albrt 

I have modified a couple of these stems on non-collectible older bikes by cutting off the tabs at an angle and replacing the plug with an angled wedge. I am not an engineer, but it seems like this should eliminate the problem of the stress being concentrated in one place at the top of the tabs. Any thoughts on this hack? I suppose it would not fix the problem of a stem being too small or too light for the job.

79pmooney

You have heard me say this before - I consider the chain of components from front tire at the road to the handlebars and brake levers life and death. Failures anywhere on that path can be catastrophic. I got to see this when my fork failed at the steerer'crown junction. Known to be a weak point on those forks but no one had heard of actual injury. Well, it cost me 5 days of my life (coma), 7 years before I could return to my alma mater and re-take my engineering classes, my lifelong dream and separated my life into two, before and after.

I haven't heard of AVA's breaking but then I took mine off my UO-8 and put on a TT or Cinelli. I did associate those stems with injury and suffered one I will never forget but it was hardly life altering. I impacted my sternum hard on that bolt as a early teen. (Hit a rock I didn't see coming down a fast descent into a free-for-all intersection. Hands lightly on the bars and brakes. Hands got knocked off, I slammed that stem and flew through the intersection with my hands down by the hub. Pretty sure I woke up a few motorists. No stems with protruding bolt heads have graced one of my bikes since.

steelbikeguy

Yeah, these stems are not the greatest. The failure that I've seen mentioned the most is the cracks the start at the slots in the quill.
A quick shot of a slot in an AVA stem that I owned briefly...



When I owned this AVA stem, the thing that caught my attention was the remarkably lack of stiffness in the extension. I attributed this to the fact that the extension is hollow, leaving not a lot of aluminum to handle the bending and torsional loads. This hollow extension also indicated that the stem was cast instead of being forged, resulting in less strength in the aluminum that was there. I wasn't ready to trust that, so it went to someone who liked this bit of French engineering.



In all fairness, it wasn't just AVA that used these square ended slots in their quill. The GB stem on my Raleigh International has them too. One suggested fix is to get rid of the square corners of the slot, since they act as stress risers (i.e. places for the stress to concentrate and promote the formation of cracks). Changing the shape from square to round is one way to deal with this. Here's a shot of my GB stem in its current state.



Steve in Peoria

noobinsf 

I had a broken Ava on a Puch that came to me as a freebie. That was all the evidence I needed. Admittedly, I’m not a purist, and it’s important to me that I’m not worrying about safety or basic function when I ride. The crack started at the slit and had progressed to about half the circumference, so I’m glad I never rode with it.

Sluggo

As steelbikeguy notes,GB stems had the same design flaw. I had a (Schwinn Approved) GB that developed a crack on the corner of the square slot. My death was not imminent, but I did NOT use it for long after I noticed the crack.

79pmooney

Funny, bent a GB bar on the same UO-8 I bruised my sternum on. In fact, the bar that replaced the steel one when I went to a better stem. The GB had many previous miles. I did it in when I dropped the UO-8 wheel into a bottomless March pothole with a car beside me. (Winter training in New England.) Wheel made it through just fine - well perhaps not the same shape but it was roughly a polyhedron or something to start; my winter sewup wheels not being round in any sense after January. So I rode on. 10 miles later I happened to look down and I had a 30 degree bend at the edge of the re-enforcing sleeve!

I liked the old soft metal HBs. Much more likely to bend than break.

albrt 

Here is a picture of a doctored death stem.


It seems to me even if the tip somehow broke off at the location of the old failure point, the stem would still be wedged firmly in the tube. Again, that does not protect you from other potential failures due to the stem being too small, too light, not inserted far enough, etc.

RandolphCarter

I had a early 70s UO-8 with an AVA stem. It broke completely while I was in my driveway and just starting out on a ride.

I ended up in the rhododendrons. Easily could've been much worse.

Cycling is dangerous enough without adding extra risk. Especially unnecessary risk.

Gashouse

Hello,
Attached is a photo of the crack partially around the circumference of
an AVA stem found on a 1972 Peugeot PX-10 I acquired. The too-shallow
depth of insertion can be seen just above the slot. The stem is also slightly
bent to the side. I suspect the bike fell over with the rider aboard.

Cracked at top of slot and half-way around. Bent, too.

AVA stem removed before anyone got hurt.

Chombi1 

I think AVA stems are lighter than most other brands because the tube walls are thinner.
The thinner tube wall results in the propensity to crack at the slits machined for the quill wedge.
Chances of cracking can be lessened (but not guarateed) if the top of the slit is drilled out with a round hole diameter wider than the quill slit) that will eliminate the stress risers at the end/corners of the quill slits.

SurferRosa

The first thing that came into my head was "this post didn't age well." Then again, and knowing your sense of humor, I think it's perfect.

rootboy, you are still loved.

stardognine

Exactly why I use a "heavy" chrome handlebar. I've never broken any, but pretty much always had a mild fear of it. 🤪

Bad Lag

I had one break on me. I made a right turn onto a large, high speed avenue and was accelerating hard. When it snapped, I almost fell. I was moving ~15 mph, alongside traffic and had no means of steering. I was, LITERALLY, holding the bars in my hands separate from the bike. I had the presence of mind to stuff it back into the steering tube and regain enough control to stop the bike.

All this happened in less time than it took you to read this.

It broke slightly below the level of the steering tube.

The stem looked something like this and like the one shown above by Gashouse.

oneclick 

Pic below, left-right, top row first:
Peugeot (red stripe one), but I have seen this with a Mercier badge, don't know the real mfr
Atax
GB
Cinelli
Pivo
Ava
Raleigh but I think this is also a re-brand, is a nice strong stem
Cinelli
Pivo

They all except the Raleigh (which arrived with a nicley rounded top) have had the top-of-the-slot mod, even the useless 1R.



Here are all the hollow ones. Some are closed-back.

A previous poster was worried that the loss of material in the centre of the stem would compromise bending and torsional rigidity/strength; though this is true the best distribution of material for such stresses (absent a non-random distribution) is a tube, and the larger the diameter the better (with a practical limit on the order of 25:1 dia/wall ratio). As the walls of the stem's extension are much thicker, and usually shorter, and often larger in diameter than the walls of the tube I suspect that is not even a sensible (rigidity) factor. The absence of reports of stems - even drilled-for-bake-cable ones - argues against a strength issue.

However, there is also the stress from the stem-bolt, and an open back is much weaker here than a closed one; they are to be preferred:



Some slots are oriented fore-and-aft, some athwart. Here are the Cinell's. In re the 1R (right) they are also a known crack-candidate - right across the front of the clamp through he centre of the badge-hole, the crack starts from one (any) of those grooves on the inside surface of the clamp:

ShannonM

Anyone who's ever had any sort of front end separation will advise not rolling those dice.

Even if you don't die, or spend a week in a coma and 7 years in recovery, it's gonna really, really, REALLY suck. And once the front end comes apart, it's no longer up to you how bad it's gonna suck.

--Shannon

JesseABN

I just purchased an early-eighties Peugeot with the CTA stem. Yesterday the seller took it to a bike shop for shipping and when they went to remove the bars they broke the stem clean off. After reading this thread and looking at the pics from the seller, I think the stem was way too high and obviously something caused the fracture to start. Then the bike shop guy finished it off when he was trying to remove the stuck CTA stem. More to follow when I receive the bike!

79pmooney

I think the stem on my '69 Peugeot UO-8 was an AVA. And no, I didn't die but I did try to punch a hole in my sternum with that quill bolt. (Came into the free-for-all intersection off a fast descent, hands over the hoods ready to brake. While I was surveying traffic, hit a stone that knocked my hands off the bars. Slammed that sternum and rode through the intersection with my hands down by the QR. No traffic, so no big deal - except that hurt! (The things we do when we're 14.)

bikemig 

On bikes I rebuild to ride, I replace the bar and stem with new Nitto stuff.

JesseABN

Once I get the bike and measure the tube, which I’m thinking will be 22.0 mm, can you point me in the best direction? Going back original is probably not my best bet since I want to actually ride the bike.

bikemig 

Nitto stems sometimes just drop right in on French bikes. Posters have had good luck with Origin 8 stems fitting on French bikes as well. If the Nitto stem doesn't fit, check to see if it fits the steerer column. If it does, then the issue is the lock nut and you need to take some material out of it. Last you can carefully sand off a bit of material from the stem to get it to fit.

There are a few threads on this, https://www.bikeforums.net/classic-vintage/1245444-who-sands-nitto-pearl-their-french-steerer.html

https://www.bikeforums.net/classic-vintage/1029984-vo-stems-fit-into-french-steerers.html

SurferRosa

Note to self: ask seller to free stem and seatpost, pre-purchase.

JesseABN

Here’s an update on the bike I got off eBay. The pictures from the seller show the stem very high then broken when packaged at the bike shop. I didn’t get the broken part, which I’m glad that was removed from the forks. Looks like what was previously described. The crack must have started at the hole at the top of the expansion slot. Lesson learned: if you have one of these vintage ATAX stems, periodically pull it out and check for cracks! From what I’ve gathered, including the date on this stem 12 80, this bike is a 1981 PXN10.

MooneyBloke

The Cinelli XAs were similar. I have a 1-R which while not failing on the road has troubling signs when examined with a loop. I forget if that one also had the plastic insert like the XA. Nice thin bit of Al, a small radius hole for the plastic logo insert, and the grip grooves on the inside made for a real nice stress riser. I actually had one crack across the front when I was starting towards home. Happily, I didn't crash, but these days, I run CroMo tig stems. They just seem a lot more solid than the stems of old.

I had a TTT Status on the Mooney (#716) that got lost to a bad driver, and while that stem didn't break on me, it seems to flex like overcooked spaghetti every time I stood up to honk when climbing, and that just doesn't inspire confidence. I like the TTT ergo bars, but that stem left me unhappy. So my Mooneys have Salsas (don't know if Shafer or QBP era) with the stickers removed, and my townie has an old Tioga T-Bone Prestige. I believe in these more than the stems I've had throughout the past.

cudak888 

I've found:

• AVAs and Pivos cracked at the expander wedge where they're not relieved,
• A gold-anodized Phillipe-ATAX stem crack at the binder bolt,
• A 1990's-era 3TTT stem cracked at the front of the clamp due to overtightening the 26.0 stem on a 25.0 bar with no shim,
• A Cinelli 1E cracked from the poor fit of the factory knurled nut spreading the aluminum hole where it fits,
• Pretty sure I've come across at least one of those aforementioned button-logo Cinelli 1Rs or XAs that cracked on one side of the button hole.

About the only thing I haven't heard of or seen cracking or failing is an SR or GB stem (also used by Schwinn), come to think of it - and I'm sure it's happened and I simply haven't heard of it yet.

-Kurt

Lotussiddharta

Hello there, I just recently got an AVA stem for my Raleigh grandprix mixte, the stem insertion requires a 21.1; when I got the new AVA stem that was supposedly a 21.0.. it did not fit the insertion, but I needed a new stem badly since I got the Raleigh with what could be a retro/vintage mountainbike stem on and was not very pleasing to look at..

We decided to use a grinder to make the stem slimmer to fit in the insertion, it worked and it seems that the stem is in pretty good condition to snap, besides I am very cautious and a gentle rider since most of my bikes are vintage..

I am still to find out how strong the AVA stems are even when it has been modified

Here are some photos of my bike before and after