Re: Cannondale Mtn Bike Recall

In article <[email hidden]>,

Quoted message said:

[ This is a repost of the following article:
] [ From: Steve Gravrock <[email hidden]>
] [ Subject: Re: Cannondale Mtn Bike Recall
] [ Newsgroups: rec.bicycles.misc
] [ Message-ID:
<[email hidden]> ]

Fritz said:

Kristian M Zoerhoff said:

<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.

Not to mention cars, trucks and anything else that uses a stub axle. A
friend has one and likes it quite a bit, but says it took some getting
used to in terms of looking down and only seeing one fork leg.

Quoted message said:

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.

I liked the HeadShok design from an aesthetic perspective, but I think
the death knell was that there wasn't enough suspension travel available
to sell them to a market of buyers seeking "extreme" riding experiences.
And maybe it didn't look motocrossy enough to sell.

Quoted message said:

[ This is a repost of the following article: ]
[ From: Steve Gravrock <[email hidden]> ]
[ Subject: Re: Cannondale Mtn Bike Recall ]
[ Newsgroups: rec.bicycles.misc ]
[ Message-ID: <[email hidden]> ]

Fritz said:

Kristian M Zoerhoff said:

<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.

[snip]

Dear Jobst,

No need to guess--insufficient linseed oil on the threads.

Really.

"Reason for the recall"

"Thread sealant may have been incorrectly applied to the Lefty Speed
DLR2 and SL damping cartridge threads. Incorrectly applied thread
sealant can result in the damping cartridge loosening while riding."

http://www.cannondale.com/asset/iu_files/techcenter/2007_lefty_speed_dlr2_and_sl_damper_recall_notice_en.pdf

Cheers,

Carl Fogel

Jobst Brandt said:

[ This is a repost of the following article: ]
[ From: Steve Gravrock <[email hidden]> ]
[ Subject: Re: Cannondale Mtn Bike Recall ]
[ Newsgroups: rec.bicycles.misc ]
[ Message-ID: <[email hidden]> ]

Fritz said:

On Wed, 13 Jun 2007 13:53:07 GMT, Kristian M Zoerhoff
<[email hidden]> wrote:

Quoted message said:

Quoted message said:

<http://www.cpsc.gov/cpscpub/prerel/prhtml07/07211.html>

Quoted message said:

Quoted message said:

"Cannondale Announces Recall of Mountain Bicycles;
Lefty Forks Can Break Unexpectedly"

Quoted message said:

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.

Single-sided support of hubs is the norm on most multi-track vehicles,
and on the rear of modern motorcycles.

--
Tom Sherman - Holstein-Friesland Bovinia
The weather is here, wish you were beautiful

Tim McNamara said:

...
Not to mention cars, trucks and anything else that uses a stub axle. A
friend has one and likes it quite a bit, but says it took some getting
used to in terms of looking down and only seeing one fork leg.

How can it be a fork if it has only one leg?

I always refer to the wheel support on my bikes with single-sided hubs
as a "mono-strut" to avoid this semantic issue.

--
Tom Sherman - Holstein-Friesland Bovinia
The weather is here, wish you were beautiful

Tim McNamara said:

I liked the HeadShok design from an aesthetic perspective, but I think
the death knell was that there wasn't enough suspension travel available
to sell them to a market of buyers seeking "extreme" riding experiences.
And maybe it didn't look motocrossy enough to sell.

[ Disclaimer: In keeping with the finest RBT traditions, this is based
entirely on looking at the parts. I have never rode a Cannondale. ]

In theory, they should be able to get just as much travel as with a
conventional fork. You pretty much need the same clearance either way,
whether it's between wheel and crown or crown and head tube. Maybe they
didn't have enough room for the internals of a longer-travel fork.

The bigger practical issue that I see from the customer's perspective is
that the whole system is proprietary. If you buy a Headshok-equipped
bike you need a Headshok fork, headset, and stem. The Lefty doesn't
seem like it would suffer from that kind of lock-in unless C'dale did
something gratuitously weird with either the steerer or the fork length.

Johnny Sunset said:

Single-sided support of hubs is the norm on most multi-track vehicles,
and on the rear of modern motorcycles.

Make that on the rear of *some* modern motorcycles. The large majority
use double-sided support.

--
Ted Bennett

Ted Bennett said:

Johnny Sunset said:

Single-sided support of hubs is the norm on most multi-track vehicles,
and on the rear of modern motorcycles.

Make that on the rear of *some* modern motorcycles. The large majority
use double-sided support.

Note that I wrote "modern" motorcycles, not "current production"
motorcycles.

Our local manufacturer builds new motorcycles that are anything but
modern (which is what the buyers want).

--
Tom Sherman - Holstein-Friesland Bovinia
The weather is here, wish you were beautiful

Ted Bennett said:

Johnny Sunset said:

Single-sided support of hubs is the norm on most multi-track vehicles,
and on the rear of modern motorcycles.

Make that on the rear of *some* modern motorcycles. The large majority
use double-sided support.

trials bikes maybe, but not current japanese road machines. just go to
a showroom.

In article <[email hidden]>,

jim beam said:

Ted Bennett said:

Johnny Sunset said:

Single-sided support of hubs is the norm on most multi-track vehicles,
and on the rear of modern motorcycles.

Make that on the rear of *some* modern motorcycles. The large majority
use double-sided support.

trials bikes maybe, but not current japanese road machines. just go to
a showroom.

What, did they all change since I checked last?

Nope... Honda makes 7 or 8 sporting models depending on how you count.
One of those (the Honda Interceptor, their V4 supersport-tourer) uses a
single-sided swingarm. I may have missed one, but I believe that none of
their other bikes (tourers, cruisers, off-road) use a single-sided
swingarm.

Ducati uses it on several models, but more or less have admitted that
it's a styling tic.

BMW uses single-sided arms on a great number of models; all of their
shaft-drive bikes, I think.

I may have missed a model somewhere, but I believe that Yamaha, Suzuki,
and Kawasaki offer zero single-sided swingarm models among them.

Single-sided swingarms are a viable design; I think Honda started using
it on the RC30 (or the endurance versions of one of those bikes) to
speed rear-wheel changes in endurance races. Either endurance racing
became less important, or other technologies made wheel changes
acceptably fast with a double-sided swingarm.

All things being equal, the single-sided designs are usually a bit
heavier.

Oh, and for the person who was looking for a single-sided front-end on a
bike, aside from the aforementioned Vespas, there's also the now-defunct
Yamaha GTS 1000 model, which used some suspension ideas from James
Parker:

http://www.burningart.com/meico/moto/parker/index.html

Amusingly, the bike had a double-sided rear swingarm. The single-sided
front end was in aid of its rather fancy hub-steering setup. BMW uses a
conceptually similar front end on its Telelever bikes, but the result
looks largely like a conventional fork.

In case you're wondering why, it was an attempt to prevent the
suspension from being affected (either by fork dive or by
stiction-inducing fork flex) by braking.

Here's an article by my friend Gen Kanai on the subject of alternative
suspension designs:

http://www.vf750fd.com/blurbs/suspension.html

--
Ryan Cousineau [email hidden] 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

Not really. My 98 C'dale has a reducer at the bottom of the head tube
and can use ANY 1-1/8 fork

Steve Gravrock said:

Tim McNamara said:

I liked the HeadShok design from an aesthetic perspective, but I think
the death knell was that there wasn't enough suspension travel available
The bigger practical issue that I see from the customer's perspective is

that the whole system is proprietary. If you buy a Headshok-equipped
bike you need a Headshok fork, headset, and stem. The Lefty doesn't
seem like it would suffer from that kind of lock-in unless C'dale did
something gratuitously weird with either the steerer or the fork length.