[Opus51569]

Kalloy AL-222 quill stem with a 25.4mm clamp, aluminum, single bolt
Dimension road bars with a 26.0mm diameter, aluminum

I got the bars through the stem and into position. Now I'm hearing there's a good chance either the stem or the bars are going to fail and I'm going to die (or at least be gumming my food for a while).

What say you all?

 

[SystemShock]

You like forcing things into holes that are too small, eh?

TWSS.

 

[Opus51569]

You like forcing things into holes that are too small, eh?

TWSS.

Only when I've already paid for it...

 

[mikerp]

Only when I've already paid for it...

and that makes it right thing to do?

 

[SystemShock]

and that makes it right thing to do?

I think he was joking. You are too, right?

 

[tihsepa]

Yes, uou are going to die.

From that? I dunno. Its not right though.

 

[velodog]

Shux, of course you're gonna die. In fact you could possibly die before your stem breaks.

 

[Opus51569]

I think he was joking. You are too, right?

I tend to assume everyone here is joking, until their poasts convince me otherwise.

With the stem and bars, the mismatch wasn't intentional. I had the stem for a while and when I got the bars, I didn't bother to double check the clamp size. That's what I get for assuming, I suppose.

Now that it's done, I'm trying to determine if there's a genuine risk of danger (beyond the "normal" risks associated with riding). FWIW, the bike it's on is a SS conversion that will be used on weekend outings on MUTs and roads.

If there is a danger, do I assume both the stem and bars are now compromised by this unholy alliance and start from scratch?

 

[JCavilia]

If there is a danger, do I assume both the stem and bars are now compromised by this unholy alliance and start from scratch?

I don't know if there's really any danger, but the damage you did, if any, would likely be to the stem, and not the bar. You had to open the clamp wider than intended, which may have stressed the metal, but the extra load on the bar (considering how much it's subjected to with normal torque) seems pretty insignificant.

That stem clamp seems pretty robust. I'd probably just inspect it closely, and if I didn't see any evidence of cracking I'd probably just ride it. But I'm not a metallurgy expert, and they're your teeth.

 

[0.2HP]

“…the damage you did, if any, would likely be to the stem, and not the bar. You had to open the clamp wider than intended, which may have stressed the metal,…. I'd probably just inspect it closely, and if I didn't see any evidence of cracking I'd probably just ride it.”

+1

Apparently this stem is made from forged aluminum, not aluminum alloy. In general forged aluminum will fail progressively, not suddenly. It will start to crack, and the crack will get a little bigger with impact load (like hitting a pot hole or jumping a curb.) If it starts to crack and you keep riding, one day an impact will cause the stem break in 2, suddenly. If you keep an eye on it and throw it out when you see a crack your teeth are save (at least safe if you brush daily and refrain from insulting bigger guys in bars.)

 

[JCavilia]

Apparently this stem is made from forged aluminum, not aluminum alloy.

The distinction you mean is between forged and cast (I think). This part is undoubtedly made of an alloy. though I don't know which one. I don't think any bike parts are made of pure aluminum -- it wouldn't be nearly strong enough.

 

[0.2HP]

"This part is undoubtedly made of an alloy."

Let me rephrase. Made from a normal, common aluminum alloy like 6061, that is fairly ductile and can have the clamp pried open and forced to fit around a too large handle bar without cracking. Not made from newer, higher strength 7000 series alloy that is too brittle to be stretched without being seriously damaged. Also higher strength aluminum alloys may be more likely to fail suddenly without a warning crack, than a lower strength alloy.

(Bike parts were and maybe are still made out of pure aluminum and still be strong enough. They would just have to be bigger and heavier than an equal strength aluminum alloy part.)

 

[mikerp]

I'm guessing everything is alloy, you got it to fit and it didn't break.
That being said, there are most likely some point loads and stress from deforming the parts. Will it fail at some point? possibly, it depends on what loads it will see. Not guarantee on how it will fail either.

As to dying, it's inevitable for all of us.

 

[Opus51569]

Thanks everyone for your knowledge. I'll definitely keep an eye on the stem. I think if it were my commuter bike (which sometimes takes a beating) I'd definitely swap it out. The bike it's on is a SS resto-mod that I treat with kid-gloves as it is. I'll be thinking about it each time I get out of the saddle for a while, though.

 

[Tunnelrat81]

I have to disagree with the above information, and suggest that this mis-match has more potential to cause a handlebar failure than a stem failure. I don't think it's uncommon for folks to 'convince' handlebars into stubborn quill stems by spreading them, and I really don't see this in itself as being a significant concern. However, If you are clamping a handlebar with a clamp that was built for a smaller diameter (tighter internal curvature), then it's going to exert unequal pressure on the bar, including point stresses at the sharp edges of the clamp (near the bolt). It's the point stresses, when used over time that would cause me the most fear.

A proper fitting stem/bar combo will distribute the squeezing force consistently around the handlbar without adding any sections of either less or more pressure. It's no different than spoke tension in a wheel. A poorly built wheel will last 'some' time, but can't be trusted to be long-term trouble free because the forces aren't even thoughout. I believe that it's no different with stems and bars. I just bought and installed a new nitto stem to go with my new 26mm bars for this exact reason. Everywhere I looked I found the same advice..."Don't do it!"

-Jeremy

 

[Opus51569]

I came across posts similar to the ones you mention. It makes sense, but with the stem/bar combo I have, the only real issue I had was negotiating the bar bends through the stem. Once I got the top into the stem it was snug, but was able to rotate. The only real difference was that when I tightened the stem, I didn't need to tighten the bolt quite as far to hold the bars securely in place.

I'm not saying your advice is wrong, but in my case it didn't seem like there was enough force involved to distort the bars. But I'm certainly no engineer or metallurgist, I'm just describing the process I went through.

 

[Tunnelrat81]

"Didn't need to tighten the bolt quite as far" is indicative of the points of increased pressure. It's not necessarily going to 'cut into' the handlebar and cause a tearing failure, so expecting to see something clearly off isn't very realistic. My thought would be the aluminum soda can analogy. It holds, and seems fine, right up to the point that something (little) unsettles the structural integrity, and suddenly collapses. It's up to you, of course, but not believing in something doesn't make you immune to damage from it. Best of luck though either way. I hope for your sake that the majority of the advice on this topic is wrong.

-Jeremy

 

[refund!?]

Well, I've used mismatched stem/handlebar combos for a few decades - touring, commuting, racing, etc (Both road & mtb) with no problems, so my comments come from experience.

But, in all of my applications very high quality and expensive stems and handlebars were used (Cinelli, TTT, Salsa, Nitto, etc.). So, the question might be, do you trust Kalloy and Dimension stuff when used in compromised ways?

 

[Opus51569]

Well, I've used mismatched stem/handlebar combos for a few decades - touring, commuting, racing, etc (Both road & mtb) with no problems, so my comments come from experience.

But, in all of my applications very high quality and expensive stems and handlebars were used (Cinelli, TTT, Salsa, Nitto, etc.). So, the question might be, do you trust Kalloy and Dimension stuff when used in compromised ways?

Probably as much as I would have trusted the 30 year old bars and stem that came off the bike.

 

[refund!?]

Probably as much as I would have trusted the 30 year old bars and stem that came off the bike.

Your answer has nothing to with the question. The 30 year old stuff was installed as intended and you replaced them; and the Kalloy & Dimension stem/bar, which are entry level components with limitations, aren't, and you're using them.