This is where foam inserts for tubeless gravel tyres come into play, making them the best upgrade for your gravel bike you didn’t know you needed. The concept originally came from mountain biking downhill but gravel is a better use case.
What’s the point?
If you ride tubeless already, you know the added benefits it provides. Running tyres at lower pressures improves speed, rolling resistance, traction, comfort, and reduces punctures. If you don’t run tubeless yet, chances are high your rim and tyres are already “tubeless ready”, so this addition may just push you to adopt both at once.
Gravel riding involves passages of rock fields, thick exposed tree roots and deep ruts caused by water runoff or the countless passages of other riders taking the same line. Riding at lower pressures means it’s easy to bottom out when you confront these and other obstacles at the wrong angle or accidentally.
What happens when you bottom out? You get a pinch flat which may damage your rim, rip the sidewall of those expensive gravel tyres you just bought or cause you to crash, hard. Foam inserts are here to solve some of these problems and take your tubeless setup, and you’re riding, to the next level.
How do they work?
They aren’t your average pool noodle! Inserts are made of closed-cell foam, which is sturdier and stiffer than its softer, open-cell sibling. When you think of foam, open-cell is probably the one that comes to mind but it’s not the same. The inserts fill in some of the interior volume, providing an added level of support to the tyre, which comes with added benefits you’ll discover shortly.
The inserts are actually foam rings that sit just above the rim’s tyre bed. The tyre fits over it, and the space above and below the insert allows the liquid tyre sealant to flow freely. Inserts come in different widths and require a special valve stem that has the inner air duct parallel to the rim as opposed to perpendicular to it.
Why you need it
Foam inserts keep the tyre from getting crushed flat on impact. This prevents burping that can happen too, which can lead to fluid loss or a flat. The inserts act with the tyre’s supple sidewall casing, adding an extra level of support to prevent tyre and rim damage and reduce the rebound.
They provide added ride security as you’ll never lose or roll the tyre either. The added support means you can flirt with even lower tyre pressures and keep more rubber on the ground. They even add a layer of suspension to your rigid gravel bike, making the ride even smoother and improving speed and traction too.
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Thanks to foam tyre inserts, you can ride a flat home if you have to without damaging the rim or tyre. Proceed with caution at lower speeds but you could do it in a pinch. Some riders don’t even notice they’ve flatted until the end of the ride. Do you need them on every ride? Probably not but they are perfect for the small percentage of super gnarly terrain or singletracks that you come across on your two-wheeled adventures. They make riding those sections less frightening as well, so I’d rather have them than not.
Downsides
They do come with a slight weight penalty, about 120 g per wheel, but tyre sealant weighs more than a tube does anyway, so what are a few extra grams? Save a bit of that added weight by running a tyre with a less aggressive tread. In most cases, you may not even notice the difference.
Most would be happy to accept the initial installation frustration and the added weight for the positive trade-offs the inserts provide, that of security, improved speed and traction (especially in corners), their dampening suspension effect, reduced flats and potential damage to your bike or tyres.
They can’t prevent major catastrophes or freak accidents on the trail like a slashed sidewall but they reduce the chances of them happening. In rare cases when you need your backup tube, you’ll have to remove and stuff them in your pocket, backpack or wear them like our cycling ancestors did, in figure eight around the shoulders or diagonally across the chest.
There is a distinct learning curve with their installation. Think of it as when you were learning to install tubeless. The first few attempts were a challenge but then you got the hang of it. Expect a similar experience with foam inserts. They aren’t inexpensive either. Kits cost upwards of £/€/$150, but that’s close to the price of a couple of sets of quality tyres you may save thanks to their use. Replacing rims isn’t cheap either.
Two popular brands
CushCore and Vittoria Air-Liners are the two major players on the market. Foam inserts aren’t just for gravel. We mentioned their downhill mountain biking roots but they have become popular additions to any mountain biking application. They are compatible with any 29” tyre and rim bed widths from 1.9” to 4.0”.
Let’s not forget road and cyclo-cross bikes! Vittoria makes their Air-Liners in three sizes, S, M, and L for recommended road tyre widths of 25,28 and 30 mm with internal rim widths of 21, 23 and 26 mm. CushCore does not currently offer a road-specific product but their gravel version may work in some applications.
Conclusion
If you are ready for improved handling and traction, fear-free aggressive handling, even fewer flats, an overall improved ride experience, and the chance to find your low-pressure sweet spot without the dread of flatting, then adding foam tyre inserts to your tubeless setup is for you.
They aren’t carte blanche to get away with every tyre tragedy on the trail but they significantly improve the experience and handling when riding tubeless gravel and other bikes. No other upgrade to your gravel bike can make it that much more capable.
