DANGER: Trek multitrack 7300 (hybrid) aluminum bracket sheers off, rips apart entire rear end of bik

[Peter Cole]

David L. Johnson wrote:
> On Sun, 27 Mar 2005 21:16:11 -0600, Dan wrote:

> >
> > Saturday afternoon I was riding along a clean flat nature trail; no
> > sticks in the gears, no nothing. I was going at an even speed of
> > about 20-25mph in the next-highest gear when all of a sudden I hear
a
> > *SNAP*, then something smashed into the rear spokes, causing an
almost
> > instant stop. I was lucky I wasn't going downhill when this
occurred,
> > or I would've flown over the handlebars.
> >
> > It turns out that a small piece of the aluminum frame supporting
the
> > gear shifter wore out due to metal fatigue.
>
> How do you figure this was due to metal fatigue? I assume that this
small
> piece of aluminum is the derailleur hanger, which is not subject to a
lot
> of stress under normal use. In order to claim some sort of fault of
the
> manufacturer, you have to be able to convince them that this was the
cause
> of the problem. The rest of the damage was collateral.
>
> In my experience, derailleurs usually snap off either because the
chain
> dropped and got tangled in the pulleys, which then twisted the
derailleur
> off since you were still applying pressure to the pedals, or there
was a
> missed shift under load, causing essentially the same chain of
events. I
> have seen both of these occur, one on the flat, and

Other things can cause this, like a chain jammed by a stone or stick. I
had an identical mishap a few years ago, trashing my r derailer,
hanger, and several spokes. Everything was so mangled it was impossible
to differentiate cause from effect. Like the OP, I was "just riding
along", fast, on a flattish trail -- well adjusted/maintained
drivetrain, yadda, yadda.

 

[Keith Rickert]

In article <[email protected]>,
"David L. Johnson" <[email protected]> wrote:

> On Sun, 27 Mar 2005 21:16:11 -0600, Dan wrote:
>
> > Hi,
> >
> > Because this is a hybrid I'm not sure whether to place it in racing or
> > off-road. But here goes my story.
>
> *.racing trimmed off as irrelevant.
> >
> > Saturday afternoon I was riding along a clean flat nature trail; no
> > sticks in the gears, no nothing. I was going at an even speed of
> > about 20-25mph in the next-highest gear when all of a sudden I hear a
> > *SNAP*, then something smashed into the rear spokes, causing an almost
> > instant stop. I was lucky I wasn't going downhill when this occurred,
> > or I would've flown over the handlebars.
> >
> > It turns out that a small piece of the aluminum frame supporting the
> > gear shifter wore out due to metal fatigue.
>
> How do you figure this was due to metal fatigue? I assume that this small
> piece of aluminum is the derailleur hanger, which is not subject to a lot
> of stress under normal use. In order to claim some sort of fault of the
> manufacturer, you have to be able to convince them that this was the cause
> of the problem. The rest of the damage was collateral.
>
> In my experience, derailleurs usually snap off either because the chain
> dropped and got tangled in the pulleys, which then twisted the derailleur
> off since you were still applying pressure to the pedals, or there was a
> missed shift under load, causing essentially the same chain of events. I
> have seen both of these occur, one on the flat, and the other (the
> missed-shift then crunch) on a short, steep climb. One other possibility
> that can occur is if you shift it into the spokes, which is caused by a
> misadjusted derailleur. However, I don't imagine this was the cause due
> to the circumstances you describe.

The other cause that I've seen has been either picking up a stick
(mountain biking) or (happened to me) wheel reflector comes partly
loose, twists sideways, and takes out the derailleur along the way.

Keith

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[Keith Rickert]

In article <[email protected]>,
"David L. Johnson" <[email protected]> wrote:

> On Sun, 27 Mar 2005 21:16:11 -0600, Dan wrote:
>
> > Hi,
> >
> > Because this is a hybrid I'm not sure whether to place it in racing or
> > off-road. But here goes my story.
>
> *.racing trimmed off as irrelevant.
> >
> > Saturday afternoon I was riding along a clean flat nature trail; no
> > sticks in the gears, no nothing. I was going at an even speed of
> > about 20-25mph in the next-highest gear when all of a sudden I hear a
> > *SNAP*, then something smashed into the rear spokes, causing an almost
> > instant stop. I was lucky I wasn't going downhill when this occurred,
> > or I would've flown over the handlebars.
> >
> > It turns out that a small piece of the aluminum frame supporting the
> > gear shifter wore out due to metal fatigue.
>
> How do you figure this was due to metal fatigue? I assume that this small
> piece of aluminum is the derailleur hanger, which is not subject to a lot
> of stress under normal use. In order to claim some sort of fault of the
> manufacturer, you have to be able to convince them that this was the cause
> of the problem. The rest of the damage was collateral.
>
> In my experience, derailleurs usually snap off either because the chain
> dropped and got tangled in the pulleys, which then twisted the derailleur
> off since you were still applying pressure to the pedals, or there was a
> missed shift under load, causing essentially the same chain of events. I
> have seen both of these occur, one on the flat, and the other (the
> missed-shift then crunch) on a short, steep climb. One other possibility
> that can occur is if you shift it into the spokes, which is caused by a
> misadjusted derailleur. However, I don't imagine this was the cause due
> to the circumstances you describe.

The other cause that I've seen has been either picking up a stick
(mountain biking) or (happened to me) wheel reflector comes partly
loose, twists sideways, and takes out the derailleur along the way.

Keith

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[[email protected]]

Weisse Luft wrote:
> Sounds like a break-away hanger. These are designed to break in
order
> to save the frame. Sounds like you got something like a small stone
> caught in the chain, causing the derailer to grab the chain and
> pedaling caused the whole derailer to ride up and over, breaking the
> mount AS DESIGNED.

Good point. Unfortunately, it sounds like the failure caused more
collateral damage than just the hanger breaking away, and that the
repairs will cost more than the bicycle is worth.

Sheldon's shop sells replacement hangers, see
"http://www.sheldonbrown.com/harris/hangers/"

With a steel or titanium frame, if the hanger is subject to stress, it
bends, and it can usually be bent back (a limited number of times),
plus it usually won't fail catastrophically (you'll have trouble
shifting, and notice that it is bent). With aluminum, the hanger will
break off, rather than bend, so the hangers are replaceable, at least
on the higher end models, but you run the danger of the collateral
damage to both the bicycle and the rider.

In any case, the orginal poster is not likely to get anything from
Trek. If it was a breakaway hanger, that behaved as designed, Trek
isn't going to cover the collateral damage. If it's on non-replaceable
hanger, then Trek will state that their lower end models don't have all
the features of the higher end models, and that's a risk that the owner
takes.

 

[Bob Schwartz]

In rec.bicycles.racing [email protected] wrote:
> Dan wrote:

> <snip>

>> It turns out that a small piece of the aluminum frame supporting the
>> gear shifter wore out due to metal fatigue. The shifter mechanism
>> ripped off the aluminum frame, got caught in the rear spokes, and
>> destroyed the entire rear end of the bike. Several spokes are broken
>> and/or bent. The shifter mechanism is bent in several places, the
>> shifter wire is shredded, and the front crank apparatus also has some
>> damage due to the sudden awkward pull on the chain.

> I would be willing to bet that the manufacturer finds an excuse to not
> do anything, even if the dealer goes to bat for you. It doesn't matter
> what the actual cause of the failure was, it's whether or not they can
> find a way to not do anything, since it's your word against their's.

Look, it was his own damn fault. Frames don't fail that way without
some measure of operator error. He should suck it up and buy a new
bike or frame and not expect Trek to cover for his mistakes.

> You really want to avoid aluminum frames if at all possible, but you're
> not going to find many $420 bicycles with chromoloy steel frames! Metal
> fatigue is a huge problem with aluminum, and not just on bicycles. Of
> course most of the time you'll be just fine, but it's those
> catastrophic failures, that are much more likely to occur with
> aluminum, that are scary. The derailleur hanger can be subjected to a
> lot of stress, with not a lot of metal there.

This is flat out ********.

I've broken my share of bikes. The really hairy frame failures have
all involved steel. The only damage I've done to any of the aluminum
bikes I've owned was my own damn fault.

The time I ripped the down tube out of the lower head lug in a crit,
it was a steel frame. The time I had a chain stay come loose from
the bottom bracket shell, it was steel. The time I was wondering
what the !@#$% was up with my front brake and realized, once I had
stopped, that the fork leg was failing at the crown, it was steel.

And the time I crashed and whacked an aluminum derailleur hanger, I
fixed it with a cresent wrench and an alignment tool. If it would
have failed later I'd have sucked it up and bought a new frame
because it would have been my own damn fault.

Derailleur hangers do not see a lot of stress unless someone screws
up.

Bob Schwartz
[email protected]

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[[email protected]]

Werehatrack wrote:
> On Wed, 30 Mar 2005 07:14:36 CST, "Phil, Squid-in-Training"
> <[email protected]> may have said:
>
> >[email protected] wrote:
> >> Your bike sounds like a prime candidate to become a singlespeed.
> >
> >LOL nice way to look at it...
>
> If half the right dropout is gone, it's not much of a candidate for
> conversion until the dropout has been replaced. (Not to mention the
> possible bent stays.)
>
> --

I figured he snapped off part of the hanger. Half of the dropout would
be impressive.
Bent aluminum stays? Really? You think?
/s

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[[email protected]]

Bob Schwartz wrote:

> Look, it was his own damn fault. Frames don't fail that way without
> some measure of operator error.

If it was a replaceable, breakaway hanger, there was no frame failure,
the hanger broke away as it was designed to do. Unfortunately, after it
broke was when the real damage occurred, but you can't expect the
manufacturer to cover collateral damage like that.

> He should suck it up and buy a new
> bike or frame and not expect Trek to cover for his mistakes.

I agree that he will have to buy a new bike, and that it is
unreasonable for Trek to cover the damage, if in fact it was a
replaceable, breakaway hanger that broke off.

> This is flat out ********.
>
> I've broken my share of bikes. The really hairy frame failures have
> all involved steel. The only damage I've done to any of the aluminum
> bikes I've owned was my own damn fault.

Your personal experience is not proof of anything.

Aluminum is not designed to be stressed. The clever workaround is the
replaceable, breakaway, derailleur hanger, which is designed to prevent
frame damage. As the orignal poster found, things don't always fail in
the perfect manner. Aluminum has some good attributes, it's light and
it's cheap. But in some cases, it's better to have something bendable
than breakable.

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[[email protected]]

[email protected] wrote:
>
>
> Your personal experience is not proof of anything.
>
> Aluminum is not designed to be stressed. The clever workaround is the
> replaceable, breakaway, derailleur hanger, which is designed to
prevent
> frame damage. As the orignal poster found, things don't always fail
in
> the perfect manner. Aluminum has some good attributes, it's light and
> it's cheap. But in some cases, it's better to have something bendable
> than breakable.

"Aluminum is not designed to be stressed!" IOW, we should all
rush out and get good solid steel parts to replace our aluminum frames.
And aluminum cranks. And aluminum brakes. And aluminum derailleurs.
And handlebars. And stems. And rims. And hubs. And seatposts...

Sadly, I don't think your posts have anything to do with April First!


- Frank Krygowski

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[[email protected]]

Don't made bikes made in asia if you care about safety. Buy
cannondale or american made.

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[Robert Chung]

Bob Schwartz wrote:
> Look, it was his own damn fault. Frames don't fail that way without
> some measure of operator error. He should suck it up and buy a new
> bike or frame and not expect Trek to cover for his mistakes.

Several years ago, while JRA, I ran over a stick (or perhaps, a vicious
and wily stick jumped up and attacked my innocent rear wheel). It lodged
into the wheel and ripped the derailleur out of the rear hanger, bent the
aluminum hanger, broke one spoke and bent a couple of others. I consider
that my own damn fault, not the manufacturer's.

Dan complained:
> I was not happy. I had to walk 8 miles home while contending
> with a pair of minor stress fractures in the legs

Poor baby. I took out my CPR-9, removed the broken derailleur, shortened
the chain to turn the bike into a single-speed, and did a rough true of
the wheel. Then I rode 10 miles home.


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[Curtis L. Russell]

On Sat, 2 Apr 2005 00:44:30 CST, [email protected] wrote:

>Don't made bikes made in asia if you care about safety. Buy
>cannondale or american made.

Who the **** added rbr to these posts and let the tech nuts loose? If
you're riding like a townie and the shifter breaks, you either need to
learn to shift or take the bike back to the shop when it starts to
make the funny grinding noises. If you claim to be able to do all that
and are riding hard, then you need to learn that **** happens and its
part of the game.

I had a really bad day once, making the mistake of riding the day
after high school graduation. Even with dodging and trying to look
ahead until I was blind, I managed to go through two spares and the
four patches I had. Hitched a ride home in the back of migrant
worker's pick-up truck. Didn't sue the bike shop for not telling me
tires get flats, didn't sue Budweiser for making cheap ass bottles and
didn't sue Cheng Shin for the tubes. I did give the migrant worker a
six pack in cans...

Curtis L. Russell
Odenton, MD (USA)
Just someone on two wheels...

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[Steven Scharf]

"Andy M-S" <[email protected]> wrote in message news:<[email protected]>...
> Excellent point. People who are used to steel frames will bend back
> derailer hangers; you can't do that with aluminum once it's been
> damaged. If the hanger had ever been bent back, that could weaken it
> to the point where failure might be possible.

> BTW, this is why the Trek aluminum frames generally include
> *replaceable* derailler hangers...if you bend it, you can replace
> it--usually two or three small screws fasten the hanger to the frame.

It might even be wise to replace it every few years as preventative
maintenance. I know that on one of my folding bicycles (Brompton),
they recommend periodic replacement of the aluminum handlebars, and
they offer a reinforcing brace too. Some owners have fitted steel
handlebars, after having fatigue failures of the aluminum ones. There
are some components that need to be designed with plenty of margin if
you're going to use aluminum (or make the component easily replaceable
like the break-away hangers).

 

[Michael J. Klein]

On Sat, 2 Apr 2005 00:44:30 CST, [email protected] wrote:

>Don't made bikes made in asia if you care about safety. Buy
>cannondale or american made.

I hate to tell you this, but I have been in a few Taiwan bicycle
factories where they asked me not to photograph the "American made"
frames they were building. More than 90% of the world's highest bike
technology comes from a small corridor in Taiwan, part of Taichung.

China is a different matter altogether.

Michael J. Klein [email protected]
Yangmei Jen (Hukou), Taoyuan Hsien, Taiwan, ROC
Please replace mousepotato with asiancastings
---------------------------------------------

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[[email protected]]

Cannondale is still made in USA and my 2002 lemond was also made in
usa.

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[[email protected]]

Cannondale is still made in USA and my 2002 lemond was also made in
usa.

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[[email protected]]

Cannondale is still made in USA and my 2002 lemond was also made in
usa.

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[[email protected]]

Cannondale is still made in USA and my 2002 lemond was also made in
usa.

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[Mark Hickey]

"Michael J. Klein" <[email protected]> wrote:

>On Sat, 2 Apr 2005 00:44:30 CST, [email protected] wrote:
>
>>Don't made bikes made in asia if you care about safety. Buy
>>cannondale or american made.
>
>I hate to tell you this, but I have been in a few Taiwan bicycle
>factories where they asked me not to photograph the "American made"
>frames they were building. More than 90% of the world's highest bike
>technology comes from a small corridor in Taiwan, part of Taichung.
>
>China is a different matter altogether.

Yes, in China, they don't want you to photograph the "Taiwan made"
bicycles. (I'm not kidding).

Mark Hickey
Habanero Cycles
http://www.habcycles.com
Home of the $695 ti frame

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[Steven M. Scharf]

<[email protected]> wrote in message
news:[email protected]...
> Cannondale is still made in USA and my 2002 lemond was also made in
> usa.

The manufacturing location doesn't guarantee anything. Cannondale has had
plenty of frame failures, and recalls of their frames. Honda has recalled
their aluminum framed motorcycles, year after year.

"http://www.cannondale.com/bikes/tech/recall-114903.html"
"http://www.mcnews.com/anforum/topic.asp?TOPIC_ID=85957&whichpage=2"
"http://www.marinbikes.com/recall/"
"http://www.cpsc.gov/cpscpub/prerel/prhtml04/04113.html"

"http://www.rivendellbicycles.com/html/101_framematerials.html"

There is just no way around the inherent properties of aluminum. Frame
failures are rare, but far greater, on a percentage basis, than on steel
frames.

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[Peter Cole]

Steven M. Scharf wrote:

> There is just no way around the inherent properties of aluminum.
Frame
> failures are rare, but far greater, on a percentage basis, than on
steel
> frames.

You have any real data to back up that claim?

<http://www.sheldonbrown.com/rinard/EFBe/frame_fatigue_test.htm>

If you're interested, perhaps you should study some material science,
it's a prerequisite to understanding frame design.