The tubeless transition: One giant leap for tires?

If you’ve followed bicycle industry news for the past five years, you are most likely aware of tubeless tire technology. It’s especially established in the mountain bike world, where ditching your inner tubes brings a lot of benefits with very few downsides.

But what about for bikes with those funny curly handlebars, you ask? Where is tubeless tech in that realm? You may be surprised that it’s been around for longer than you think.

TECHNOLOGY PRIMER: TUBULARS VS CLINCHERS VS TUBELESS

Photo credit: The Pros’ Closet.

Most of us are familiar with the traditional inner tube, which is a ring- or donut-shaped balloon that gives the classic clincher or tubular bicycle tire its air pressure. In those, the tire carcass exists partly to contain the inner tube’s air pressure and keep it from bursting.

With a tubular tire, the inner tube is completely sewn up inside the tire carcass, which is then glued onto a wheel rim – which is a meticulous process that only race mechanics have the patience for, and done multiple days before a race. This setup is impractical for most folks except for weight weenies and professional road racing cyclists, as repairing a punctured tubular tire basically requires replacing the entire thing, glue and all…or replacing the whole wheel, like what most pro cyclists have their mechanics do.

Most non-competitive cyclists use clincher tires instead, which is really a system comprised of the tire and the rim. You still have the inner tube, and the clincher tire’s carcass is still containing its air pressure. Here though, the side edges of a clincher tire, called beads, are designed to fit into the inner walls of the wheel rim mechanically.

In the event of a puncture, a clincher tire allows access to the inner tube by removing one of the two tire beads. It then is just a matter of either replacing the tube with a new one, or patching it and reinstalling. While still inconvenient, it can be done on the roadside, and is less egregious than having to deal with a punctured tubular. There is always the risk of pinching the inner tube between wheel rim and tire bead, though. This happens either via installing a tube incorrectly, or running too little air pressure – in which case you get a pinch flat or a “snake bite” puncture, with the “fangs” being the two walls of the rim.

As the name suggests, a tubeless tire is one that does away with the traditional inner tube. In basic concept, it’s an evolved clincher: a tubeless tire still has beads that mechanically interlock with the rim. However, removing the inner tube means there is no more risk of a pinch flat, and thus allows tires to ride with lower air pressure. This also now requires the tire itself to be airtight, which was previously the job of the inner tube. The additional, arguably more attractive benefit of going tubeless is that a latex-based fluid sealant can be added inside the tire, so that it can proactively plug up small punctures without having to stop on the roadside or even lose significant air pressure.

Some digging or expert Google-Fu yields that tubeless tire technology has been around for drop-bar bikes since 2006, which Shimano teaming up with French tire maker Hutchinson on one of the very first so-called “road tubeless” systems. Another French tire maker, Mavic, also tried their hand at making a road bike version of their UST, or “Universal System for Tubeless,” in 2017. Unfortunately, neither gained much traction at the time.

TAMING THE TUBELESS BEAST

Removing the inner tube from the clincher system, and expecting it to function as a usable wheel and tire combination, introduces quite a few challenges in the context of road bikes.

After much hesitation, Continental finally committed to road tubeless with their GP5000TL tire in 2019. Photo credit: BikeRadar.com

A major hurdle involves the tolerances influencing the successful fitment of tubeless tire to tubeless-compatible wheel rim. Prior to 2019, it was (and still is) much less of a factor with mountain bikes, but the compatibility situation on road bikes was arguably the Wild West. While many had jumped onto the tubeless bandwagon, German tire giant Continental was a notable holdout, citing the higher air pressures on road bikes, and the lousy, non-standard rim-to-tire compatibility situation. Fortunately the industry players came together and worked out an ISO/ETRTO-approved standard for road tubeless, which emboldened Continental to introduce its own stab at the technology with the GP5000 TL tire in mid-2019.

Photo credit: NoTubes.com

While on the topic of wheels, these too have to be made airtight. Early players in tubeless, most notably Stan’s, introduced their own rim tapes to convert a wheel rim to a tubeless-compatible form, covering the spoke holes peppering the rim bed and making it airtight that way – still a viable solution at present. Later, some wheels themselves started to drop spoke holes entirely, making the rim bed a solid surface of aluminum or carbon fiber and guaranteeing an airtight seal. Those still have spoke nipples, though, so these are dropped into the valve hole and guided into their final locations via magnets.

Finally, the most recent development is the dropping of rim hooks on tubeless wheels made out of carbon fiber. The theory goes that making these rim hooks is supposedly unnecessary for tubeless, and that dropping them should improve the compaction of the carbon fiber and resin, resulting in a stronger, better quality product, while at the same time simplifying the manufacturing process and yielding cost savings. As you can expect, it’s yet another complication thrown in the mix, and the new ISO/ETRTO tubeless tire and rim standard supposedly already addresses this, along with a 73 psi tire pressure cap for such “tubeless straight side” wheel rims.

As with many standards in the bicycle industry, however, it’s all in the implementation…and I plan to put this all to the test in the next installment.

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