Tire inserts (popularized by brands like CushCore and Vittoria's Air-Liner) are seeing increased adoption in gravel, and to a lesser extent, cyclocross riding. These products gained popularity first in use in mountain bike tires and have since expanded into other disciplines. As the adoption of tubeless tires has exploded, especially in off-road disciplines, so too has development increased of complementary products like tire sealant, specialty tubeless valves, and tire inserts.
Let's take a look at tire inserts, how they are intended to work, and how to decide if you should use tire inserts for your riding style.
How do tire inserts work?
The basic premise here is a claimed increase in rim protection, fewer flat tires, better handling, and ultimately, faster riding (because you can ride more aggressively) by adding a foam tire insert to your tubeless setup. CushCore, for example, claims a 50% reduction in impact force when using their product, compared with a tubeless tire with no insert. Some brands also claim "run flat" features, allowing you to ride out of the wilderness or finish a key race with a puncture.
Consider a traditional clincher bicycle tire, in which a separate inner tube sits inside the tire. In this setup, the inner tube is the airtight portion, the tire itself is not. The inflated inner tube pushes up against the tire sidewalls, providing some stiffness during cornering, and adds a measure of additional protection in case the rim bottoms out on an obstacle.
In a tubeless setup, there is no inner tube inside to perform these functions. Adding a tire insert protects the rim and supports the tire sidewalls, like an inner tube would, with the key advantage that a tire insert cannot go flat. An argument can also be presented that the use of tire inserts can reduce or eliminate "burping" - the brief loss of air that occurs when aggressive cornering temporarily pushes the tire bead away from the rim far enough to break the seal.
The desire for lower tire pressures
Many riders in all disciplines are interested in running lower tire pressures, for increased traction, grip, and cornering performance. The days of pumping up road tires to 120 PSI for "lower rolling resistance" are gone. Cyclocross riders in particular are intimately familiar with the improved handling that can come from lower tire pressure. There's a lower limit, however, at which point rim damage becomes more likely. For more on this topic, check out Helen Wyman's method for setting cyclocross tire pressure, which can be shockingly low for small, lightweight riders.
Adding a tire insert can provide some additional protection for the rim and wheel, even when the tire pressure is very low. For gravel riders, this might mean they can finish an event with a puncture that would otherwise be race-ending, for a cyclocross racer, it might mean the ability to reach the pits where a spare bike is available, or reduced burping when running very low tire pressures in wet, muddy conditions.
What about tubulars?
In a world in which tubeless tires dominate MTB, tubular cyclocross tires still remain the standard for cyclocross professionals, and enjoy wide adoption from enthusiast amateurs, too. Riders who want the very best handling still choose tubular cyclocross tires in 2024. If you're one of them, this discussion about tire inserts doesn't apply to you, because tubulars already allow the use of very low tire pressures, and in the event that you do bottom out a tubular setup, the tubular style rim is much less likely to be damaged compared with a tubeless rim.
Tubulars are still the gold standard in elite cyclocross, although high-end tubeless cyclocross tires, like the Challenge HTLR Team line, continue to make performance gains. If you're using tubeless for convenience but miss the low pressures possible with tubulars, tire inserts might be for you.
Installing and removing tubeless tire inserts
You should always refer to the manufacturer's instructions, but generally, you can count on tire inserts increasing tire install time and frustration level. Tight inserts must be pulled over the rim, then you must get the tire bead under the insert and into the channel in the center of the rim. Ever broken a plastic tire lever? You just might when you first install tire inserts! Be patient, get help from a friend, and watch the install videos provided by each brand for tips and tricks.
How about tire sealant? How about tubeless valves?
Tire inserts don't replace or eliminate the need to use a tire sealant. Modern tubeless-ready style rims and tires aren't airtight without the use of a liquid tire sealant like Stan's NoTubes, Orange Seal, or Caffelatex.
Also note that tire inserts typically come with their own presta valve. This is because the foam tire inserts can block the airflow in other valves. As with any other tubeless tire installation, check my tips for installing stubborn tubeless tires, and always use an air compressor with an inflator to simplify the entire process. Using an air compressor will save you gallons of sweat with a floor pump - it's like the "easy button" for seating stubborn tubeless tires.
Weight considerations?
Racers may have the weight of their bike, especially rotating weight added at the rim, at the top of mind. You'll need to carefully consider whether a weight penalty from tire inserts is offset by an opportunity to corner faster and more aggressively, or avoid race-ending mechanical failure (like in a long-distance gravel race.)
So how much do the inserts weigh?
- Vittoria Air-Liner Road, Size Large (for 700x30-32 tires) - 39 grams
- Vittoria Air-Liner Gravel, One Size (for 700x31-40 tires) - 47 grams
Big, strong riders who corner aggressively may be more interested in tire inserts compared with lightweight, cautious riders. Bigger riders can produce more watts to overcome any real or perceived weight disadvantage, and are more likely to face the challenges that tire inserts address.
What about compatibility?
Before adding tire inserts, carefully review the manufacturer's instructions and specifications. They come in multiple sizes, to match different width tires, and also are designed to match specific internal rim widths. Veer outside these guidelines, and you're going to have a hard time.
Key downsides of tire inserts
Any product has pros and cons. You may have seen photos of pro road teams on the side of the road with green tire inserts clearly visible inside a tubeless tire that blew off the rim, for example.
That being said, in professional races, where fractions of a second can mean winning or losing, at least some teams clearly think that the benefits of tire inserts more than offset the downsides. Here's what to expect when considering tire inserts for cyclocross or gravel bikes:
- Adds weight - about 1-2oz per wheel - less for narrow tires, but if you're running wider tires, expect more weight
- Some additional complexity at installation, initial setup of a new tire takes longer and it's more time consuming to swap between tires
- Expense - tire inserts can cost almost as much as some tires; for example: CushCore's Gravel / Cyclocross set of two inserts and valves carries a retail price of $150
Hit me up at @RideCX on Instagram, X, or Facebook and let me know if you're running tire inserts with tubeless for the 2024/25 season, I'm curious to hear your feedback.
Happy riding!