[Closed] Do stems ever break?

Strength is only one part, stiffness is more of an issue,

stiffness is more of an issue,

And many of the more gravity oriented stems have shapes that make them look burly but actually have little impact on the stiffness of what is, after all, a very short piece of metal with a clamp at each end.

Because the CNC type stems tend not to be a closed section (i.e. hollow, cylinder etc.) they're actually significantly less stiff for a given weight.

Then of course you've got to worry about the actual clamps that make more of a difference, most of which are pretty similar (I've seen one that arguably will give a stiffer interface to the bars).

But yeah they do break from time to time, like anything. And if they do break while you're riding, it's bad. Like most things, fatigue damage is more likely than just one hard landing type failures.

Oh and

But surely the trail type are strong enough for everyone not doing Red Bull Rampage type stuff…?

Probably, yeah. But the DH type should be even less likely to fail, and it's not like a Patriot is ever going to be the basis for a lightweight bike.

I've seen broken faceplates, never encountered a broken stem though.

fatigue damage is more likely than just one hard landing type failures

I always feel the stem on a rigid mtb will get far more stress in it's life than one on a front suspension bike - people very rarely bottom their fork out with any significant force - it's pretty much the definition of what a suspension fork is designed to prevent.

Rigid forks are permanently subject to both high and low stresses (anything the tyres don't absorb) from both the riders weight going down and any obstacles on the trail coming up (and the two in opposition).

Plus, tbh, most 'red bull' riders will probably be changing kit at least annually as bikes/sponsors change over time - people ride a rigid bike for years and barely think about bars or stem.

I've had a faceplate crack, on a Hope XC stem some years ago, mot likely fatigue.  Hope replaced the faceplate FoC (usual great customer service).

I can imagine faceplates cracking from fatigue due to clamping and removing bars.

I've twisted lots of stems. mainly DH/DJ ones.

so yes strength is an issue.

if strength matters to you go for a decent stem made from 7075 and avoid anything light in 6061

I had a bolt head snap on an ancient Orange (generic XC tube) stem.

I also had a faceplate crack on a, very old, Hope stem earlier this year (thankfully I noticed before the crack went the whole way across the faceplate).

As above Hope replaced the faceplate FoC (despite the fact that the stem was well out of warranty, amazing customer service).

My understanding is that Thomson treat face plates as consumable items.

Thomson also treat seatpost diameter as an estimated size

avoid

I’ve twisted lots of stems. mainly DH/DJ ones.

How?  Crashing?  Or just very big landings?

By being incredible, obvs...

Yes I broke a renthal one where the bolt for the steerer goes through. No idea how as I hadnt crashed and used a torque wrench to fit it. I dd replace it with another renthal and thats been fine

Yes! Club Roost I-beam, bitd, right on weld at the steerer. Faceplate on a RF stem that was consequently found to be part of a recall. Twisted a cheap (uno, tranz x maybe) one in an altercation with a tree.

Never broken 1 personally but did see 1 snap clean in half whilst watching a dh race at Hamsterley a few years ago. The lad was going full belt down a pretty hairy rock garden at the time and I'm not sure if the stem snapped before or after he hit the ground but it does happen, direct mount on dual crown fork as well

PX have one for a tenner bearing the name El Guapo which is labelled 'trail/XC'.  Pretty sure it'll be fine, but it's a tubular design and I started wondering about this vs the chunky CNC type.

Saw a friend snap an old style quill stem on his road bike, fortunately just as he was pulling away from a junction and so going very slowly. The weld which joined the vertical bit that goes into the steer to the horizontal bit just snapped clean through.

.

I've had issues with the bit where one of the bolts on the clamp goes splaying open and not letting the bolt tighten but never snapped one myself.

Anyone remember George Hincapie snapping a stem on a cobbled section of Paris Roubaix a few years ago? I was well impressed with how he handled it

PX have one for a tenner bearing the name El Guapo which is labelled ‘trail/XC’.  Pretty sure it’ll be fine, but it’s a tubular design and I started wondering about this vs the chunky CNC type.

Generally tubular = forged with minimal machining. The chunky looking CNC ones... well machining looks lovely but leaves stress raisers. Thomson stems are supposedly solid and strong etc, but see above re. face plates cracking - in reality they're just made in a way that's bad from a fatigue point of view, and are consequently a bit overweight and not that durable.

So a cheap forged stem should be fine, unless as you say you're hitting big jumps, at which point you might bend it. I got a brand X "enduro" stem that's similar design for about a tenner. No idea if it'll actually be stronger but so far so intact. I don't generally do anything huge though!

Use a torque wrench on the bolts too if you're concerned about the possibility of failure - over-tightening is often not a problem unless you break the bolt or pull out the threads during assembly, but can be bad for fatigue in some cases, and stems are one of those cases. (It's to do with the relative stiffness of the different load paths through the assembly).

I’ve twisted lots of stems. mainly DH/DJ ones.

How?  Crashing?  Or just very big landings?

By getting those tabletops so cranked over that you twist your stem to get that last 5mm of invert

I snapped the quill stem on my Raleigh Grifter XL many years ago. Literally in two. My dad took it to work and welded it back together. It was fine.

I have cracked a hope face plate, which was replaced under warranty.  I have also bent/twisted a stem in a crash.  Think it was an on one stem, but cant guarantee it.  Completely my fault as well.

Aren't forged ones supposed to be stronger than machined due to the grain structure alignment during the forging process and the lack of stress risers from machining..?

Depends

Anyone remember George Hincapie snapping a stem on a cobbled section of Paris Roubaix a few years ago

werent it the fork

Yep. The steerer snapped. They'd swapped the standard for for one from a hybrid iirc as it had more rake and should have been more comfortable...

And I've had broken face plates.

Seen a few stems go too. Particularly cnc'd ones fatiguing.

I reckon you're far more likely to break / damage a stem in a crash ( ie bars collinding with something solid) than in a riding scenario, the kind of forces you'd need to damage a decent stem would probably break your wrists first.

On the start line of the MTB Marathon Hope/peaks a month or so back I noticed a crack in the face plate of my Thomson........... but hey what's the worst that can happen.

Welded stems generally.... run away

Yes I broke a renthal one where the bolt for the steerer goes through. No idea how as I hadnt crashed and used a torque wrench to fit it. I dd replace it with another renthal and thats been fine

Exact same on a riding buddy's renthal stem - discovered on morning of first day of a week's Alps riding. Cue a cautious descent to the nearest bike shop (and a few more bike shops til we eventually found a replacement)

And I've found a cracked face plate on an FSA stem of mine many years ago.