Dave Mayer

Hmmm. I've looked at the video a dozen times and cannot see evidence that the root cause of the crash was that DeGent had hit something.

I've hit many many objects while riding tubulars, including fist-sized objects that destroys the rim and flattens the tire in one revolution. Unlike clinchers: no drama. The tire stays put tight on the rim and you coast to a controlled stop. Or if you have less than a mile to the finish, and the rim is not too destroyed, you ride it out.

Unlike that of the the tire and rim vendors, here is an analysis that I trust::

VegasJen

I actually watched that whole video (and understood quite a bit of it), and he makes a lot of sense. I would be interested to hear from others with an engineering background that want's to counter the points he made, but he backed up his opinion with solid engineering.

phrantic09

When he goes down you can other debris in the road. Based on the pic of the rim, it’s clear he smacked something pretty hard, but folks ITT continue to ignore it to push their own narrative.

Mojo31

I can’t let my wife read this. She has the only bike with hookless rims. 😜

DaveSSS 

Regarding the Hambini video, of course the stress formulas are correct, but his flexing of the rim flanges is lame. They're not all the same. Hooks can be present, but minimal and relatively worthless. Those favoring hooks are quick to assume that their tires will stay on with no information about the design of the hook. My BTLOS hookless 25mm IW rims are 31mm wide, so the flanges are 3mm thick and quite sturdy. Some hooked wheels have about the same thickness at the hook, but the recess below it is significantly thinner. It has to be, or there would be no hook. BTLOS makes hooked rims with the same 31 outside width, but adds material to the inside, so the internal width is only 22mm. A Campy Bora is only 28.4 mm on the outside and 23mm internal width.

Hambini should explain why auto and motorcycle rims are hookless, but work well since we also have run flat tires. Of course the answer is that the tires have very strong beads and stiff sidewalls. Buyers wouldn't want their bike tires made that way.

Hambini also dismissed the lower pressure suggestions for hookless as being too low. I've been following the Zipp pressure calculator suggestions for over 2 years now. I've got no way to measure rolling resistance, but the ride is certainly much better on chip sealed roads. If you like, you can always add 5-10 psi and convince yourself that you're now faster.

​​​​​​I got my mechanical engineering degree in 1981, at age 28.

79pmooney

Minor engineering point - bicycle wheels, even with very light rims, are impressively strong against in-plane impact - until the rim itself is damaged. More tire pressure = less chance of impact damage to that rim. Did De Gent's rim fail (apparently in-plane judging by the symmetry of the failure) simply because it wasn't strong enough? Or did the rim see impact from a rock or whatever because the tire was either at too low a pressure or too small in volume to protect it?

Chandne

When it comes to ZIPP, they do not believe that 1.1 is a good standard so thy test their hookless wheels/rims to 1.5 of max pressure for that wheel. I am not sure about ENVE or any of the others but 1.1 does seem like a low standard. I use ZIPP 303 FCs with 30/32.

PeteHski

While I’m not a big fan of hookless road bike rims, Hambini is a click-bait merchant who has a tendency to exaggerate and sensationalise pretty much everything he talks about.

Dave Mayer

Right, but he has a solid engineering background in bicycles and components and you don't. He has his own business in engineering and testing bottom brackets and you don't. He has thousands of followers who trust his opinions in bike-related issues and you don't.

He doesn't get his opinions from the latest bike manufacturer propaganda and simply parrot them on this forum. Latest is best!

And his style is not substance: he has a deep understanding of everything he posts about, unlike the engineering-poor little bike industry whose decisions are dominated by marketing.

PeteHski

I have a very solid professional engineering background which allows me to filter reality from bs and hyperbole. I don’t follow Hambini, but I have seen a few of his childish video rants. Not very professional IMO. I don’t have any BB issues that require his niche products either.

Mojo31

Comedy genius in this post!

Dave Mayer

If you are an engineer, then you know that disparaging the advice or analysis produced by a fellow professional engineer as "childish" or "unprofessional" and "sensational" is itself deeply unprofessional and in most engineering regulatory bodies would initiate a practice review and possible disciplinary action. Where exactly are you registered?

The way you challenge the work of an engineer is to test and analyze the problem and produce a study. As opposed to dash off few snippets of inconsequential froth, which seems to be your total contribution to this thread and pretty much everywhere else in this forum.

tomato coupe

Pointing out that someone else is unprofessional is not unprofessional.

Dave Mayer

Thanks for that contribution to the subject of hookless and the progress in human knowledge. Among engineers it is the role of professional licensing and regulatory bodies to determine if someone has acted unprofessionally. Using a few profanities in your videos but being technically correct is not unprofessional behavior. But here is a real engineers opinion on the subject of hookless. Skip to 32:00.

If hookless tires were made with steel wire beads, radial plies, and are mounted with high-strength jacks during tire installation and removal, then they would be safe on bicycles. But then who wants to ride on 700gram tires?


Had enough... off to the shop to do some real bicycle work.

elcruxio

There is that. Also car tires are radial whereas bicycle tires are cross ply. Car tires have quite high stiffness compared to their typical pressure. Car tires also have massive steel beads and radial steel belts. Car tire tolerances are also much tighter than what the bicycle industry is able to achieve.

But there are some interesting differences in rims as well.
Firstly car rims are asymmetric in such a way that the bead well is unable to accommodate two beads at the same time. They won't fit and the other side won't be able to stretch that far.

ETRTO flange height for car rims is 17,5mm whereas bicycle rim flange height is 6,3mm. Flange / diameter ratio for car rims is 0,04 whereas for hookless bicycle tires it's 0,01. So quarter of the stretch and slip allowance with higher pressures, floppy cross ply hand mountable tire, sloppier tolerances in both tires and wheels etc.

Compared to car tires and rims, hookless rims that are based on the ETRTO hooked (crotchet) rim standard isn't exactly confidence inspiring.

It would likely be possible to make hookless totally safe, but that would probably require a new standard for rims with some modifications to the tires as well. Whether or not those tires would be compatible with crotchet rims? Unlikely. The safe hookless tire and rim combo would also probably be quite a chore to mount. Potentially something you wouldn't be able to do roadside.
[/QUOTE]

Mojo31

This is not true

tomato coupe

Ummmmmm ........... I responded to your statement. If you don't want others to make comments off the main topic, don't go there first.

Mojo31

Would be interesting to know Hambibi’s actual credentials. Seems that is a bit obscure.

https://hambini.cc/#

phrantic09

Wow. If even some of this is true, he’s more of a French shower than I thought.

PeteHski

He churns out sweary, ranting YouTube vids and acts like an idiot in most of them. It totally undermines any professional credibility he may actually have, so I just don’t take him seriously. I’m sure his BB kits are fine if you need them. I’m not even challenging his work and the idea that I would face disciplinary action from any engineering body for dissing his YouTube rants is hilarious. A bit like your comedy posts.

PeteHski

None of this is surprising to me. I always thought it was highly unlikely that he would have access to commercial wind tunnel time.

Mojo31

What makes me laugh is DM’s suggestion that Trek, Specialized, Giant, Cervelo and other major brands do not hire appropriate engineers for frame design, and that the likes of Zipp do not retain engineers to design their products. Not doing so opens the door to huge liabilities if someone is injured using the product. So, suggesting that they don’t just shows that the person doesn’t know much about the business world turns.

elcruxio

That tracks. In my line of work (dispute resolution lawyer in a technical field) I get access to very high level professionals and I also see a lot of hacks. The pro's tend to be subdued, calm and almost unsure to a point whereas the hacks are often quite brash and exceedingly confident.

I've only ever watched a few minutes of a Hambini video but that was enough to tell me he wasn't A) worth my time and B) an actual professional on the field he's ranting about.

DaveSSS 

Watch the comments in the video about installing car tires compared to bike tires and the reasoning that explains why car tires are perfectly safe, but hookless bike tires aren't.

Then watch this.

Mojo31

My experience is the same. In addition to working with technical experts, I also represent engineering firms.