Trakhak

He means tubulars/sprints/sewups/glued-on tires.

mstateglfr 

There are a lot, they just dont say ZIPP or ENVE on the rim.

Sy Reene

However, it is interesting to note, that even selecting a tubed setup on Zipps pressure calculator, it suggest only about 85psi for a 25mm tire. They realize anyway that they need to try and make a case that tubeless low pressures are viable.

79pmooney

Probably not. Kevlar could be added to the flange and hook to help keep it together after impact but with both cost and weight added, not likely to happen (unless the CPA went on steroids and insisted without budging that tires stay on.)

Yan 

It's just one anecdote, but I hit a hole on a gravel descent 15 years ago, instantly flatted and crashed a few seconds later because the flat front tire could no longer grip the gravel surface. Later when I went to fix the flat, I realized the rim was split and the tire was ripped. The tire was still on the wheel. I was not happy about having to buy a whole new wheel and tire as both were relatively new.

In this case I still crashed, but I think I would have remained upright if I had been on asphalt. Of course that's with an aluminum rim.

Yan 

That makes it even worse.

So hookless rims are not just limited in maximum safe pressure, they're also worthless with 25mm tires. One fault has become two faults.

25 is only 10% narrower than the currently fashionable 28.

As a wheel owner I want myself to be the decision maker in what tires I run.

79pmooney

Still, I bet your crash was a friendlier one than Gendt's over the bars. (Your front wheel "washed out", no? More skin, less faceplant?)

Yan 

Washed out and I flopped over on my side, yes. Definitely better than flipping head over heels on my face.

79pmooney

Exactly the kind of stuff CPA should be advocating for its riders. Wheel systems that minimize career or photo-op ending crashes. UCI should have little difficulty with that concept also except they are comfortably in bed with the manufacturers.

Yan 

Not all manufactures thankfully. DT Swiss says it doesn't make hookless for road, due to safety concerns.

wayold

Well I guess I'm in the hookless camp. In my case the gravel wheels I wanted were only available with hookless rims, which did give me some pause. But the tires I'm running are hookless compatible and just about exactly in the middle of the recommended range of diameters for the rim (43mm tires on 22mm IW rims). Finally I'm running these at 30-35 PSI - well below the pressure maximum. So I've convinced myself I have little to worry about, Guess I'll find out.

PeteHski

Well it also depends on rider weight, rim width etc. If you go to 23c on 15mm wide rums Zipp’s calculator advises close to 100 psi for an 80kg rider. Tubeless only reduces pressure by 2psi. Also note that rolling resistance increases much more above the optimum point than it reduces below it. So it makes sense to advise slightly lower pressures.

For reference, Pro riders using 28mm tyres on modern aero rims are racing at around 65 psi. Even lower for races like Paris Roubaix, where they are mostly now using 30 or 32mm tyres.

PeteHski

Most hookless rims are too wide for 25mm tyres. They are only 10% narrower than 28mm, but on wider rims (say 23mm internal vs 15mm) optimum pressure drops from around 90 psi (25c tyres on 15c rims) to 65 psi (28c tyres on 23c rims).

Sy Reene

Well, yes, but I entered in the test parameters that the aforementioned Silca4b article mentioned. 25mm Conti tires (WAM mentioned of 25.8) and system weight of 190lbs. No 23mm tires. With Zipp's calculator though, you do have to guess what inner width of the rim to use that it thinks would yield a 26mm inflated width. Anyway, results in the calculator are a decent-sized departure from the 110psi shown in the graphs. Even if you can finagle the calculator to give you a 90psi result, 20psi lower isn't "slightly lower" IMO. FWIW, Silca's own calculator really isn't too much higher.

PeteHski

If you put in 25 mm tyre width on a 15 mm rim and choose the thin casing option, then you get exactly 100 psi for a hooked tubeless rear at 190 lb total weight. Silca recommends 95 psi for a 26 mm measured tyre width for racing.

Sy Reene

That gets closer, but were Zipp 404 Firecrests only 15mm inside width back then (which was 2014)?

PeteHski

It looks like they were 16mm internal width, which for tubed tyres gives 100psi and 98psi for tubeless.

So it looks like they advise to run a little lower than the break point on the Silca graph. This makes sense given that you gain a lot more resistance by going too high vs too low. If you look at the table in the Silca blog, it shows the power loss for +/- 10 psi from the minimum. You lose only 1W from being 10 psi too low, but lose up to 9W from being 10 psi too high.

So given that road surfaces are pretty variable it is advisable to set pressures on the low side of the nominal optimum. It also provides a slightly better ride and lower resistance on rougher than average roads.

Much wider modern rims (current Zipp 404 is 23mm internal) combined with 28-32 mm tyres greatly reduce the optimum pressure and that has allowed hookless to become viable for most riders.

Personally, I still prefer the safety margin of hooked rims because I’m an 80 kg rider and not bothered about saving every last gram of rim weight. I currently run 30mm tyres on hooked 22mm rims at around 65psi.

Dave Mayer

We more experienced cyclists have had multiple blowouts on both clincher (hookless or otherwise) and tubulars. The difference is binary: on the clinchers the result is a desperate struggle to stay upright, even at a jogging pace. There is always a big risk of the tire coming loose and jamming up in something.

In contrast, a tubular blowout, even at high speed is far less dramatic, with a much higher chance of riding it out. The tires stays glued tight on the rim, and you actually have some cornering ability and traction.

Again, I think for high-performance riding, with tubeless and hookless, the industry is turning itself inside out with increasingly weird and elaborate solutions for a problem that tubulars never presented. Inserting slime and a pool noodle inside a tire that cannot be inflated to racing pressures is simply an indication of that desperation.

Yeah I know, yada yada yada, you're scared of getting a little glue on your hands, and you only ride your bike to the coffee shop, so you don't need lightweight wheels, you've never ridden (ever) on tubulars. I just hope that the industry and the pro teams allow their contenders to ride on the wheels that they want to ride on for performance and safety reasons, as opposed to a weird suboptimal wheel/tire combo (hookless/tubeless) that the manufacturers want to sell to weekend warriors.

spdntrxi

^ racing pressures ? what the hell is that. 120psi like the old days.

79pmooney

What does the pressure matter? Any blowout at any pressure at 45 mph on a sewup is much less stressful than any blowout or deflation for any other reason with clinchers or tubeless at that same speed. Ask anybody who has done both. Or go try them yourself. Or ask de Gendt.

elcruxio

This thread got me thinking about the early days of road tubeless when tires were coming easier to obtain but tubeless rims were still expensive and scarce.

I did what many other people did and just taped up non tubeless rims so that they'd hold air. When you got the tires seated the system worked great. I recall that the biggest hurdle was always getting the tire to seat (not really an issue with modern tubeless rims). The seal was sometimes somewhat sketchy so you'd need a bit more sealant than you do these days, but the air loss eventually stopped. In one case it took a bit longer to make the tire hold air but it eventually did. Of course if you lost pressure the tire instantly fell off the bead shelf and burps were an issue with lower pressures (mainly mountain biking)

There were blowouts, BUT they were always happening to people who, against sharply given advice, decided to try tubeless with non tubeless rated tires, such as the GP4000 standard version or a tire with a steel bead. When actual tubeless tires were used, there didn't seem to be many issues.

One of the articles posted here previously claimed that when the tire is working properly the hook isn't doing anything. I'm beginning to wonder whether that claim is entirely true.
A hooked tubeless rim has three contact surfaces for the tire. The bead shelf, the sidewall and the hook. A hookless rim has two contact surfaces, because the hook is missing. But a non tubeless rim also only has two contact surfaces as the rim shelf is usually pretty diagonal. Or perhaps it's 2,5, since there's maybe some contact with the bead shelf.

Anyways there were no pressure limits with non tubeless rims, nor were there really any tire size limits.* You could pump the tires to as high pressures as you'd pump them with tubes. I used both 25mm and 40mm tires tubeless on my 14mm ID rims. Since I'm somewhat large, I need to use pretty high pressures. When i was using 25mm I'd pump them to 7-8 bar or 100-115 psi.

I never had a blowout or any other issue after I'd gotten the tires mounted and to hold air. It was only when I got my first set of actual tubeless rims I realized how janky non tubeless rims were in tubeless use.

Considering how narrow the suitable tire width range is for a given rim width and how low the hookless max pressures are, I just start to wonder whether the hook is somewhat essential.

*When I say there were no limits, I mean people were experimenting with that stuff with their own risk.

PeteHski

I just think "weekend warrior" should be on the Dave Mayer bingo card

phrantic09

You left out platinum card.

Could you be any more of an elitist French shower?

PeteHski

IME, deflations on lower pressure tubeless tyres with sealant are slow and benign. Also very rare. I’ve had 1 in the last 4 years, from a large cut that was too big to self-seal. What happened to TdeG was due to the tyre suddenly coming off the rim, which fortunately I have never experienced on any tyre. I’ve run tubs, clinchers and tubeless setups over the years and tubeless have been the most reliable ie virtually no flats and the easiest by far to repair roadside with a plug kit. I haven’t used “pool noodles” and I don’t think many riders on tubeless use them either. Also never used hookless rims.

PeteHski

It’s his usual MO and whenever he gets called out his “supporters” accuse people of being unfair or ganging up on him. His posts are always a trollish mix of complete bs, cynicism, Big Bike conspiracy theories and patronising superiority.