Cheating death..............stem
 

I finally got around to cleaning up the 77 P10, while wiping down the stem I noticed a hairline crack in the clamping area. Guess all that talk about 70s Atax stems being "death stems" wasn't all talk. I was looking at the top of the expansion slot and didn't see the crack until I set it on the work bench. Crisis averted, this will probably be a paper weight or something. Glad I took the time to check it out.

http://i287.photobucket.com/albums/l...pskcruoyrj.jpg

Puts on cranky old man voice:
In my day, even the death stems had a 38 year service life. So don't talk to me about craftsmanship, kid!

But can you do the cranky old man voice with a French accent? Lol

The Headbadge: Death Stems Demystified: AVA and ATAX

covers Atax as well. But yes, I think I will take a closer look at everything that comes into the workshop just in case.

...a lot of the old aluminum alloy stuff was considerably less sophisticated in manufacturing technique (forged v. cast, heat treated v not, etc.) and was never designed to last forever anyway. Here is some stuff I saved as class examples for the co-op (off a PX-10 IIRC):

http://bikeforums.net/attachment.php...hmentid=448756http://bikeforums.net/attachment.php...hmentid=448757http://bikeforums.net/attachment.php...hmentid=448758

Damn straight! The only reason I changed the Atax out of my '71 PX-10 was because the bike's too damn small and I needed a longer stem to compensate. Original owner had 2 sets of bars break, but that Atax held strong for 87,000 miles (I kid you not, it's documented).

3alarmer,

No matter what make of bike the stem was on, it isn't French... It's an early 70s Japanese made Arai cast aluminum stem.

French stems were 21.9mm (22mm nominal). Most other stems from that era had 22.2mm quills. Some French bikes came with Japanese bars and stems on their lower priced models (plus some French steerers were sloppy enough to take and undersized 22.2mm stem).

The bars look like they have a randonneur bend and they wouldn't have been standard on a PX-10 either. They probably came with the stem when someone changed it out to get a shorter reach.

Easy way to tell the difference, early French bars are 25mm at the center. Japanese bars were 25.4mm - 1" diameter.

PX-10s from the 60s and 70s came with longer than normal length stems for the frame size because they were racing models. My all original 1967 54cm PX-10 had a 100mm AVA stem.

Barn bike PX-10 as purchased:

http://bikeforums.net/attachment.php...hmentid=448783 http://bikeforums.net/attachment.php...hmentid=448785

Early 60s PX-10 - not my bike, eBay picture:

http://bikeforums.net/attachment.php...hmentid=448784


"was never designed to last forever anyway."

The life expectancy of a "10 speed bike" back then was about 5 years with moderate (or less) use... :eek:

The US Bike Boom was a 3-4 year FAD and no one considered that these bikes would be collector's items 40-45 years on. Also in the US we were probably at the peak of the throw away culture.

Most of the bikes from that era have been reincarnated at least several times by now! :lol:

Your 1970s bike:

http://bikeforums.net/attachment.php...hmentid=448782


Check out this post for more info on death stems:

http://www.bikeforums.net/classic-vi...l#post17767500

Please see my additional posts in this thread...

verktyg :50:

Chas.

Another Chas. Novella - Treatise on "Tige de la mort" (Death Stems)
 

Antieverything,

Good eye.

BTW, that's an ATAX pressure cast aluminum stem (euphemistically called "melt forged" by the Japanese in "Jinglish"). ATAX was part of Phillipe.


There were millions of cast aluminum bike stems produced from the 1930s up to the present. They were made by dozens of companies. For example from the C&V era alone:

France
ATAX
AVA
BELL
BELLERI
BF
CTA
GUID
MILREMO - Made by Phillipe and others
PHILLIPE
PIVO
And others

Italy
3TTT
AMBROSIO (3TTT)
CARNIELLI
FB
ITM
And others

UK
GB and others

Japan
ARAI
NITTO
SAKAE RINGYO - SR
Many other brands

velobase link to stems:

VeloBase.com - Component Listing

The point is that most of them have performed satisfactorily over the years.

The problem was that during the US Bike Boom of the early 70s, the demand was so high for "10 Speed Racing Bikes" that European component makers couldn't keep up...

Consequently many poorly cast aluminum stems that should have been thrown back into the melting pot ended up on new bikes. From my experience it was these poorly made cast stems from the early 70s that where the one that most frequently failed.

Unfortunately Sheldon Brown RIP, chose the cast AVA stems to tar with the "Tige de la mort" death stem label. AVA stems were far from the worst offenders. In my experience, I found that the French made Pivo cast aluminum stems were poorest made...

Here's a BAD example of a Pivo stem that should have never made it out of the foundry:

http://bikeforums.net/attachment.php...hmentid=448800

The casting shrinkage defects in the quill were probably caused by the casting cooling too quickly leaving voids in the surface. The quill should have measured 21.9mm (22mm nominal size). In places this stem measures ~21mm! It was only 21.9mm at the bottom! :eek:

Something else that happens, when the temperature of the molten aluminum is not hot enough it results in large size grains or crystals forming when the casting cools. These large crystals are not as strong as finer grain size crystals and crack more easily along the crystal planes. One advantage of forging is that crystal grains sizes are much smaller resulting in denser, stronger products.

Fine grains on right - coarse grains on left.

http://bikeforums.net/attachment.php...hmentid=448801

This early 70s Milremo stem made by Belleri shows the coarse grain structure where the stem broke off (while I was riding): :eek:

http://bikeforums.net/attachment.php...hmentid=448802 http://bikeforums.net/attachment.php...hmentid=448809

I wrote this post back in 2008 (see Verktyg messages):

gitaneusa.com :: View topic - death stem?

A recent BF post:

http://www.bikeforums.net/classic-vi...l#post17767500

Columbo moment:

One other thing... (or more) ;)

Most of the poor quality stems were sand cast (vs. die cast). The sand cores could shift while the molten aluminum was being poured resulting in voids and thin casting walls in places which weakened the stems. Also the wall thicknesses of the quills were too thin to begin with.

The most common area where these stems failed was at top of the expander split or splits at the insertion end of the quills. The sharp corners of the splits created "stress risers" which generated cracks.

An easy solution the lessen the possibility of crack generation is to drill or file a round hole at the top of the split. A Dremel tool with a small burr works great. You can use this trick on any stem.

http://bikeforums.net/attachment.php...hmentid=448795

Another failure point is the bar clamping area. Using a bar that too small of a diameter is the most frequent cause. Unlike steel, the bar clamp on an aluminum stem can only be compressed a small amount. Cast aluminum stems can be even less compressible.

Don't try this at home kids!

Here's a Cinelli stem for a 26.4mm bar that I used with a 25mm French bar for years. I put this combo together back about 1975 before "we" knew better. A few years ago I wanted to switch to a wider bar. When I tried to spread the bars clamp the front end popped off with a musical ping sound! :cry:

http://bikeforums.net/attachment.php...hmentid=448796 http://bikeforums.net/attachment.php...hmentid=448803

Notice the fine grain structure in this Cinelli forging.

Here's a 3TTT stem someone gave me. When I went to use it I discovered the cracks from being used with an undersized bars - should be 26mm don't use with a 25.4mm or 25mm bar!!!

http://bikeforums.net/attachment.php...hmentid=448797 http://bikeforums.net/attachment.php...hmentid=448798 http://bikeforums.net/attachment.php...hmentid=448799

It could also be the result of a flaw in the metal...

The forged Cinelli and 3TTT stems were top quality - much stronger than most cast aluminum stems!

So, it never hurts to inspect your bars and stem periodically. Any squeaking, creaking or loose feel should be carefully inspected!

verktyg :50:

Chas.

Didn't they make SHIMS back in the stone age, Verktyg?

;)

Yikes! Not all aluminum is created equal. Going to check my stem now...

Thank you very much for this very insightful post which is among the best discussions of this problem I have seen. It must have taken you a considerable amount of time to put it together.

I do have a couple of points:

1) Drilling a stress relief hole may not provide provide insurance against failure if the failure already started before the hole was drilled. You may be leaving behind micro-fractures that you can not see. Also, I do not see how the interior edge can be deburred. It is still a wise precaution, but does not eliminate the need for frequent inspection.
2) The nature of aluminum is such that with repetitive stress cycles it will ultimately fail, so even if there are no cracks now, there will be.
There are a few sites now that have shown testing of modern stems with cyclical loads and they too will ultimately fail. It is the nature of the metal.
3) Nobody talks much about seatpost failure, but I think the same "rules" apply.

Thanks again for your post.

r