verktyg 

DON'T MESS AROUND!

You don't want to become a candidate for the award do you? "Hey watch this"...




Unlike steel, aluminum can only be bent or deformed a small amount before it looses a critical amount of strength and reliability caused by sometimes undetectable cracks and stresses which can lead to unpredictable catastrophic failure!

With 20-40 year old used stems, you may never know what they've been through.

I've never understood why some folks who've spent hundreds to thousands of dollars on a bike and components want to save a few bucks on something so mission critical as the bars and stem???

verktyg HEY WATCH THIS!

thook

his stem's not that old, man. and that cinelli is lightweight stuff. moreover, someone had to go gorilla on that to make those stresses even happen

otoh, is that even a 1A stem? looks like one, but maybe it's only a similar style made of inferior aluminum or process. nitto is quality and what the OP is dealing with isn't that extreme

being conscientious of one's work is good, but let's not get too alarmist

oneclick 

Both of those failures look suspiciously like they started at the stress-raisers - the clamp one is obvious, the second has a smooth clamp area (good) but shows indentations at the chamfer of the bolt hole, likely from a bolt with a serrated shank.

The first would be a design failure, the second design or possibly user.

scarlson 

Additionally, would be curious if either of the failures pictures above caused crashes, and how noticeable the first one was, for how long, before it completely broke.

Watch this? Certainly watch your bike for cracks!! But with some rare exceptions, parts should be innocent until proven faulty beyond a reasonable doubt. Let's be reasonable, here.

I could rant and rave about the litigious american culture breeding mass alarmism and ruining things for everybody, but I'm trying to exercise restraint.

dddd

The pictured Cinelli with the splits at the bolt hole is from the particular bolt that was specified for use with a rather thick reflector bracket!

When people removed the brackets and then tightened up the tapered-and-splined binder nut/bolt, the taper could then blow apart the metal surrounding the hole. This was from the era of new safety regulations, late-1970's and lasting into the eighties before Cinelli got rid of this troublesome bolt interface.

Aluminum does in fact degrade with age when held in tension at any part of it's cross-section. While semi-recent advancements in metallurgy/processing have allowed for the unlikely advent of aluminum spokes on the market, aluminum suffers from susceptibility to "creep yield" failure as prolonged tension eventually pulls this metal apart. Steel alloys on the other hand have no such weakness, at least not at relatively low temperatures below say 600+F or so. The classic failure of radial-laced hub flanges would be a good example of creep yield tensile failure of aluminum at roughly room temperature.

I've reamed out a 25.4mm stem clamp to 26.0mm on a Kalloy-made alloy stem, since it was of thick construction shared by their identical 26.0mm stems.

Very hard to remove aluminum with abrasive stones without quickly clogging the abrasive surfaces, so I wrapped coarse belt-sander paper around a dowel and rotated the stem back and forth as I slid it forcefully along the dowel, adjusting the gap tension as needed (I started with an Allen key wedged into the gap). This method was intended to have a forceful, automatic self-centering action to it, which preserved the alignment and roundness of the bore.


Death-stem-be-gone!

cudak888 

I'm really curious about this one myself. I'm guessing it's a Cinelli 1E - basically a 1A where Cinelli swapped the knurled blind front bolt and rear Allen binder barrel for a front Allen bolt and rear knurled nut.

1A hardware (left / front of the stem - rear / back):


1E hardware - (left / rear of the stem - right / front):


Either way, it just seems like a really bad idea to design an aluminum stem that relies on a press-fit knurled bolt that's going to apply radial pressure around the structure of the stem. Not that there's a bunch of 1A's running around just fine, but given that the 1E's are less talked about and easily confused...makes you wonder.

-Kurt

uprightbent

Gotta revive this older thread, after just using the coin trick to very gently spread a late 70's SR alloy stem. Besides the steel stem in the Rene Herse photo, doesn't Nitto show their spreader tool in many photos being applied to their alloy stems? Almost as an acknowledgment that's it's an okay practice? I know aluminum behaves differently from steel, and maybe the Nitto tool is safer by only spreading a minimal amount for a brief pry, but I don't recall seeing many steel Nitto stems, so I wonder how they'd make a tool known to spread the majority of their own alloy stems, without some type of disclaimer. I should add that I've used the coin method in gentle increments, only turning it bit by bit, just to get the bars over the sleeve, then quickly releasing the tension. I've never felt comfortable doing this but it does seem to be an accepted practice.

merziac

Yep, I have one of their tools and have never found it very useful for the shape and bend of it but it can help sometimes, it seems to be designed to limit the force it can deliver, likely with good reason.

I have several other persuaders of various levels of severity, patience and caution are key as with so many things in the C+V universe.

oneclick 

By staying in business?

Because your parts don't break?

Soody

I've seen several cinelli quill stems overtightened from 26.4 to 26 and crack. Plus the bolts always seem to fail.
I have never seen a nitto stem crack, and the old ones have all been abused every which way.
Nitto do extensive cycles of stress testing on their parts. It's pretty cool if you look at a video of their factory.
I've also never seen the more common Sakae Ringyo ones crack. I don't think the decent stockier quills are prone to break at all.
Periodic inspection, cleaning, careful hand on the wrench, and grease, makes for a safer install of a steering system than most people have.

I'll scrap vintage handlebars with much gouging, which sometimes pains me to do, but that is a real danger.

Soody

If you're gonna scrap everything which is moderately sketchy then you're gonna be scrapping a lot of good rideable bikes than ordinary people enjoy.
Every wheel the brake track is past the wear indicator.
Every fork with a steerer threaded too long.
Every bike with a carbon fork more than 5 years old.
Practically every helmet in existence.
Practically every department store bike.
etc etc etc

I don't consider that reasonable.

With old nice parts (like a nitto quill stem) I like to sensibly relegate them to cheaper, more chill bikes as they get more beat up.
The bike you trust going 80 km/h down a mountain doesn't have to be the same one you pick up fish and chips with.

AdventureManCO 

What I really wanna know is...did the OP bin his Nitto, or not? Kinda on the edge of my seat!

Road Fan

I've used gentle levering to remove a number of stems from bars. The nature of the lever, be it a flat screwdriver, not-too-thick 10 mm open-end, Nitto-like lever, or a coin used to press open with a bolt in the relevant treading, but limit your pressure to open the clamp only as is necessary for a slightly slippy disengagement. Over-squeezing any kind of lever, just like over-torquing a torque wrench just to see "now what can this baby do?" (I call that a Tim Taylor) can create damage which did not previously exist.