailleur hanger while riding. Maybe during a shift but not while riding. Regardless of the hill or power output.

[Joel]

Yes! So the shop said...

Years ago I had dropped off my '84 Cannondale for a new headset at the LBS. When I went to pick it up, it had a new hanger bolted on. LBS said the existing hanger just broke when they picked up the bike :eek:.

I suspect the reality is that they dropped it...

That said, still have said bike, with said replacement hanger and pat '84 campy hanging on it.

You just can't make this stuff up!

[BobbyJones]

Yes, they do.

I wouldn't believe a JRA story if it didn't happen to a close friend.

I thought he was BSing me and I was waiting for the punchline.

I'd imagine absent of something noticeable like a stick, something has to hang up the works for it to happen, right? I'm wondering if something like a small pebble in a pulley, etc

[benb]

They absolutely weaken when they're aligned. You're bending them enough that they take a new shape. (Some Mech E. can tell us the correct term for this.)

Big difference from frame flex.. you never flex a frame enough that it permanently changes shape.

I broke one last month.. it got a stick in it... BUT it had been realigned a week or so before it broke.. it does make me wonder if it made it break easier. It snapped so incredibly easily.

[carpediemracing]

Metal doesn't spontaneously break. If it breaks it's because there's a stress raiser somewhere in there. It could be a manufacturing defect, so I suppose it's possible that the hanger just breaks, like maybe a brand new one that was never installed and it breaks immediately after installation. Never heard of that though.

The reality is that hangers bend a bit even on my bike. I swear I don't drop the bike drive side down, I don't abuse my bike, I just ride it. But after a few years the hanger is inevitably a bit bent in. I have no idea why. I'll tweak the hanger and it's good again.

Inevitably the hanger should break, although it doesn't happen much to me.

Still, though, I travel with a spare hanger.

[rnhood]

Yes, having and/or traveling with a spare hanger is good sense. Its an inexpensive part that can ruin your day if it breaks for whatever reason (there are several).

[dustyrider]

I've never heard of a derailleur hanger spontaneously breaking while riding along, but I was recently told by a mechanic at one of the LBSs that it could happen. Hence, he likes to avoid adjusting/aligning them out of fear that, if they don't break during alignment, they may break on the road, leaving the customer stranded.

Any truth to this? I can see one breaking during alignment, but if it survives that I have a tough time believing it'll break on the road unless, of course, the derailleur gets hit or bumped by something.

So the lbs doesn't own a derailleur hanger alignment tool, then? Seems odd. Maybe he wanted you to buy a new one...but how would he adjust it??
On a personal note: I just realized all 5 of my bikes don't have replaceable hangers. Win!

[benb]

It's funny how bikes that don't have replaceable hangers tend to never have any trouble with them...

Never had any issues with my Ti Serotta that just had a beefy Ti hanger built into the dropout. No issues with my All City Space Horse that is pretty much the same thing just steel.

I have had trouble with both of the carbon bikes I've had. I don't really recall ever having any issues with Aluminum bikes (which I've put a ton of miles on) even though those have all had the replaceable hangers. My MTB gets the most sticks in the chain for sure and it's close to 12 years old now and has never had any issues.

[ontarget]

Thanks for all the responses, folks. A lot of useful information was provided. I think I'm going to buy a spare hanger ... just in case :-)

I know that Wheels Mfg. makes and sells them. Is that who you'd recommend?

[Cicli]

Thanks for all the responses, folks. A lot of useful information was provided. I think I'm going to buy a spare hanger ... just in case :-)

I know that Wheels Mfg. makes and sells them. Is that who you'd recommend?

I personally like the OE ones. I am not for buying a stronger hanger than stock. I want it to give up and not take the dropout with it.
I have a friend that got a steel one for his plastic wonder bike. Maybe it was because the factory guys used them. They dont have to worry too muck about the frame though.

[bikinchris]

I have changed a lot of hangers over the years. I have never seen one spontaneously break. I am not afraid of aligning them in the least. A simple visual check for cracks after the alignment is a good idea to see if you bent it too far.

[John H.]

I have seen a lot of bad hangers.
A few years ago it seemed like every Specialized Tarmac came out of the box with a misaligned hanger.
And it was even money that the replacement hanger would also be bad.
Same for Santa Cruz.

[fuzzalow]

No. Derailleur hangers do not spontaneously break.

However, drummers for the rock band Spinal Tap have been know to spontaneously combust.

https://table9mutant.files.wordpress.com/2015/02/spinal-tap-drummer.gif

[Cicli]

No. Derailleur hangers do not spontaneously break.

However, drummers for the rock band Spinal Tap have been know to spontaneously combust.

https://table9mutant.files.wordpress.com/2015/02/spinal-tap-drummer.gif

Tragic gardening accidents too.

[cachagua]

They absolutely weaken when they're aligned. You're bending them enough that they take a new shape. (Some Mech E. can tell us the correct term for this.) Big difference from frame flex..

What we call frame flex is elastic deformation -- basically it's temporary; when the load is removed everything snaps back to its original shape. Permanent bending, on the other hand, is called plastic deformation.

Full disclosure: I'm not a MechE, I'm a language fetishist.

[Ronsonic]

It's funny how bikes that don't have replaceable hangers tend to never have any trouble with them...

Never had any issues with my Ti Serotta that just had a beefy Ti hanger built into the dropout. No issues with my All City Space Horse that is pretty much the same thing just steel.


Non-replaceable hangers are sturdy things. The guys who designed them knew they had to be. They weren't replaceable. Those are very sturdy compared to a lot of the replaceable ones out there. I've seen and owned hangers that seemed to be die cast pot metal and others that are CNC billet. Big differences in quality out there. Some it wouldn't bother me to tweak an alignment on. But others look like they'll crumble with a hard look.

It sounds like you've had good ones.

[adub]

Ive had a hanger go out of alignment/bend knowing I didn't drop the bike. A real head scratcher.

[lhuerta]

...but I was recently told by a mechanic at one of the LBSs that it could happen. Hence, he likes to avoid adjusting/aligning them out of fear that, if they don't break during alignment, they may break on the road, leaving the customer stranded..


Oy! Run, don't walk as far as you can from this so-called "mechanic" and don't ever let him touch your bike again.

Any mechanic knows that every replaceable der hanger MUST be aligned upon installation to a bike. Hangers are not matched to the alignment of your dropouts, thus they must be aligned (with correct tool, not eye-balling) to match the specific/unique dropout on which they will hang. There is simply no such thing as a der hanger pre-aligned to your bike upon installation.

As for spontaneous combustion and re-ailingment...for catastrophic failure to occur the hanger must have been compromised earlier, either from bike falling on drive side, ham-fisted alignment to begin with, etc. If a hanger needs to be re-aligned it must be done so carefully and fully inspected for micro cracks or discoloration that reveal it has been comprised....if you spot any then the hanger is trash.

The best insurance is to dump your OEM hanger, most of which are cheap stamped alum, and get a robust CNC hanger like those offered by Wheels Manufacturing. And always carry a spare in your tool pouch, but remember to pre-align the spare to your dropouts before you place it in your pouch.