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Main
Date: 13 Jun 2007 13:53:07
From: Kristian M Zoerhoff
Subject: Cannondale Mtn Bike Recall
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<http://www.cpsc.gov/cpscpub/prerel/prhtml07/07211.html >
"Cannondale Announces Recall of Mountain Bicycles;
Lefty Forks Can Break Unexpectedly"
--
__o Kristian Zoerhoff
_'\(,_ kristian.zoerhoff@gmail.com
(_)/ (_)
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Date: 18 Jun 2007 02:49:51
From: Thomas Hood
Subject: Re: Cannondale Mtn Bike Recall
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On Jun 16, 10:23 pm, jobst.bra...@stanfordalumni.org wrote:
> That may be, but the torque of a hub brake adds to the bending load on
> the strut that is supposed to telescope freely axially while
> supporting load and brake bending moments. I haven't seen a
> motorcycle with such a front end, but I'm sure there are some in the
> woodwork.
>
> Jobst Brandt- Hide quoted text -
>
> - Show quoted text -
Whilst we're on the subject, I saw one of these on the London-Brighton-
London yesterday:
http://www.use1.com/products/sub_antidive/sub_80mm_detail.php
http://www.use1.com/products/sub_antidive/detail.php
http://www.use1.com/products/sub_antidive/technical.php
I've no idea how it rides, or whether it's a valid concept, although I
did notice the shaft's anodizing was badly abraded where it enters the
upper. I pretty sure it had happened in an unacceptable mileage
judging by the general appearance of the bike (very new looking) and
the rider (very obese looking). The shafts on my Marzocchi fork (also
aluminium) appear much better coated/ sealed, as the bike gets ridden
in invariably filthy conditions (head-to-toe mud), and with no
maintenance at all the fork remains unblemished, smooth and holds air
for years at a time, which I find remarkable given my experience of
Rock Shox and and Manitou forks in years past.
It's always a good ride just to look at the weird and wonderful bikes
on display. I saw some guy pushing what appeared to be a genuine Lotus
bike (a la Chris Boardman) up Ditchling Beacon:
http://www.grouplotus.com/eng/track_record.php?section=17&page=25&id=13
I can't find a good page on these, which is surprising given their
iconic status (at least here in the UK), and don't know whether they
were mass produced or not.
Tom
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Date: 16 Jun 2007 11:49:48
From: Johnny Sunset
Subject: Re: Cannondale Mtn Bike Recall
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On Jun 16, 1:43 pm, Jobst Brandt wrote:
> Steve Gravrock writes:
>
> http://www.cpsc.gov/cpscpub/prerel/prhtml07/07211.html
>
> >>> "Cannondale Announces Recall of Mountain Bicycles; Lefty Forks Can
> >>> Break Unexpectedly"
> >> Of course that stupid design would be dangerous.
> > That was my reaction the first time I saw a Lefty, but now I'm not
> > so sure. It looks wrong because it's asymmetrical, but that's
> > actually not uncommon. Most modern forks have a spring in one leg
> > and dampening controls in the other. That includes basically all air
> > forks. The Lefty just combines both into a single leg. Supporting
> > the hub on one end also seems questionable at first, but it's common
> > on wheelchairs.
> > The CPSC announcement doesn't say exactly what went wrong, but I'd
> > guess that either the lower part of the fork leg separated from the
> > upper, or the fork leg separated from the steerer.
> > Does anyone know why Cannondale moved away from their old design
> > that put the suspension above the crown of what was otherwise a
> > rigid fork? That seemed pretty sensible to me, especially back in
> > the days when suspension fork flex due to uneven compression was a
> > major problem.
>
> Consider the difference between a cantilevered spindle, extending from
> a single fork leg and one that is supported on both ends with wheel
> bearings close to those ends. Bending loads from the cantilevered
> spindle are more than ten times as great and propagate up the fork
> leg that is otherwise not loaded in bending from the spindle.
>
> Looking at automobile wheel support, the size and design of axles and
> spindles support is done with care, having large transition radii and
> solid anchoring in housings and steering knuckles that do not look
> like the features visible on the Cannondale struts.
>
> What we need next is this design with a disk brake to make all the
> problems work together to enhance failures.
But the single-sided hub mounting eliminates the disc brake wheel/
ejection concern, even with the brake mounted on the rear of the mono-
strut.
--
Tom Sherman - Holstein-Friesland Bovinia
The weather is here, wish you were beautiful
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Date: 16 Jun 2007 21:23:54
From:
Subject: Re: Cannondale Mtn Bike Recall
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Tom Sherman writes:
http://www.cpsc.gov/cpscpub/prerel/prhtml07/07211.html
>>>>> "Cannondale Announces Recall of Mountain Bicycles; Lefty Forks
>>>>> Can Break Unexpectedly"
>>>> Of course that stupid design would be dangerous. That was my
>>>reaction the first time I saw a Lefty, but now I'm not so sure. It
>>>looks wrong because it's asymmetrical, but that's actually not
>>>uncommon. Most modern forks have a spring in one leg and dampening
>>>controls in the other. That includes basically all air forks. The
>>>Lefty just combines both into a single leg. Supporting the hub on
>>>one end also seems questionable at first, but it's common on
>>>wheelchairs.
>>> The CPSC announcement doesn't say exactly what went wrong, but I'd
>>> guess that either the lower part of the fork leg separated from
>>> the upper, or the fork leg separated from the steerer. Does
>>> anyone know why Cannondale moved away from their old design that
>>> put the suspension above the crown of what was otherwise a rigid
>>> fork? That seemed pretty sensible to me, especially back in the
>>> days when suspension fork flex due to uneven compression was a
>>> major problem.
>> Consider the difference between a cantilevered spindle, extending
>> from a single fork leg and one that is supported on both ends with
>> wheel bearings close to those ends. Bending loads from the
>> cantilevered spindle are more than ten times as great and propagate
>> up the fork leg that is otherwise not loaded in bending from the
>> spindle.
>> Looking at automobile wheel support, the size and design of axles
>> and spindles support is done with care, having large transition
>> radii and solid anchoring in housings and steering knuckles that do
>> not look like the features visible on the Cannondale struts.
>> What we need next is this design with a disk brake to make all the
>> problems work together to enhance failures.
> But the single-sided hub mounting eliminates the disc brake wheel/
> ejection concern, even with the brake mounted on the rear of the
> mono- strut.
That may be, but the torque of a hub brake adds to the bending load on
the strut that is supposed to telescope freely axially while
supporting load and brake bending moments. I haven't seen a
motorcycle with such a front end, but I'm sure there are some in the
woodwork.
Jobst Brandt
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Date: 16 Jun 2007 20:56:24
From: jim beam
Subject: Re: Cannondale Mtn Bike Recall
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jobst.brandt@stanfordalumni.org wrote:
> Tom Sherman writes:
>
> http://www.cpsc.gov/cpscpub/prerel/prhtml07/07211.html
>
>>>>>> "Cannondale Announces Recall of Mountain Bicycles; Lefty Forks
>>>>>> Can Break Unexpectedly"
>
>>>>> Of course that stupid design would be dangerous. That was my
>>>> reaction the first time I saw a Lefty, but now I'm not so sure. It
>>>> looks wrong because it's asymmetrical, but that's actually not
>>>> uncommon. Most modern forks have a spring in one leg and dampening
>>>> controls in the other. That includes basically all air forks. The
>>>> Lefty just combines both into a single leg. Supporting the hub on
>>>> one end also seems questionable at first, but it's common on
>>>> wheelchairs.
>
>>>> The CPSC announcement doesn't say exactly what went wrong, but I'd
>>>> guess that either the lower part of the fork leg separated from
>>>> the upper, or the fork leg separated from the steerer. Does
>>>> anyone know why Cannondale moved away from their old design that
>>>> put the suspension above the crown of what was otherwise a rigid
>>>> fork? That seemed pretty sensible to me, especially back in the
>>>> days when suspension fork flex due to uneven compression was a
>>>> major problem.
>
>>> Consider the difference between a cantilevered spindle, extending
>>> from a single fork leg and one that is supported on both ends with
>>> wheel bearings close to those ends. Bending loads from the
>>> cantilevered spindle are more than ten times as great and propagate
>>> up the fork leg that is otherwise not loaded in bending from the
>>> spindle.
>
>>> Looking at automobile wheel support, the size and design of axles
>>> and spindles support is done with care, having large transition
>>> radii and solid anchoring in housings and steering knuckles that do
>>> not look like the features visible on the Cannondale struts.
>
>>> What we need next is this design with a disk brake to make all the
>>> problems work together to enhance failures.
>
>> But the single-sided hub mounting eliminates the disc brake wheel/
>> ejection concern, even with the brake mounted on the rear of the
>> mono- strut.
>
> That may be, but the torque of a hub brake adds to the bending load on
> the strut that is supposed to telescope freely axially while
> supporting load and brake bending moments. I haven't seen a
> motorcycle with such a front end, but I'm sure there are some in the
> woodwork.
>
eh? you've never seen a vespa? only 10 million made since 1946.
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Date: 17 Jun 2007 07:09:23
From: =?ISO-8859-1?Q?G=FCnther?= Schwarz
Subject: Re: Cannondale Mtn Bike Recall
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jim beam wrote:
> jobst.brandt@stanfordalumni.org wrote:
>> Tom Sherman writes:
>>>>> Does
>>>>> anyone know why Cannondale moved away from their old design that
>>>>> put the suspension above the crown of what was otherwise a rigid
>>>>> fork? That seemed pretty sensible to me, especially back in the
>>>>> days when suspension fork flex due to uneven compression was a
>>>>> major problem.
Limited travel for MTBs and probably in comparison to mass produced
standard forks just to expensive for touring cycles. The design
principle survives in a bike with limited space in the area of the fork
blades: Speed machine by HP-Velotechnik.
>>>> Consider the difference between a cantilevered spindle, extending
>>>> from a single fork leg and one that is supported on both ends with
>>>> wheel bearings close to those ends. Bending loads from the
>>>> cantilevered spindle are more than ten times as great and propagate
>>>> up the fork leg that is otherwise not loaded in bending from the
>>>> spindle.
You're writing here about completely different designs, right? Headshock
vs. Lefty Monofork.
>> That may be, but the torque of a hub brake adds to the bending load
>> on the strut that is supposed to telescope freely axially while
>> supporting load and brake bending moments. I haven't seen a
>> motorcycle with such a front end, but I'm sure there are some in the
>> woodwork.
>>
>
> eh? you've never seen a vespa? only 10 million made since 1946.
8" wheels and thus extremely short fork blades.
Günther
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Date: 16 Jun 2007 00:15:33
From: SMS
Subject: Re: Cannondale Mtn Bike Recall
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Kristian M Zoerhoff wrote:
> <http://www.cpsc.gov/cpscpub/prerel/prhtml07/07211.html>
>
> "Cannondale Announces Recall of Mountain Bicycles;
> Lefty Forks Can Break Unexpectedly"
A relative that knows I have many bicycle called me this morning to
inform me of this recall. I'd never buy a Cannondale in million years,
and bizzarro designs like the one sided fork are one of the reasons.
Carbon cranksets are also being recalled.
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Date: 15 Jun 2007 20:44:33
From: Fritz
Subject: Re: Cannondale Mtn Bike Recall
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On Wed, 13 Jun 2007 13:53:07 GMT, Kristian M Zoerhoff
<kristian.zoerhoff@gmail.com > wrote:
><http://www.cpsc.gov/cpscpub/prerel/prhtml07/07211.html>
>
>"Cannondale Announces Recall of Mountain Bicycles;
>Lefty Forks Can Break Unexpectedly"
Of course that stupid design would be dangerous.
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Date: 16 Jun 2007 16:26:37
From: Steve Gravrock
Subject: Re: Cannondale Mtn Bike Recall
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On 2007-06-16, Fritz <kh6zv9@yahoo.com > wrote:
> On Wed, 13 Jun 2007 13:53:07 GMT, Kristian M Zoerhoff
><kristian.zoerhoff@gmail.com> wrote:
>
>><http://www.cpsc.gov/cpscpub/prerel/prhtml07/07211.html>
>>
>>"Cannondale Announces Recall of Mountain Bicycles;
>>Lefty Forks Can Break Unexpectedly"
>
> Of course that stupid design would be dangerous.
That was my reaction the first time I saw a Lefty, but now I'm not so
sure. It looks wrong becuase it's asymmetrical, but that's actually not
uncommon. Most modern forks have a spring in one leg and dampening
controls in the other. That includes basically all air forks. The Lefty
just combines both into a single leg. Supporting the hub on one end
also seems questionable at first, but it's common on wheelchairs.
The CPSC announcement doesn't say exactly what went wrong, but I'd
guess that either the lower part of the fork leg separated from the
upper, or the fork leg separated from the steerer.
Does anyone know why Cannondale moved away from their old design that
put the suspension above the crown of what was otherwise a rigid fork?
That seemed pretty sensible to me, especially back in the days when
suspension fork flex due to uneven compression was a major problem.
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Date: 16 Jun 2007 18:43:26
From:
Subject: Re: Cannondale Mtn Bike Recall
|
Steve Gravrock writes:
http://www.cpsc.gov/cpscpub/prerel/prhtml07/07211.html
>>> "Cannondale Announces Recall of Mountain Bicycles; Lefty Forks Can
>>> Break Unexpectedly"
>> Of course that stupid design would be dangerous.
> That was my reaction the first time I saw a Lefty, but now I'm not
> so sure. It looks wrong because it's asymmetrical, but that's
> actually not uncommon. Most modern forks have a spring in one leg
> and dampening controls in the other. That includes basically all air
> forks. The Lefty just combines both into a single leg. Supporting
> the hub on one end also seems questionable at first, but it's common
> on wheelchairs.
> The CPSC announcement doesn't say exactly what went wrong, but I'd
> guess that either the lower part of the fork leg separated from the
> upper, or the fork leg separated from the steerer.
> Does anyone know why Cannondale moved away from their old design
> that put the suspension above the crown of what was otherwise a
> rigid fork? That seemed pretty sensible to me, especially back in
> the days when suspension fork flex due to uneven compression was a
> major problem.
Consider the difference between a cantilevered spindle, extending from
a single fork leg and one that is supported on both ends with wheel
bearings close to those ends. Bending loads from the cantilevered
spindle are more than ten times as great and propagate up the fork
leg that is otherwise not loaded in bending from the spindle.
Looking at automobile wheel support, the size and design of axles and
spindles support is done with care, having large transition radii and
solid anchoring in housings and steering knuckles that do not look
like the features visible on the Cannondale struts.
What we need next is this design with a disk brake to make all the
problems work together to enhance failures.
Jobst Brandt
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Date: 16 Jun 2007 19:08:19
From: Steve Gravrock
Subject: Re: Cannondale Mtn Bike Recall
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On 2007-06-16, jobst.brandt@stanfordalumni.org
<jobst.brandt@stanfordalumni.org > wrote:
> Consider the difference between a cantilevered spindle, extending from
> a single fork leg and one that is supported on both ends with wheel
> bearings close to those ends. Bending loads from the cantilevered
> spindle are more than ten times as great and propagate up the fork
> leg that is otherwise not loaded in bending from the spindle.
That makes sense. I'd thought about it only in terms of the load on the
hub bearings. It seems like that increased bending load could
contribute to the crowns breaking, if that's indeed what happened.
> What we need next is this design with a disk brake to make all the
> problems work together to enhance failures.
It looks like all of Cannondale's current mountain bikes come with disk
brakes, including Lefty-equipped models.
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Date: 16 Jun 2007 18:29:11
From:
Subject: Re: Cannondale Mtn Bike Recall
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Steve Gravrock writes:
http://www.cpsc.gov/cpscpub/prerel/prhtml07/07211.html
>>> "Cannondale Announces Recall of Mountain Bicycles; Lefty Forks Can
>>> Break Unexpectedly"
>> Of course that stupid design would be dangerous.
> That was my reaction the first time I saw a Lefty, but now I'm not
> so sure. It looks wrong because it's asymmetrical, but that's
> actually not uncommon. Most modern forks have a spring in one leg
> and dampening controls in the other. That includes basically all air
> forks. The Lefty just combines both into a single leg. Supporting
> the hub on one end also seems questionable at first, but it's common
> on wheelchairs.
> The CPSC announcement doesn't say exactly what went wrong, but I'd
> guess that either the lower part of the fork leg separated from the
> upper, or the fork leg separated from the steerer.
> Does anyone know why Cannondale moved away from their old design
> that put the suspension above the crown of what was otherwise a
> rigid fork? That seemed pretty sensible to me, especially back in
> the days when suspension fork flex due to uneven compression was a
> major problem.
Consider the difference between a cantilevered spindle, extending from
a single fork leg and one that is supported on both ends with wheel
bearings close to those ends. Bending loads from the cantilevered
spindle are more than ten times as great and propagate up the fork
leg that is otherwise not loaded in bending from the spindle.
Looking at automobile wheel support, the size and design of axles and
support spindles is done with care, having large transition radii and
solid anchoring in housings and steering knuckles that do not look
like the features visible on the Cannondale struts.
What we need next is this design with a disk brake to make all the
problems work together to enhance failures.
Jobst Brandt
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Date: 16 Jun 2007 07:24:18
From: Ryan Cousineau
Subject: Re: Cannondale Mtn Bike Recall
|
In article <s1n6739i1ehqkvn111291kgj4v0990t24q@4ax.com >,
Fritz <kh6zv9@yahoo.com > wrote:
> On Wed, 13 Jun 2007 13:53:07 GMT, Kristian M Zoerhoff
> <kristian.zoerhoff@gmail.com> wrote:
>
> ><http://www.cpsc.gov/cpscpub/prerel/prhtml07/07211.html>
> >
> >"Cannondale Announces Recall of Mountain Bicycles;
> >Lefty Forks Can Break Unexpectedly"
>
>
> Of course that stupid design would be dangerous.
In fairness, This design has been produced for years and years (a decade
yet?) and this recall covers only 2007 model year forks and a few
2008-designated forks. That suggests the failure was a newly introduced
design or manufacturing flaw, not an inherent failure of the design.
And indeed, this is the first I have heard of anyone having problems
with them being dangerous.
--
Ryan Cousineau rcousine@sfu.ca http://www.wiredcola.com/
"I don't want kids who are thinking about going into mathematics
to think that they have to take drugs to succeed." -Paul Erdos
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Date: 16 Jun 2007 07:24:45
From: Fritz
Subject: Re: Cannondale Mtn Bike Recall
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On Sat, 16 Jun 2007 07:24:18 GMT, Ryan Cousineau <rcousine@sfu.ca >
wrote:
>In article <s1n6739i1ehqkvn111291kgj4v0990t24q@4ax.com>,
> Fritz <kh6zv9@yahoo.com> wrote:
>
>> On Wed, 13 Jun 2007 13:53:07 GMT, Kristian M Zoerhoff
>> <kristian.zoerhoff@gmail.com> wrote:
>>
>> ><http://www.cpsc.gov/cpscpub/prerel/prhtml07/07211.html>
>> >
>> >"Cannondale Announces Recall of Mountain Bicycles;
>> >Lefty Forks Can Break Unexpectedly"
>>
>>
>> Of course that stupid design would be dangerous.
>
>In fairness, This design has been produced for years and years (a decade
>yet?) and this recall covers only 2007 model year forks and a few
>2008-designated forks. That suggests the failure was a newly introduced
>design or manufacturing flaw, not an inherent failure of the design.
>
>And indeed, this is the first I have heard of anyone having problems
>with them being dangerous.
I wouldn't want to be barreling down hill with one of those suckers
holding my front wheel on.
Another case of taking a reliable design and turning it into a goofy
questionable design.
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Date: 13 Jun 2007 15:59:43
From: Ron Hardin
Subject: Re: Cannondale Mtn Bike Recall
|
Kristian M Zoerhoff wrote:
>
> <http://www.cpsc.gov/cpscpub/prerel/prhtml07/07211.html>
>
> "Cannondale Announces Recall of Mountain Bicycles;
> Lefty Forks Can Break Unexpectedly"
``Consumer Contact: Owners of these bicycles may call Cannondale’s toll
free number: 800- BIKEUSA (245-3872) between 9 a.m. and 5 p.m. ET..''
Interesting fact : 800- USABIKE gets you Huffy.
--
Ron Hardin
rhhardin@mindspring.com
On the internet, nobody knows you're a jerk.
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