Bike Gremlin

Qull stems rely on just one bolt to hold the bars in place (attached to the fork - i.e. steering column). If it snaps, you instantly loose control of the bike. Threadless forks have at least two bolts holding the stem to the fork - probability of 2 bolts snapping at the same time is very, very low. I'd stay away from quill stems if at all possible (for 1" standard you can still find threadless forks and headsets, though they are not as common).

Kontact

Well, yeah. You can get a carbon fork with different types of crowns, different steerer materials, threaded or Ahead, tapered, a wide range of rakes, custom rigidity, multiple brake mounts. And they can be made much more compliant and comfortable than steel.

pdoege

I would expect said expert to measure the deflection, yield, and other characteristics of the frame and then compare those vs. a known good frame and then discuss how visually detectable defects in the frame lead to the deltas.

What I actually see is a gentleman performing destructive visual inspections and then noodling about without any numbers or data.

I did find the different layup techniques in the differently aged frames to be interesting. I think it is clear that a process without voids and etc. can deliver a lighter frame. We don't know if the lighter frame with fewer voids and etc. is better than the BMC frame because no measurements were made and no comparisons were performed in the videos that I watched. We do know that at least some carbon fiber parts that work well are not aesthetically pleasing when cut apart.

The BMC frame, with all of its imperfections seems to have done a perfectly fine and safe job of carrying its riders about. I learned that that fairly mediocre carbon frames work really well, and that the aesthetics of disassembled carbon parts has little bearing on their real world performance.

Kontact

No manufacturer releases its failure rate to the public, and not even to dealers. So you are making an assumption that BMC frames are equal to other frames for failure rates, but there is no reason to make that assumption. There is zero data.

It may very well be that the ugliest parts of those frames are in effectively unimportant areas. But why put loose chunks of non-load bearing fiber in an area it isn't needed? Maybe it just makes things easier to lay up, or maybe they shouldn't be hanging in space like that, it is hard to tell.

What isn't so hard to tell is when you cut up a bike that doesn't have any extra junk anywhere. There isn't any question about whether the stuff you see is merely extra or misplaced, because nothing is extra or misplaced.

The BMC internals make the case for a haphazard build process OR unnecessary extra material, neither of which are hallmarks of the highest level of bicycle technology. Which would be okey-dokey in an entry level Giant, but maybe not in an $8000 bike. These are the McClaren's of bikes, not Deng Fu ebay fodder.

chaadster

I’m hoping he does another series about reinventing the wheel for those who don’t know what round is.

As for the aesthetics having little bearing on real world performance, he does concede that while matte white looks great new, it’s hard to keep clean and so *might* not be a great paint finish for a bike. I guess you have to know both how matte paint works and have the contextual understanding that clean is better than dirty in order to make sense of his point.

So, if your point is that his vids aren’t for everyone, yeah, I can see where you’re coming from there.

kbarch

I dunno. He's just a guy who knows a thing or two about carbon fiber and manufacturing; he's not a representative of a standards institute, is he? Besides, if it weren't for the freak show nature of the video - if it were entirely scientific - it probably wouldn't get as many views.

memebag

Lowering QC is identical to increasing a tolerance. Lower QC means more defects. Higher QC means fewer defects. QC level is tolerance for defects.

Lower QC manifests as more defects. It's true you won't know precisely which defects they are, but you know there will be more.

I don't know enPugh about CF manufacturing or this bike to know if that's a random mess or not, or if it matters.

memebag

Are they? Bicycle Blue Book says it was $5,000 new. So maybe the Nissan GTR of bikes, not the McLaren.

chaadster

@Kontact, it’s hopeless...probably a case of Don’t Feed the Trolls.

noodle soup

I'd like to see one of his frames cut up and inspected like this.

Seattle Forrest

I've wrecked exactly the same number of carbon and steel bikes in my lifetime.

Kontact

That's simply not the case. When you use larger tolerances in a machined part, you know exactly the kind of problems you are going to run into, and can come up with assembly methods to counteract them.

You can't counteract decreased QC on the manufacturing level, because you don't have any expectations of where the problems will be. They are random in a way that a too wide or too narrow part are not.

79pmooney

Yeah, sort of. Quill stems have the long bolt to the wedge or cone at the bottom and yes, it is key in preventing the stem from turning or lifting out. But it does not need to be especially tight. It never sees outside loads. And they very rarely fail. The bolt at the handlebars can fail but with traditional stems. the handlebars are still captive and just rotates. By contrast, threadless stems have bolts that require torque wrenches. When a one bolt breaks, frequently the others do too. The stem itself and the handlebar clamp have also been known to break. When these things happens, the only things holding the handlebars to the steerer are the brake and derailleur cables.

One of the aspects of quill stems I love is that I can very safely adjust handlebar height out on the road with just a 6mm allen wrench (and I might need a rock). No torque wrench, no headset adjustment, nothing to go wrong at all besides perhaps crooked handlebars and threadess setups have that same issue. A very wide range of acceptable torques.

And, yes, a quill stem can just break in two. I am sure there are those here who have seen this happen. (In my 50 years, I have never heard of a casting failure on any well designed and executed stem that hadn't seen use way beyond the expected.)

Lastly: "Qull stems rely on just one bolt to hold the bars in place (attached to the fork - i.e. steering column). If it snaps, you instantly loose control of the bike." Funny, in the Mechanics Forum you hear of people who cannot budge their stems after removing the bolt completely. Now, I ride with well greased quills and wedges and I still have to sometimes tap the bolt down to free the wedge. So in reality, even if this lightly loaded bolt does break, there is a very good chance that nothing will happen at all.

Ben

Dean V

I have never been on a ride and decided I needed to change the handlebar height.
I have however wanted to adjust the headset which is much easier on the modern threadless system.

noodle soup

The cables on my bikes are cut to the proper length, an raising my handlebars would require longer housings.

Kontact

You don't need a torque wrench on a threadless, either. Especially with a metal steerer. You can even change the bar height by rearranging spacers or flipping the stem on the road.

It is okay to like old school stuff, but you are manufacturing "issues" to bolster your preferences.

pickettt

They may look significantly better, but I'd never buy a Cannondale based on my experience with their reliability. I've been racing a long time and I've seen a lot of defects. Granted, Cannondale puts out far more bikes than BMC, so as a percentage it probably doesn't sound any alarms, but that doesn't make it any less scary.

Kontact

Many common brands have a wide variety of QC issues, and unless you personally experience them you are unlikely to hear a lot about the issues. It is somewhat open secret among Cervelo dealers that they're easy going warranty policy gets used - a lot. Not because the frames are breaking in half, but because of BBs that are too large or internal cables that don't work right.

In 2014 Cervelo recalled the P5 integrated bar system. I worked on the first failure - the screws were threaded into tubular anchors that pulled right out of the carbon when you leaned on the bars. Even a competent bike mechanic or cabinet maker would know better. The bike industry does not operate like aviation or automobiles - plenty of people designing and building bikes are frankly winging it.

Specialized just issued a recall on basic, lower end carbon fork.

Racing Dan

Im not really going into the debate, but I will just comment that lots of normal bike components does not, Imo, need a lot of QC because they are dimensioned to take a lot of abuse, are built with proven, cheap manufacturing techniques and does not push the weight envelope. Im sure we can find examples of broken quill stem bolts, but from my experience, with normal commuter stuff, they just dont break. Race bike carbon frames on the other hand are tricky to manufacture and does indeed push weight envelope. That, Imo, requires much more vigilant QC and very conservative rejection criteria. BMC however seem to disagree with me on that point and that is why I would never consider a BMC, based on the video in #1.

Bob Ross

Wait, wasn't the whole point of their oversized BB area to increase stiffness & durability?!?!

chainwhip

My $0.02:

There is a saying in manufacturing: "You can't inspect quality in"(meaning 'into the product').
Very obvious, once stated, but not really intuitive.

Looked at from 1000' up, quality control and manufacturing processes are both necessary steps to achieve the targeted goal(s).

There is a mind-set that insists on their separation.

The parts of the thread that haven't been a pissing contest have been quite enjoyable.
Sorry for the O/T musings.

Kontact

Large as in "out of spec".

Kontact

I agree, to an extent. There are fewer ways for an extruded rim to go wrong without being so obviously wrong that it rejects itself. Some processes are their own QC.

Vacuum bagged monocoque construction has far too many places for things to go wrong. Mandrel wound tube with die formed carbon lugs has very few.

ThermionicScott 

If one person defines "quality" as

and another uses less-flowery language like "low failure rate", why would you be surprised that a thread will go on for pages with no consensus?

chaadster

I did not, and do not, define quality as artistry and mastery.

The thread has gone on for pages without consensus because people do not have good comprehension skills.