Broken stem, the sequel?

[Rick Warner]

Werehatrack <[email protected]> wrote in message news:<[email protected]>...

> Perhaps the problem is that there is no two-bolt design
> that is as robust as one with four. Since three different
> manufacturers have had the same kind of problem, I'd say
> that there's enough of a pattern to say it's the design
> itself, not its execution. One would be a random error;
> two a concidence. Three is prudently regarded as a pattern
> until proven otherwise.

No. The problem is in execution, not design. Go back to the
CPSC page on the recall of the Trek/Icon stem; the recall
was not all Icon stems of that genre, but those with the
narrow faceplate. The wider faceplate model was a bit
beefier and was never recalled. The 3T recall is of the Zepp
XL, only, and did not include the Forgie or The Stem both of
which are two bolt stems but are a bit more robust in the
faceplate area. The two bolt stems work, but need to be
beefy enough to handle the job. The recalls are on the more
gracile designs without the 'beef'.

- rick

 

[Derk]

Chris Zacho The Wheelman wrote:

> BTW, I decided against the Cinelli stem. I got a Richey
> WCS instead. Mounted in an "upwards" position, it too
> places the rider's weight onto the stem body, rather
> than forcing the cap to support everything. And it has
> four bolts.
In a TOUR magazine test, in spite of the 4 bolts, the
Ritchey WCS was not recommended. (just like 3TTT
Forgie btw).

Greets, Derk

 

[Dvt]

Chris Zacho The Wheelman wrote:
> Anybody here know a good source for M5 x 0.8 S.S. or Ti
> cap head screws? :-3)

My favorite source is McMaster-Carr
(http://www.mcmaster.com/). Try part number 91292A191 as
a starting point. I always get part(s) the day after I
order them. They must have a huge warehouse and a well-
automated system.

--
Dave dvt at psu dot edu

 

[Benjamin Weiner]

Chris Zacho "The Wheelman <[email protected]> wrote:

> BTW, I decided against the Cinelli stem. I got a Richey
> WCS instead. Mounted in an "upwards" position, it too
> places the rider's weight onto the stem body, rather than
> forcing the cap to support everything. And it has four
> bolts. That is, it's supposed to. They fell out during
> shipment so my LBS gave it to me for $35 U.S.

> I got some cap head screws at Lowe's that fit for now.
> Anybody here know a good source for M5 x 0.8 S.S. or Ti
> cap head screws? :-3)

If you are truly worried about your stem or bolts breaking
and bars falling off, why in hell are you thinking about
using titanium stem bolts?

Argh.

High grade steel or stainless steel sounds like a good
choice. Maybe Ritchey will tell you what the spec of the
original bolts was.

 

[Derk]

Hi Chris,

Chris Zacho The Wheelman wrote:

> any reference condemning this stem, I'd appreciate it.
TOUR july 2003

They say the max. torque specifications are not OK. Only 4
stem/bar combinations got their OK: the
Tune/Schmolke,Cinelli, Deda and Syntace.

The Ritchey didn't survive a dynamic test, during which 2
WCS broke after
50.000 cycles of the 200.000 that some other brands
survived.

Greets, Derk

 

[BaCardi]

Originally posted by Derk
Hi Chris,

Chris Zacho The Wheelman wrote:

> any reference condemning this stem, I'd appreciate it.
TOUR july 2003

They say the max. torque specifications are not OK. Only 4
stem/bar combinations got their OK: the
Tune/Schmolke,Cinelli, Deda and Syntace.

The Ritchey didn't survive a dynamic test, during which 2
WCS broke after
50.000 cycles of the 200.000 that some other brands
survived.

Greets, Derk

Where are these tests? I tried looking back for a link. Got one?

 

[carlfogel]

Originally posted by BaCardi
Where are these tests? I tried looking back for a link. Got one?

Dear Bacardi, Derk, and Chris,

I think that this is a different test, but that
it covers some of the stems in question:

http://www.biketechreview.com/stems/stems.htm

Good luck,

Carl Fogel

 

[Benjamin Weiner]

Chris Zacho "The Wheelman <[email protected]> wrote:

> I was wondering if I should spell out Stainless Steel
> instead of just abbreviating it "S.S.". LOL! Now, tell me
> why Ti would break. Isn't there another thread on this
> board stating how great titanium is in regards to strength
> and fatigue resistance?

I knew what you meant by "S.S." High grade stainless steel
bolts are quite strong and a good choice for Jesus-nut
bicycle applications. Andrew Muzi alredy covered much of the
rest of the argument. There are Ti bolts which are also
strong (I believe
6/4 Ti is over 100 ksi tensile strength and some reasonable
fraction of that in shear). You gotta get the right kind
of Ti, though, as lower grades are much less strong.
Titanium bolts also have a tendency to gall. You pay a
lot of money for a trivial weight reduction and a bolt
which is no more secure than good steel and may have
additional hassles.

In general, my point is: Why worry at length about stem
design as you did, and then follow a decision making process
that leads to using a quite light stem (Ritchey WCS, right?)
with potentially lower-than-spec or weight-weenie bolts?

In the meantime, here's a source for bolt strengths and
graded bolts (I have no personal experience, but they have a
nice chart):

http://www.boltdepot.com/ http://www.boltdepot.com/charts/G-
rade_markings_properties.htm

 

[Derk]

Chris Zacho The Wheelman wrote:

> I was hoping for a link, but you gave the essentials.
There is no online article: you can order most tests by
faxing a special fee number.

> I'll keep an eye on the stem, Was the article testing road
> or ATB stems?
Road only.

I wouldn't worry too much, but wouldn't tighten to the max
specified torque.

Greets, Derk