Valves exposed: the whole squalid truth! Well, kind of...

We’re tackling valves – everything you need to know about them, including the options open to you and whether or not you should use the dust cap.

We’ve always liked to bring you hard-hitting journalism here on road.cc. Historically, who can forget Eurobike 2011: The rise and rise of the chain catcher, for example? Cutting-edge stuff, I think you’ll agree. We don’t shy away from the big issues.

Before we get stuck into valves, let’s make sure that everyone is up to speed on the basics. This is a Presta valve (above).

And this is a Schrader valve (below), which you'll also see used for car tyres and various other applications...

Presta is skinnier, and rather than being hidden away inside, the valve core is partially exposed. You might find Schrader valves on lower-end mountain bikes, hybrids, folders, and kids' bikes, but Presta rules the cycling world. There were more Schrader-equipped mountain bikes in the past, but tubeless has been the norm in off-road riding for a long time, and tubeless valves are Presta (or close cousins). 

> Should you get tubeless tyres? Are they your best option? 

Although some smart heads fit both Presta and Schrader, as a rule, you'll need a pump attachment that's specific to the type of valve you have on your bike. 

Right, let’s get cracking…

We mostly use Presta valves, but would Schrader make more sense?

US company Jones Bikes switched from using Presta to Schrader valves on its bikes last year. That’s not exactly front-page news for us over here in the UK, but it brought up an interesting point.

Jeff Jones said, “After comparing and testing Presta and Schrader valve stems, it makes sense to change from Presta to Schrader.

“We flow-tested 10 tubeless valve stems, including Presta, Schrader, and a Fillmore high-flow stem, to see the differences and to find the stem with the most flow because tubeless valve stems with a higher flow rate make mounting tubeless tyres easier.”

Jones Bikes devised an experiment using water to find out which valves offered the highest flow. It tested valves with the core in place, and valves with the core removed. You can check out this video to find out exactly what happened…

Watched it? If not, spoiler alert! According to this test, the Jones Spec Schrader valve stem – with the core removed – offered the highest level of flow, which isn’t surprising. Jones Bikes probably wouldn’t have bothered making a video if its product didn’t do well. Other Schrader valves with the core removed performed strongly too.

Prestas with the valve core in place were down at the bottom, while Prestas with the valve core removed offered various flow levels. According to Jones Bikes, though, if you’re inflating a tyre set up tubeless – which requires a certain punch to make it seat – Schrader makes more sense.

Why do we mostly use Presta in cycling?

“In the 1890s the Presta valve stem was designed with a smaller diameter,” says Jeff Jones. “This allowed for the drilling of smaller holes in the narrow wooden rims of the time, leaving more wood behind to reduce the risk of cracking.

“Now, with wider aluminium and carbon fibre rims, the small Presta size is not needed. Schrader is wider, sturdier, and has a removable valve core that doesn't clog.”

Of course, Jones Bikes wants to beat the drum for its own valves (above).

“Jones Schrader valve stems have a larger inside diameter which gives them more flow than high-flow Presta valve stems and other Schrader stems,” says Jeff Jones. “It’s also lighter than many Presta valve stems.”

The bike industry should switch to Schrader, then? Case closed? It’s not as simple as that. For a start, Jones Bikes uses big ol’ wheels and tyres, but there’s a whole other side to cycling.

Zipp’s product manager Nathan Schickel says, “When putting holes in a carbon rim, it is always better to move toward the smallest hole possible. Creating a bigger hole means more reinforcement around that hole, which means higher weight. Because of this, we stay with Presta.”

Rims come in different widths, with road models tending to be narrower than mountain bike options. This affects the amount of space available for the valve. 

Hunt Bike Wheels founder Tom Marchment says, “If you did try to use Schrader with a road-width tubeless rim, you would be making quite a large hole in the small area where you’re trying to create a seal and fit a tyre bead inside the rim sidewall. 

“From a tubeless point of view, the hole in your rim needs to be big enough that when you put your valve in with a rubber bung, it meets in a way that the rubber seals really well. With a Presta valve, you don’t need as large a rubber bung because your valve stem is smaller. 

“When you’re talking about a road rim with a 21mm internal width and you need shoulders [in the tyre bed] for tubeless tyres [to help the bead seat], it starts getting a bit tight if you have to make the hole 9-10mm wide [for Schrader] in the rim bed instead of being 7-8mm wide [for Presta].”

“The external diameter of the aluminium at the bottom of a Presta valve is 6.7mm, and it’s 8mm on Schrader, but the bung is wider than that. The hole on the inner side of the rim needs to be considerably larger because the rubber part extends out.”

Zipp’s Nathan Schickel says. “We’re still choosing Presta primarily for weight and also because we haven’t yet found a better solution that meets the needs of our customers: to fit in a small hole in the rim; allow for a high flow of air into the wheel for tyre seating; does not clog, but allows for sealant to pass through easily; fits standard pumps and CO₂ inflators without adaptors.”

In other words, don’t expect a mass change from Presta to Schrader anytime soon.

How to get more air through a Presta valve

What about getting more air through Presta valves to help seat a tubeless tyre? You can use a CO₂ pump (some brands say that CO₂ exposure can cause their sealants to separate, others say it's fine with their products) or a floor pump.
 
A two-stage floor pump can be useful. Initially, you want a high-volume pump that seats the tyre and pushes a large amount of air inside. Beyond about 30psi, it’s useful to have a high-pressure pump that allows you to get more air inside without the handle being too hard to press. 

Something like the Topeak JoeBlow Tubi 2Stage floor pump that we reviewed allows you to switch between the two modes, and it does an excellent job. 

> Review: Topeak JoeBlow Tubi 2Stage floor pump

A floor pump with a pressurised chamber gives you a bit of extra oomph – something like the Bontrager TLR Flash Charger floor pump that we reviewed a few years ago. Essentially, you pump loads of air into a chamber and then let it into your tyre in one go. 

> Check out our review of the Bontrager TLR Flash Charger floor pump

Plenty of other brands offer something similar. The JoeBlow Booster is very good, for example. Again, you charge the in-built chamber and blast the air into the tyre in one go.

> Review: Topeak JoeBlow Booster track pump and tubeless inflator

It’s common to remove a Presta valve core to inflate a tubeless tyre the first time. Once seated, you can disconnect the pump head, attempt to replace the core as quickly as possible before all the air comes out again, and re-inflate.

There's a bit of an art to getting the core in before all the air has escaped (the hammer in the vid is just for illustration purposes; there's no need to start whacking your tyres).

Failing that, you can just let the air out and hope the tyre has stayed seated, or at least partially seated, so it's now easier to inflate.

Some brands have introduced their own tubeless valves that are designed to make things simpler without the need for a larger hole in the rim. Reserve says that its Fillmore Valves, for example, offer three times the airflow of standard Presta valves “to make seating tubeless tyres a snap”. 

“The patented Fillmore valve represents a game-changing leap forward in technology, with a high-flow design that eases tubeless setup and eliminates the traditional, delicate, clog-inciting valve core of yesteryear,” says Reserve.

When Tom Weijand reviewed them for road.cc, he said, “The Reserves are not strictly Prestas, they're a Presta-compatible reimagining of a bike valve that prioritises high flow rate and prevents clogs. And they succeed. Wildly.”

> Read our review of Reserve Fillmore Valves 

We gave the Reserve Fillmore valves our Editor's Choice award in the road.cc Recommends Components of the Year 2023/24. They are priced individually at £34.99 (for the 50mm version).

Topeak has a very different solution.

“In most cases, inflating a tyre without a compressor means removing the valve core to allow a higher flow of air to enter the tyre and seat the tyre bead, but refitting the valve core without the tyre becoming completely deflated and the bead coming away from the rim bead is a real challenge,” says Richard Jones of Topeak’s UK distributor Extra. 

“The Topeak TubiHead is a valve head that attaches to Presta valves. You can then unscrew the valve core and remove it from the valve and inflate the tyre, all without the need for removing the pump head from the valve. Then, whilst holding the pressure within the tyre and TubiHead, you can refit the valve core in one seamless action without air loss or messy sealant leaks.”

Getting that? You’d prefer a video, right?

It’s a clever idea. Does it work? Absolutely. We had our man Mike Stead on the case a couple of years ago, and he rated the design highly. A Topeak TubiHead Upgrade Kit is £29.99.

Integrated versus removable valve cores: who wins?

Some Presta valve cores are integrated (below)...

...while others can be taken out and replaced via a tiny valve core removal tool (below). There are advantages to each. 

If you use a tubeless valve with a removable core, you can take it out and top up the sealant through the hole without needing to take the tyre bead off the rim. You can also replace the core with a valve extender that has a core at the top (below, red), for use with deep-section wheels.

If you have a new inner tube with a removable core, make sure it's screwed tightly into the body of the valve so that it doesn't accidentally come out the first time you want to top up with air.

With an integrated core, there’s no chance of accidental removal when you inflate your tyres.

You can use valve extenders with integrated core valves – but only the type that fits over the top of the existing valve core (above, brass) rather than replacing it. 

How can you combat clogging?

Clogging can be an issue with tubeless valves. The clearances in a Presta valve are smaller than some holes in your tyre that the sealant is designed to plug, so it’s not surprising that they can get bunged up.

What can you do about it? You can remove the valve core and clean out hardened sealant in the valve stem with something like an old spoke. Topeak has a Tube Valve Cleaner especially for the job (£12.99). It allows you to remove the core and then clear any clogging.

If there’s sealant clogging the valve core, you can carefully try to get it out with a pin or, worst-case scenario, replace it.

Like the Fillmore Valves mentioned above, the 76 Projects Hi Flow No Clog Tubeless Valves that we reviewed last year are designed to avoid the problem in the first place. Chad Scallan described them as an “innovative and effective way to combat clogged valves” and “a gamechanger” in this respect. The internal clearances are much greater than on a Presta valve to avoid the build-up of sealant.

> Review: 76 Projects Hi Flow No Clog Tubeless Valves

“If you're forever finding yourself stuck with clogged-up tubeless valves, or you’re just looking into setting up your bike with tubeless tyres, these valves are ideal,” Chad said. “They improve pumping efficiency and they don't clog up – exactly what’s needed in a pair of tubeless valves.”

Should you use the knurled valve lock nut?

If you have your tyres set up tubeless, you have to use a tubeless valve, of course, with a lock nut that's an integral part of the system, holding the bottom of the stem tightly on the rim. If you’re running inner tubes, you’ll usually get a valve lock nut – a knurled collar that's sometimes called a rim nut – threaded to the stem (not always; some valve stems aren’t externally threaded). Should you use it?

Some valve lock nuts have a shoulder for centring a Presta valve stem in a Schrader-sized hole. Others have a uniform thickness. What if you’re using a Presta valve in a rim that’s made for Presta?

“The nut serves a few purposes,” says Schwalbe's Tim Ward. “It holds the valve in place so that when inflating from flat, you can push the pump head onto the valve without the valve disappearing into the tyre.

“It can stop the valve rattling in the rim, and to some extent, it can help to prevent valve tear-off caused by the tyre slipping around the rim slightly under heavy braking forces.

“All Schwalbe butyl tubes with either a Presta or Schrader valve have a threaded valve stem and rim nut. However, our Aerothan TPU [thermoplastic polyurethane] tube has a valve stem made from lightweight plastic (and is therefore less likely to have any rattling issues) that's not threaded and has no rim nut. Various other tube brands on the market don’t have threaded valve stems on some of their tubes.

“Is a rim nut essential? Probably not, and it's largely down to personal choice. I always fit one, more out of habit than anything, and a valve dust cap as well (see below), as keeping water, muck, and road salt out of the valve just seems like a good idea to me.”

Some people swear by the lock nut to hold the valve in place when using a pump. However, Vittoria suggests only tightening it in place after you've pumped up the tube. 

“Valve tear-off can be caused by the valve lock nut being threaded onto the valve too tightly before the tube is inflated – the valve can then tear away from the inner tube when the tube is inflated,” says Vittoria. “For this reason, we recommend only threading the lock nut onto the valve once the tube has been inflated.”

We did a quick survey here at road.cc and off.road.cc and found that most of us do use the lock nut when riding with inner tubes.

“I fit it, otherwise, the rattling of the valve in the rim drives me insane,” said our man George Hill.

Stu Kerton, Suvi Loponen, Matthew Page, Simon Withers, Steve Williams – in fact, everyone else on the team whom I hassled for an answer – said they use the lock nut too. 

Me? Those collars go straight into the ‘just in case’ section of the toolbox and never re-emerge – but it looks like I’m very much in the minority here. Rattling? The voices inside my head must drown it out.

What about the dust cap?

In terms of function, what does the cap on a Presta valve do? It might stop the top of the valve from damaging the inner tube when it’s in the packet, your saddle pack, or a rear pocket, but what about when you're riding? 

“We recommend that you use the caps as they prevent dirt from coming into the inner tube or tubeless system,” says Alexander Hänke, who works in product management in Continental’s bicycle tyre division. 

“The cap prevents the valve top from corroding. If consumers bin them, it is not satisfying, but there is no legal requirement to use them.”

That’s the official line. Some people think they’re the finishing touch too.

“When it comes to dust caps, I guess some people like how they look,” says Zipp’s product manager Nathan Schickel.

Again, we had a discussion among the road.cc and off.road.cc teams to get a snapshot of opinions.

“I never use them,” says Steve Williams. “The dust cap serves no purpose on a Presta valve.”

There are plenty of fans, though.

Aaron Borrill, editor of off.road.cc, says he uses the dust cap for mountain biking because it offers a tiny bit of protection against stones, rocks, and anything else that’s flying about.

Director of content Tony Farrelly says, “When I ran tubes, I used valve caps until I lost them, but after a few months of winter riding, I had the core snap off on more than one occasion, once in the pump, which was a mighty pain.

“If you're running tubeless, that core is even more important, so it's even more crucial to protect it if you ride in all weathers.”

It’s worth pointing out that some valve caps have a side hustle, too.

“We've designed a valve cap with a little core remover on the end,” says Hunt’s Tom Marchment. “It allows you to take the valve core on and off more easily. We've already implemented that on mountain bike wheels, we're about to add them to gravel wheels, and might well add them to road wheels soon.

“It means that if you need to re-inflate after putting tyre bungs/anchovies in a puncture, you can take the valve core out for higher airflow.”Plenty of other brands, like Peaty’s and Muc-Off, have valve caps that do a similar job – Peaty's also has a spoke key – so you might want to check before you bin ’em in future. 

Let us know where you stand on these big issues in the comments below.