This talk of 'death stems' brings back a past [painful] memory, I think it was around November 1970, riding back from a 'circuit training gym class' in Pontefract I had the misfortune to have a stem break clean in two!!............. I had just descended the hill past the castle, so was going at a fair rate when I can only imagine I hit a nasty pothole [it was dark and lights in them days were not very good] anyway, I lost control and crashed into a street light!.........I picked myself up, and checking my bike [isn't this the first thing any cyclist does!] I realised my GB spearpoint stem had broken off just before the handlebars! also my front wheel was bent as a 9 bob note, so feeling a bit concussed I actually crossed over the road and proceeded to walk back towards Pontefract for about half a mile before I realised I was going the wrong way, I had thought in the crash I had swerved accross the road.
Next morning I had a huge bump on my forehead and was sent home from work! [just realised that the very same stem is the one that's on my Woodrup [1st ever 25] in my photo on flickr]
Anyone else ever had a GB stem break?
Cheers
Kevin Sayles
Bridgwater. Somerset UK
> Peter,
>
> Good point about searching the archived, but, but....
>
> I'm not trying to defend the so called cast aluminum "death stems". I'm
> merely providing some technical background that may help some make an
> educated decision about using a cast aluminum stem.
>
> Many of the posts in the archives are about personal experiences, hearsay,
> urban myth and so on. Very few that I've read contain sufficient technical
> details to build a case for or against cast aluminum stems. Many comments
> claim that the stems broke at the clamps. That's not been my experience at
> all.
>
> Back in the 70s I had 3 cast aluminum stems fail on me while riding. I
> worked at/managed a bike shop for 5 years. Two of the stems broke while
> test riding customers bikes. They were the cheap Bike Boom cast aluminum
> stems. The third was a Belleri cast aluminum stem on my own bike. It was
> the first generation Belleri model with a recessed hex head expander bolt.
>
> Fortunately I was going slow enough to bring the bikes to a safe stop all
> 3 times. It's a very scary feeling riding down the street holding the bars
> in your hands.
>
> All 3 of these stems failed in the same place, at the top of the expander
> split on the quill. The true "death stem" in the photo in the link below
> shows cracks forming at the top of the split. Also note the poor quality
> of the casting on this stem. Aside from the insertion depth ring, all of
> the other flaws were part of the casting. Note how the quill is bulged at
> the bottom. This is supposed to be a 22mm French stem but in places the
> quill is under 21mm in diameter.
>
> http://www.postimage.org/
>
> The late great Sheldon Brown (RIP) did both a service and a disservice to
> cyclists in his warnings about AVA "death stems".
>
> The disservice is that it can give users of other makes of cast stems a
> false sense of security because they have a different make stem. People
> with a cast aluminum stem should be aware of the possible safety hazards
> with any these style parts not just AVA stems.
>
> During the Bike Boom of 71 to 74 bike makers used what ever components
> they could get. We sold Gitanes plus a myriad of other French Bike Boom
> bikes. Gitanes usually had Pivo Stems. Peugeots (the competition) on the
> other used mostly AVA stems. I've seen far more poor quality Pivo stems
> than any other make.
>
> Cast Aluminum stems have been used for over 50 years. They should not all
> be tarred with the "death stem" reputation.
>
> Here's a partial list of French cast aluminum stem brands from the Bike
> Boom era. It's not complete and some stem makers used more than one brand
> name. Also there were private label stems like Milremo.
>
> ATAX
> AVA
> BELLERI
> BF
> CTA
> GUID
> LEPPER?
> MILREMO
> PHILLIPE
> PIVO
> SINTESI
>
> Stems that are not inserted far enough into the steering tube are one
> cause for the cracks forming at the top of the expander splits. The rule
> of thumb is a stem should be inserted at least 2" into the steerer.
>
> But, but, but, you never know if the stem had been ridden for years with
> only an inch of insertion and is already damaged without doing a close
> inspection. Here's an example of what I mean:
>
> http://www.postimage.org/
>
> The other problem related to this is the possibility of expanding the
> quill in the threaded area of the fork. This can cause the threads to
> bulge and eventually crack. I repack the headsets on almost every bike
> that I work on, inspecting both the forks and the stems.
>
> Many newer stems have an angled wedge that pretty much eliminates the
> cracking problem but they can still damage the fork.
>
> Casting quality and the type of aluminum ally used are other important
> issues. Cast aluminum is used in most metal based products from automotive
> to aerospace. There are over 40 different aluminum alloys used for
> casting.
>
> Porosity and microporosity is a major problem with cast aluminum. Some
> porosity is caused by precipitation of hydrogen gas during solidification
> from the molten state. Other porosity problems can be the result of
> impurities in the metal. In any case, porosity can result in cracks an
> metal failure. Many of the early cast aluminum stems used really cheap
> casting methods. Modern cast aluminum parts are made pressurized casting
> equipment which reduces the amount of porosity in the parts.
>
> Forged aluminum stems tend to be much stronger that most cast stems
> because the metal is much denser. Forge melting is a marketing term for
> pressure cast parts.
>
> Advice for using cast aluminum stems:
>
> 1. Inspect the stem carefully. Look for any signs of cracks or porosity.
> DON'T use any stem that doesn't look good!
>
> 2. Drill a small hole in the quill at the top of the expansion split or
> splits. This will reduce the tendency to crack in that area.
>
> 3. Don't use a bar that's too small or too big to fit the original size
> that the stem was designed to use. French stems usually used 25mm bars and
> 22.2mm quill size stems used 25.4mm (1") bars. Aluminum in general can be
> fairly inflexible, especially so with casting.
>
> 4. Almost ALL of the French aluminum bars from the Bike Boom era should be
> suspect. Any sign of sagging or drooping, get rid of them. I have seen a
> number of catastrophic failures with these bars. For example:
>
> http://www.postimage.org/
>
> Chas. Colerich
> Oakland, CA
>
>
> -----Original Message-----
> From: Peter Brueggeman <4peebee@peterbrueggeman.com>
> To: classicrendezvous@bikelist.org
> Sent: Thu, 2 Apr 2009 7:44 am
> Subject: Re: [CR] death stem? px-10
>
> Regarding Robert Sasher's query about death stems by AVA etc, the Classic
> Rendevous Archives has considerable past discussion on this topic. I
> usually
> check the Archives first to read what has been discussed over the years. I
> frequently find what I need to know there, and don't post a query to the
> CR
> list. My observation has been that typical recurring questions posted to
> CR
> usually will not receive as good a range in responses as the responses
> aggregated in the CR Archives.
>
> Go to http://search.bikelist.org/
>
> Type in the Search String box
>
> death stem
>
> Select "Sort By: Date (newest first)"
>
> Select "List To Search: classicrendevous..."
>
> Click on the Search button
>
> ...........
>
> Peter Brueggeman
>
> La Jolla CA USA
>
> 4peebee(at)peterbrueggeman.com
>
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