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



D

Dan

Guest
Hi,

Because this is a hybrid I'm not sure whether to place it in racing or
off-road. But here goes my story.

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. 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 was not happy. I had to walk 8 miles home while contending with a
pair of minor stress fractures in the legs (I was biking because I
can't run for the moment). I've contacted the dealer but so far no
reply. This $420 bike is just barely over 2 years old, with less than
500 miles on it. I expected to get more than a dollar per mile for
this bike, and I'm really not happy with Trek's poor design of this
frame and model.

If the dealer or Trek will support the repair of this obvious
manufacturer's defect, I will keep you apprised.

Dan

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What's a "shifter mechanism", is it different than "gear shifter"? I
guess the "shifter wire" is just the cable and the "front crank
apparatus" is just the crank.

So in other words the rear derailer hanger broke off, the derailer got
caught in the rear wheel, a few spokes broke and you've got a bent
chainwheel.
 
Dan:

You cite the cause as "metal fatigue," but that *may* be premature.
The problem you note is not that uncommon (derailer goes into the
spokes), though the circumstances under which you experienced *were*.
Uusually, the rider shifts to the lowest gear (closest to the wheel) in
back and the rear derailer, the stops of which have not been correctly
set, smashes into the spokes.

It's really, REALLY unlikely that the derailer hanger (I think that's
what you are describing) failed initially and caused the rest of the
event.

What is the year and model of the bike? I ask because I want to know
if it has a "rapid rise" rear derailer. In that case, it's just barely
possible that the "snap" you heard was a cable letting go. If that is
the case, given your reported speed, the RD would have been pulled back
suddenly to the closest-to-the-spokes position, and could have smacked
into the spokes. That could have broken the derailer hanger. But
that's all speculation, based on it being that kind of RD.

(I assume from your description that the accident stopped you
*immediately*--in essence, that the rear wheel started to skid, as if
you had a locked rear brakes.)

Beware of describing this to your LBS as an "obvious manufacturer's
defect" and talking about "Trek's poor design," etc. Those sort of
statements will almost immediately place you in their mind as a
"JRA"--the sort of person who brings in a thoroughly trashed bike and
complains that they were "Just Riding Along" when the wheels fell off,
the handlebar fell off, the frame split in half, etc. LBSes generally
don't deal well with this kind of situation--it sounds like you're
preparing for a lawsuit.

Instead, take the bike in and explain the symptoms, then ask them what
*they think* happened. If it's a half-decent shop, this can be a very
positive experience.

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.
>
> 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. 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 was not happy. I had to walk 8 miles home while contending with a
> pair of minor stress fractures in the legs (I was biking because I
> can't run for the moment). I've contacted the dealer but so far no
> reply. This $420 bike is just barely over 2 years old, with less

than
> 500 miles on it. I expected to get more than a dollar per mile for
> this bike, and I'm really not happy with Trek's poor design of this
> frame and model.
>
> If the dealer or Trek will support the repair of this obvious
> manufacturer's defect, I will keep you apprised.
>
> Dan
>
> --
> rec.bicycles.off-road is moderated by volunteers. To find help

solving
> posting problems, or contact the moderators, please see

http://rbor.org/
> Please read the charter before posting:

http://rbor.org/rbor_charter.txt
 
On 28 Mar 2005 04:41:43 -0800, "Andy M-S" <[email protected]>
wrote:

>Usually, the rider shifts to the lowest gear (closest to the wheel) in
>back and the rear derailer, the stops of which have not been correctly
>set, smashes into the spokes.


I had been in the same gear for about an eighth of a mile before it
occurred. It was a very normal, straight length of trail and was
cruising normally.

>It's really, REALLY unlikely that the derailer hanger (I think that's
>what you are describing) failed initially and caused the rest of the
>event.


I will show a picture of the aluminum support torn off the frame.
It's fuzzy but the blue part is the piece of the frame that's ripped
off. Is it normal for the derailer support to rip off the frame?

http://home.ptd.net/~vstevans/web/bike.jpg

>What is the year and model of the bike? I ask because I want to know
>if it has a "rapid rise" rear derailer. In that case, it's just barely
>possible that the "snap" you heard was a cable letting go. If that is
>the case, given your reported speed, the RD would have been pulled back
>suddenly to the closest-to-the-spokes position, and could have smacked
>into the spokes. That could have broken the derailer hanger. But
>that's all speculation, based on it being that kind of RD.


The cable is still in place on the derailer (albeit the sheathing and
hair of steel are protruding in places from going around the wheel).
Even so, I cannot believe that a cable stuck in the gears would rip
apart the aluminum frame of the bicycle.

I sounded like I was ready for a lawsuit because I figured this would
be like trying to talk to a car dealer..."we're out of warranty, so
tough luck". And I was seriously considering buying a road bike for
the summer :(

Dan
 
On 28 Mar 2005 04:41:43 -0800, "Andy M-S" <[email protected]>
wrote:

>What is the year and model of the bike? I ask because I want to know
>if it has a "rapid rise" rear derailer.


It was purchased in late 2002 (November). It's a Trek multitrack 7300
hybrid (blue)

Dan
 
If it has a rapid rise derailleur, the initial snap you heard may be
that a corroded cable broke, or the screw that clamps the cable to the
derailleur may have let go. Either case would send the derailleur
toward the spokes. If the stop wasn't set properly, it might then
slam into the spokes and do all the things that happened.

It is possible for the bike to shift normally even though the stops on
the derailleur are not set properly. In the case of a rapid-rise
derailleur, the shifter lets cable out to shift toward the bigger cog.
If the cable were adjusted so that the shifter stops the derailleur
instead of the stop screw stopping the derailleur, a sudden release of
the cable could cause the derailleur to go beyond its normal range.

Of course, if it isn't a rapid rise derailleur, none of this is your
problem.
 

>If the dealer or Trek will support the repair of this obvious
>manufacturer's defect, I will keep you apprised.


It is not at all obvious that this is a manufacturer's defect.
Misadjustment combined with cable failure could easily cause this sort
of thing to happen.
 
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.
>
> 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. 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 was not happy. I had to walk 8 miles home while contending with a
> pair of minor stress fractures in the legs (I was biking because I
> can't run for the moment). I've contacted the dealer but so far no
> reply. This $420 bike is just barely over 2 years old, with less than
> 500 miles on it. I expected to get more than a dollar per mile for
> this bike, and I'm really not happy with Trek's poor design of this
> frame and model.
>
> If the dealer or Trek will support the repair of this obvious
> manufacturer's defect, I will keep you apprised.
>
> Dan
>



Dan,

Given that TREK uses CAD/CAM and extensive quality control to design its
bikes, the metal fatigue on the derailleur hanger was most likely due to
damage that occurred in shipping or when the 16 year old mechanic who
put the bike together at the shop you got it from took it for a spin and
mashed it against a curb or something (believe it or not teenagers who
make minimum wage do stupid stuff like that).

One of the most common things in a crash is for the derailluer hanger to
get bent. And the way most people "fix" it is to bend it back, not
realizing that doing so causes substantial yet invisible metal fatigue.

So calm down on the CONSUMER PRODUCT WARNING thing unless you know for a
fact that defect originated in the manufacturing process.

Thanks,

Magilla

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"Dan" <[email protected]> wrote in message
news:[email protected]...
> Hi,
>
> Because this is a hybrid I'm not sure whether to place it in racing or
> off-road. But here goes my story.
>
> 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. 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 was not happy. I had to walk 8 miles home while contending with a
> pair of minor stress fractures in the legs (I was biking because I
> can't run for the moment). I've contacted the dealer but so far no
> reply. This $420 bike is just barely over 2 years old, with less than
> 500 miles on it. I expected to get more than a dollar per mile for
> this bike, and I'm really not happy with Trek's poor design of this
> frame and model.
>
> If the dealer or Trek will support the repair of this obvious
> manufacturer's defect, I will keep you apprised.
>
> Dan
>


Thank God it wasn't a Bianchi.

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Andy M-S wrote:
> 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.


Waah, waah, waah... Tweaks on a new bike like the OP's wouldn't cause
fatigue failure on a derailleur hangar. If it were twisted 360 degrees,
however, of course it would have a problem.

The aluminum derailleur hangar is not going to fail spontaneously under use,
even if it's bent back several times. It sounds like you're reading from a
book and not from experience. Shifting parts are nowhere nearly as stressed
as frames are.
--
Phil, Squid-in-Training
 
Well, I did say "could." I've seen bent aluminum parts fail pretty
spectacularly, including a reflector mount that was carrying a small
headlight. But that's as may be...

In any event, the puzzler here--and the reason I started off a response
with thinking this might be a rapid-rise type derailer--is that the OP
states he was in a pretty high gear (and trucking along at 20-25 on a
Hybrid, if we accept his figures).

That would argue strongly that the derailer was well away from the
spokes. Typical causes for this kind of damage would be shifting
*into* the spokes, but that seems contraindicated here.

But a cable or shifter problem COULD lead a RR derailer to slam back
into the spokes, with all of the damage described.
 
Andy M-S wrote:
> Well, I did say "could." I've seen bent aluminum parts fail pretty
> spectacularly, including a reflector mount that was carrying a small
> headlight. But that's as may be...
>
> In any event, the puzzler here--and the reason I started off a
> response with thinking this might be a rapid-rise type derailer--is
> that the OP states he was in a pretty high gear (and trucking along
> at 20-25 on a Hybrid, if we accept his figures).
>
> That would argue strongly that the derailer was well away from the
> spokes. Typical causes for this kind of damage would be shifting
> *into* the spokes, but that seems contraindicated here.
>
> But a cable or shifter problem COULD lead a RR derailer to slam back
> into the spokes, with all of the damage described.


Agreed.
--
Phil, Squid-in-Training
 
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.
 
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.
>
> 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. 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 was not happy. I had to walk 8 miles home while contending with a
> pair of minor stress fractures in the legs (I was biking because I
> can't run for the moment). I've contacted the dealer but so far no
> reply. This $420 bike is just barely over 2 years old, with less

than
> 500 miles on it. I expected to get more than a dollar per mile for
> this bike, and I'm really not happy with Trek's poor design of this
> frame and model.
>
> If the dealer or Trek will support the repair of this obvious
> manufacturer's defect, I will keep you apprised.
>
> Dan
>
> --
> rec.bicycles.off-road is moderated by volunteers. To find help

solving
> posting problems, or contact the moderators, please see

http://rbor.org/
> Please read the charter before posting:

http://rbor.org/rbor_charter.txt

Your bike sounds like a prime candidate to become a singlespeed.

/s

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[email protected] wrote:
> 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.
>>
>> 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. 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 was not happy. I had to walk 8 miles home while contending with a
>> pair of minor stress fractures in the legs (I was biking because I
>> can't run for the moment). I've contacted the dealer but so far no
>> reply. This $420 bike is just barely over 2 years old, with less
>> than 500 miles on it. I expected to get more than a dollar per mile
>> for this bike, and I'm really not happy with Trek's poor design of
>> this frame and model.
>>
>> If the dealer or Trek will support the repair of this obvious
>> manufacturer's defect, I will keep you apprised.
>>
>> Dan
>>
>> --
>> rec.bicycles.off-road is moderated by volunteers. To find help
>> solving posting problems, or contact the moderators, please see
>> http://rbor.org/ Please read the charter before posting:

> http://rbor.org/rbor_charter.txt
>
> Your bike sounds like a prime candidate to become a singlespeed.


LOL nice way to look at it...

--
Phil, Squid-in-Training


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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.)

--
My email address is antispammed; pull WEEDS if replying via e-mail.
Typoes are not a bug, they're a feature.
Words processed in a facility that contains nuts.

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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.)

--
My email address is antispammed; pull WEEDS if replying via e-mail.
Typoes are not a bug, they're a feature.
Words processed in a facility that contains nuts.

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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.

Are you _sure_ you hadn't shifted at that point, or had the chain fall off
the chainring? I know it's easy for the dealer to just say it was
operator error and not take responsibility, but you need an explanation
why this was not the case here.


> If the dealer or Trek will support the repair of this obvious
> manufacturer's defect, I will keep you apprised.


Don't be surprised if the obviousness of the defect is missed by the
dealer. I don't see it, and would have to be convinced.

--

David L. Johnson

__o | A mathematician is a machine for turning coffee into theorems.
_`\(,_ | -- Paul Erdos
(_)/ (_) |


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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.

Are you _sure_ you hadn't shifted at that point, or had the chain fall off
the chainring? I know it's easy for the dealer to just say it was
operator error and not take responsibility, but you need an explanation
why this was not the case here.


> If the dealer or Trek will support the repair of this obvious
> manufacturer's defect, I will keep you apprised.


Don't be surprised if the obviousness of the defect is missed by the
dealer. I don't see it, and would have to be convinced.

--

David L. Johnson

__o | A mathematician is a machine for turning coffee into theorems.
_`\(,_ | -- Paul Erdos
(_)/ (_) |


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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.
 

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