What's the Secret Behind No-leakdown Tubeless?

Tubeless is the prototypical example of what is going on in the bike industry today: advanced tech that is great in theory but janky in practice. Tubeless, along with internal hydraulic brake cables and integrated front ends, have conspired to make my cycling life pleasurable/miserable.

My mission over these past 2 or so years has been to try to make all this new and inspiring tech work for me while exhorting and pestering brands to bridge the gap between the on-paper great tech, and the user-friendly great tech. Consider what I’m writing today illustrative (I hope) to readers, as well as a ratcheting up in my pestering if you’re a wheel brand.

I stumbled on a surprising factlet that I promised to pursue. CADEX road tubeless wheels and tires don’t leak down. And I mean, not a pound of pressure, over a week after inflation, and this is before adding sealant. I am not a tubeless expert, but I have not found this ever to be the case in any other tubeless applications, road, gravel or MTB, in my experience. So…

Is it the wheel? Is it the tire? Is it the combo of this particular wheel and tire? This is what I set out to determine, and I’ll just tell you straight out what I found: It’s primarily the wheel. I say this because I mounted other tires on CADEX wheels – and in each case I was careful to use CADEX wheels and tires of various brands that had never been exposed to sealant.

Let’s rewind. A couple of months ago I took possession of CADEX’s new wheels and tires for road. We’re talking primarily about 28mm road tires here, on both road and aero wheels (42mm and 65mm). Yes, the 42mm road wheels are also used for gravel, at least by CADEX pro Josh Berry, and this top gravel racer hasn’t been able to break them yet (I’ve been keeping track).

CADEX is part of the Giant Group of brands. The performance features of this wheel begins to make sense when you consider Giant’s imperatives as a bike brand. If you’re going to do what Giant has done, and ship bikes not tubeless ready, but tubeless, you can’t ship a bike with sealant installed. Your LBS doesn’t know when that bike is going to be sold, and it’s too much of a burden to clean and reinstall sealant every several months in all your Giant bikes. But these tubless wheels can’t leak down, because that same LBS can’t spend an hour every morning inflating tires on the showroom floor. Hence a tire/tube combo that won’t leak down, at all, pre-sealant.

As my main control tire I used Schwalbe Pro Ones, in both 25mm and 28mm, because I have more faith in the fidelity of Schwalbe tubeless than I do in any other tubeless tire brand. What I found is that CADEX wheels with Pro Ones also do not leak down. if you put these Schwalbe tires on CADEX wheels, sealant or no, the tire will stay inflated for a week, losing almost no pressure. I could find almost no difference in the performance of the CADEX or Schwalbe tires on CADEX wheels as regards leakdown.

What is the secret sauce? I don’t know for sure. But if you put these wheels up to, say, a Zipp 303 S, there is a lot in common. Both wheels use hookless beads. If you look at the sidewalls of each rim you can see this. ENVE, HED and others have embraced hookless on most of their new rim designs.

Both the 303 S and the CADEX wheels come with tubeless tape pre-installed. I think this is a biggie. In the case of CADEX, I suspect this brand took a very hard look at the tape it uses. I have not been overly impressed with a lot of the tubeless tape on the market. If I was another wheel brand manager, I would look at the tape CADEX uses.

CADEX wheels also come with valves pre-installed. Other wheel companies don’t. Why? Because other wheel companies don’t assume their wheels are going to be used tubeless. This ambivalence is a mistake in my opinion. Pre-install the valves. Make the customer uninstall the valve if he or she wants to ride with a tube. (It’s not hard to remove a tubeless valve.) By preinstalling the valve, the customer has no choice or question on how or which or whether the brand’s valve will be installed.

The CADEX valve is, on the inside, especially form fitting to the well of the rim (see above). This is a big thing. In my opinion, one of the big reasons CADEX wheels don’t leak is that CADEX spent some real time making sure this critical area is leak-free. Small point maybe, but the CADEX valve has a similar form fit on the outside of the rim (see below). Some tubeless valves offer this; some don’t. If a valve is made this way, you can put pressure on the fixture that mates with the rim without pressuring the rim itself.

All this stuff is pretty easy for wheel makers to do, and it takes the jank out of the tech. And just consider this anecdote as a testament to how screwy this industry is. I’ve got “tubeless ready” gravel tires that have, etched into the sidewall, 80psi max. However, when pressured to 80psi air leaks out the sidewalls of the tires. Why? Because it’s only supposed to be ridden up to 80psi if you have a tube installed. This tire is meant to be ridden at more like 35psi or 40psi if you ride it tubeless. But there’s nothing about this printed on the tire’s sidewall. This well-known tire brand is ambivalent about how its tire should be ridden, so it knowingly prints what amounts to misinformation on its own product.

CADEX has jumped into road tubeless with both feet; it has chosen not to engage in dual-use message mixing; and is therefore at liberty to build, assemble and finish a product for tubeless use.

I’m continuing my experiments with wheels and tires. I have CADEX, Zipp, HED, Reserve, DT Swiss and ENVE wheels around the workshop and I suspect I’ll be getting some more. I’ve got CADEX, Zipp and Schwalbe tires I’m swapping around, and I’m going to try to figure out whether any of these tires do not provide the seal I’m hoping for, and what I can do to make an “ambivalent” wheel a supercharged tubeless-specific wheel that performs like the CADEX wheels with which I’m so impressed.

I’ll report back as I learn more.