friends riding mountain bikes down trail
A new valve design from Reserve, the wheels division of Santa Cruz Bicycles, promises a better, more user-friendly experience that’s ideal for modern bikes that run on tubeless. (Photo: Thomas Barwick/Getty)

This New Valve Could Make Tubeless Tires Not Suck

Reserve’s Fillmore is a modest innovation with big potential to make life easier for cyclists

friends riding mountain bikes down trail

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There aren’t many technologies as ubiquitous in cycling as the Presta air valve. So it’s surprising that, in the roughly 100 years since its invention, it’s basically never changed. Until now. A new valve design from Reserve, the wheels division of Santa Cruz Bicycles, promises a better, more user-friendly experience that’s ideal for modern bikes that run on tubeless.

First, some brief valve history (nerdery) is in order. In 1887, John Boyd Dunlop created the first commercially successful pneumatic tire. A few years later, August Schrader invented the spring-loaded air valve that bears his name and is found today on everything from car tires to suspension forks to department-store bikes. Presta valves appeared sometime between the late 1800s and the early 1920s (patent databases don’t have a firm record of its invention) and is now found almost exclusively on high-end bicycles.

In that application, the Presta valve offers two relevant advantages. First, because of its smaller air volume, a Presta valve makes it easier to inflate narrow, high-pressure road tires with less force. Second, the valve itself is about half the diameter of a Schrader valve, and a smaller valve hole means a stronger rim. Both helped Presta catch on as a preferred valve technology for bikes, and for decades nothing changed, because it didn’t have to.

Then, in 1999, a trio of French wheel and tire brands—Hutchinson, Mavic, and Michelin—launched the Universal System Tubeless. And ever since, riders have been trying and struggling to install tubeless tires with Presta valve technology. Presta valves, which work fine when part of an inner tube, simply aren’t great for tubeless systems. The limited airflow makes it tough to inflate and seat a tubeless tire bead initially. They’re also prone to clogging with congealed sealant, which then limits airflow even further, and eventually the valve core gets so gummed up that you have to replace the whole thing.

I have personally used the following approaches to try and install tubeless tires: air compressor, gas-station inflator (with valve adaptor), CO2 cartridge, tubeless charging chamber, tubeless charging pump, or exhorting any number of gods. But those methods are either relatively expensive and require specialized tools, or they’re unreliable, dangerous, or all of the above. What almost never works is a standard floor pump, so I employ this trick: I use a tube to seat half of the tire bead, and then I remove the tube and seat the other side with a pump, or a charging chamber followed by a pump and a prayer.

So I was intrigued by Reserve’s new Fillmore valve ($50 per pair), because it promises easy installation with nothing more than that simple shop tool. Public reception indicates that mountain bikers are also intrigued, although there’s some grumbling about the price (more on that in a minute).

The big difference is that Reserve says the Fillmore has three times the airflow volume of a Presta valve. The reason airflow volume is so important for a tubeless install is that you need a lot of air going into the tire—really fast—to push the tire bead from the rim bed’s center channel out to the sidewall, where it locks to form an airtight seal. Presta valves just aren’t made to allow that.

All valves have a rubber seal of some kind to stop air from escaping. In the case of Schrader and Presta, that’s a cylindrical gasket inside the valve core; Schrader valves also feature a spring to keep it shut, while the Presta gasket is held in place by air pressure alone. In both cases, because the gasket is inside the valve core, it takes up valuable space.

The Fillmore addresses that with a high-flow design that basically opens up the real estate inside the valve. Like Presta and Schrader, it’s a poppet valve. But the gasket lives at the base of the valve, instead of inside the valve core. With less stuff inside the core, the Fillmore allows higher airflow while maintaining the same diameter as Presta valves. This means the Fillmore fits all existing rims, so there’s no need for new industry standards or for riders to buy new wheels. (It also works with pretty much any floor or mini pump.) A secondary benefit of putting the O-ring at the valve base is to stop sealant from entering the core, where it can congeal.

The Test

About two months ago, I got a set of Fillmores, just in time to replace the worn tires on my singlespeed, which I’d been putting off. The singlespeed is mostly a winter trail bike, a kind of riding that works best on a tubeless setup, to allow the low pressure that produces a larger contact patch for better traction and flotation. I unfolded a pair of Specialized Butcher Grid tires, stripped the old tires off, and thoroughly cleaned the rims of dried sealant.

The Fillmore is a universal-style valve, intended to fit almost any rim-bed channel. Although Reserve allows that there may be a few incompatible wheels out there, I had no issues even with a decade-old Mavic wheelset. The Butcher Grids went onto the rims pretty easily, which is sometimes an indication that a tire bead will be especially leaky on installation. So I injected sealant, attached the floor pump’s chuck with a small prayer, and began pumping vigorously.

Typically, what happens in this scenario is I pump until I’m cross-eyed and the tire casing expands and contracts like a bellow as air leaks around the bead. Try as I might, I can almost never force enough air into the tire or do so fast enough to seat it against the rim, so I have to turn to a tubeless charging system. With the Fillmore, the casing inflated and … miraculously held. I pumped faster. The gauge rose to 10 psi, then 20. I kept going past 40 (you should overinflate initially to fully seat the bead, but never past the maximum listed pressure on the tire or rim, whichever is lower). Just above 45 psi, I flipped the pump chuck off and spun the wheel on its axle, bracing for the aerosolized mist of sealant that might come from a gap in the bead seat. Nothing. The installation held—and on the first try. No compressors or chargers. No “One Weird Trick,” like soaping the rim sidewall to get the tire bead to slip more easily into place. No cursing even.

So Reserve seems correct: the Fillmore’s higher airflow makes tubeless installs far easier. Subsequent efforts with Maxxis tires on the more modern carbon wheels of my Ibis met with similar results. Not enough time has passed for me to judge the sealant-clogging claim, but the way the valve is designed, it makes sense it would be less prone to that problem.

The other aspect I can’t evaluate yet is its durability, especially the main O-ring seal. Poppet valves are an old, proven design, so I’m not worried about that. The issue is more about waiting to see if Reserve got the manufacturing right.

Right now the Fillmore is only available in one length, which fits rims with a depth of less than 29 millimeters (i.e., mostly mountain-bike wheels). But Reserve says longer versions, which will fit road and gravel wheelsets with rims up to around 65 millimeters deep, are on the way, hopefully by April (supply chain willing).

The biggest complaint, at least from comments I’ve seen, is its price. The Fillmore is $50 a pair, about $20 to $25 more than most tubeless Presta valve pairs. A 100 percent premium! No wonder people are upset. But that kind of percent-based comparison, which is a great way to assess the relative value of high-price upgrades like wheels, doesn’t work nearly as well for low-cost items. I mean, we’re talking about $25 here. (If you want to be upset about something, be mad at the industry for charging you $25 for replacement valves for two decades before doing anything to address the basic shortcomings of the design.)

I’m not the guy to tell you to spend money on bike stuff for some theoretical gain: it’s dumb to drop $300 on carbon-fiber handlebars, when said bars will improve your ride experience by roughly 0.03 percent over the $100 metal bars they’ve replaced. But when you’re talking about stuff that really impacts your riding or maintenance experience, like tires or handlebar tape or, in this case, valves, I’m all for spending more on quality. With the Fillmore, an extra $25 produces a noticeable benefit: a reliable, low-hassle method to install tubeless tires, which equals more time to ride.

If the Fillmore ends up lacking durability or leaks air or is prone to clogs, I’ll report back and say so. But my initial experience is that it’s exactly what the bike industry needs more of: simple, relatively affordable solutions to persistent problems that riders have been dealing with for too long. Kudos to Reserve for spending its research and development resources not on chasing marginal gains but on something that might actually make life better for lots of riders.

Lead Photo: Thomas Barwick/Getty