Vittoria Airliner Gravel © C. Lee / Cyclocross Magazine
Vittoria Air-Liner Gravel is one of the more popular tubeless tire inserts in the U.S. today thanks to its wide availability in North America. Our earlier installments of this tubeless tire insert review looked at a DIY option, as well as the Tannus Armour. We previously reviewed and found benefits from the Cushcore Gravel/CX insert. Inserts in a tubeless tire offer rim and tire protection from sharp strikes, tire bead retention, and some sidewall stability that allows confidence riding with lower tire pressure.
Arguably the first commercially available and successful tubeless tire insert is the Cushcore (the Schwalbe Procore system predates Cushcore but was not a commercial success). As intended by the founder, the original Cushcore stabilizes the tire sidewall to improve cornering while maximizing tire traction and cushion with lower tire pressure. It also provides rim protection by providing a cushioning layer over the rim and it fills the rim channel to aid tire bead retention. This is originally for mountain bike applications.
Other tire inserts have flooded the market. The meteoric rise of gravel riding means tires narrower than mountain-bike-size are fit to wide rims so the rim is vulnerable to trail damage. This adds new demand for tubeless tire inserts. The gravel cyclist wants the medium-sized tire to balance low rolling resistance on the pavement with the ability to ride confidently off-road. Lower tire pressure meets the need to gain traction and smooth the ride when off-road on these medium-diameter tires. For cyclocross, the demands on a tubeless clincher tire are quite similar, though encountering sharp rocks is less frequent. With the demands of gravel and cyclocross in mind, companies consider the priorities of rolling resistance, weight, protection, bead retention, and tire handling differently than with a mountain bike.
Air-Liner
Vittoria is a large cycling brand well established in the bicycle tire segment. They have great success with road and cyclocross tubular tires and clincher tires as well. Vittoria introduced the narrow tubeless Cross XL Pro clincher for cyclocross in 2013 when tubeless cyclocross clinchers were a new segment, then replaced that with the Terreno line of tubular and clinchers.
Vittoria’s resources and experience in the tire and wheel segment puts them in a good position to develop tubeless tire inserts. Vittoria now has tubeless tire inserts in each category of mountain, gravel/CX and road, with a slightly different performance emphasis for each.
Vittoria Air-Liner (l-r) Road, Gravel. © C. Lee / Cyclocross Magazine
We purchased our Air-Liner Gravel from a local bike shop for the MSRP of $40 for one wheel, but it is readily available from many sources. The liner is a 100mm long strip that the installer cuts to size. Included in the nice string bag package are a matching green zip-tie and a very nice side-opening Presta valve stem with a removable core.
The side and top opening valve stem are included with the Vittoria Air-Liner Gravel. © C. Lee/Cyclocross Magazine
The Vittoria Air-Liner Gravel is surprising in size, compared to other inserts in this series. It is diminutive with a 23mm maximal width and 15mm height. The Air-Liner Gravel is dense green EVA (ethylene-vinyl acetate) foam with a trapezoidal cross-section, the widest 23mm portion sits at the top and the narrow 17mm portion rounded fits into the rim. The 15mm height means it sits approximately 10mm higher than the rim wall of a typical tubeless gravel rim.
EVA foam has very similar properties to PE (polyethylene) foam and the application of each is nearly interchangeable, however, EVA has a smoother finish. Vittoria does not state a recommended rim width but does recommend a tire width of 31-40mm with the Air-Liner Gravel. Most gravel rims are 21-25mm internal width, appropriate with the tire sizes stated. For a 650B wheel, 47mm and wider tires are the most common for gravel riding and are outside Vittoria’s recommended parameters. A 650B wheel with a 47mm tire has approximately the same outer diameter as a 700C wheel with a 28mm tire.
Vittoria Airliner Gravel on a 21mm internal width rim. © C. Lee / Cyclocross Magazine
Preparation and Installation
Preparation and installation are similar to the penny-pinching DIY insert reviewed in Part 2. Wrap the un-cut insert around the rim and stretch in a bit while it is in the channel. Mark the length and cut to size with a razor knife. For 700C, the cut size is approximately 80cm. Poke a hole 2cm from each end from the rim side to the tire side and zip-tie the two ends together. Trim and tuck the end as much as possible into the hole, though due to the density of the EVA foam and the large zip-tie head, I could not bury it.
Vittoria Gravel Airliner is low profile EVA foam. © C. Lee / Cyclocross Magazine
Vittoria does not recommend notching the Air-Liner Gravel for the valve stem but does specify using the included side and top opening valve stem. The sized and cut Air-Liner Gravel is 40 grams before installing the zip-tie.
Installation was on the same wheel and tire setup as Parts 1 and 2 of this series, an old Bontrager Aeolus rim with a 21mm internal width and a WTB Raddler 700C X 40mm tire. The tire measures 39mm on this rim when inflated to 24 psi. I presumed the diminutive insert was certainly going to be easier to install than the other inserts. I pre-installed the tire and then dismounted one bead, leaving the other bead seated. I installed the Air-Liner Gravel like a tube. On the 21mm internal width rim, the Air-Liner Gravel fits well into the rim channel and is near the internal rim wall. You must compress and lift the insert slightly for the tire bead to fit into this combination. This tire has now been taken on and off the wheel several times and also ridden for a few hundred miles, so the bead is not as tight as a new tire. In this case, installing the bead was not difficult, but still requires pushing the bead below the insert well into the rim channel. For installation, I like helpful tools like the Cushcore Bead Dropper and the Kool Stop Tire Bead Jack. The former is useful to install and also remove tubeless tires when any insert is used.
To make installation easier with a new tire, I recommend installing the tire without an insert to stretch on a rim for a day. For this step, you can use an inner tube if the tire does not hold air without sealant. Vittoria also recommends wetting the Air-Liner Gravel to help it slip into the tire. On a wider rim, the Vittoria Air-Liner Gravel does not fit nearly as snug against the rim wall, so installation is easier. Seating the tire bead was not difficult with a compressor. Seating the bead with a standard floor pump is not likely with this combination now.
Vittoria AIrliner Gravel on a 25mm internal width rim (top) vs on a 21mm internal width rim (bottom). © C. Lee / Cyclocross Magazine
Add sealant through the valve stem with the core removed. This was not complicated with the large side and top openings of the included Vittoria Air-Liner valve stem. With air in the tire the sealant distributes well with the usual shaking and rotation.
Performance
I rode the same WTB Raddler 40 tire and Bontrager Aeolus wheel combination through this series of reviews. This burp-prone combination that I was most comfortable riding 22-24 psi on a front wheel in a standard tubeless setup, depending on road and trail conditions. For the sake of comparison and simplicity the review comments are primarily about this front wheel combination. I did try a mix of other wheel and tire combinations including wider rims and different tire sizes. For reference, the other tubeless tire inserts allow a 4mm psi drop while maintaining confidence in handling and wheel protection. I weigh 155 pounds. I rode the same roads and trails that have a good amount of Class 4 gravel. I also lapped a cyclocross loop with a more typical mix of sand, grass, roots and loam.
The Vittoria Air-Liner Gravel fits snugly into a 21mm internal rim, a narrow size for gravel-specific rims now, but still quite common for road rims that can fit gravel tires. The widest part of the Air-Liner Gravel is 23mm, about equal to the edges of the rim walls. On a 25mm rim, likely the widest rim used for a 40mm tire today, there is a 2mm gap on each side of the Air-Liner Gravel and the rim walls. This potentially gives less bead retention and rim wall protection, but tire beads are about 3mm wide so this difference is small.
The Air-Liner gravel cross-section very roughly calculates to fill 20% of the cross-section of a 39mm tire on ta 21mm wide rim. That is about 30% less than the amount of the other inserts in this series. Despite the small volume, the insert is palpable with the tire deflated. Compared to a tire without the insert, the deflated tire has more body and deforms less. Beginning with 20 psi and decreasing the tire pressure in 1 psi increments on my cyclocross test course, I began to lose cornering confidence around 17 psi. The tire felt floppy at 15 psi, but when completely flat, I rode over half the course without dismounting but cornering was sketchy. The tire bead did not unseat and I did not have the hard sensation of riding with the tire sidewall against the rim. This performance was surprising considering the much smaller volume of the Air-Liner Gravel than the other inserts.
For my square-edge impact test, I use a low curb. Performed repeatedly with decreasing tire pressure, the Air-Liner Gravel did its job damping the impact with no rim or tire damage even as I put in a mild sprint with a deflated tire. The tire did not burp or unseat. The Vittoria Air-Liner gravel does not instill the same run-flat confidence of the DIY insert, but it felt similar to the Tannus Armour, a bit better than riding on a flat tubular tire.
I briefly discussed rolling resistance and hysteresis with tire liners in the previous installment of this tire insert series. The Vittoria Air-Liner Gravel does not add to the resistance of deformation and rebound since it does not contact the tire sidewall very much. It therefore would not damp the sidewall flex during hard cornering as well as the Tannus or Cushcore. This comparison was hard to gauge subjectively when riding, but I did feel the Vittoria Air-Liner Gravel did its job allowing stable handling with lower pressure than without an insert. The performance parameters were similar to the other liners in this review series, which surprised me since the Air-Liner Gravel is so narrow and small. I thought the tire would feel floppier with declining tire pressure compared with the wider and larger inserts. This did not happen.
One benefit the small cross-section of the Air-Liner Gravel has is it coils into a small size in the event you have to replace it with a tube in the field. That’s a messy misfortune, and perhaps Vittoria includes the small reusable string bag as packaging so you can use it to carry the slimy serpent home. The small cross-section potentially allows insertion of a tube without removing the insert if you can place the cut section over the valve stem hole. It would work best with a tube that has a very long valve stem and is one size smaller than the tire. I have not yet tried this.
The Verdict
Vittoria’s Air-Liner Gravel is widely available in North America and checks all the tubeless tire insert boxes. It protects the rim, retains the bead, and provides some level of sidewall stability yielding more confidence to run low tire pressure for comfort, traction and control. The $40 USD (for one wheel) Air-Liner Gravel weighs 40 grams cut for 700C and comes complete with an excellent clog-free side opening removable core valve stem. The cost and performance of the Air-Liner Gravel are on par with the other inserts in the review series. When I compare the Vittoria Air-Liner Gravel to the other inserts, its advantage is lightweight and perhaps less effect on rolling resistance. The disadvantage is perhaps less ultimate rim protection and run-flat capability.
The 40mm is the maximum tire width recommended by Vittoria for the Air-Liner Gravel, which is now medium-sized for gravel riding. Routinely 42mm tires on 25mm internal rims are winning major gravel events. It will be interesting to see if Vittoria decides to offer a larger size for the Air-Liner Gravel. The tire size recommendation for the Air-Liner Gravel is too small for the most common 650B gravel tire sizes. The smallest Air-Liner Mountain has a minimum 1.9 inch (48mm) tire width recommendation. The lightweight and small diameter make the Air-Liner Gravel ideal for cyclocross racing and maybe I’ll buy another for the upcoming season.
Stay tuned for Part Four, revisiting the Cushcore insert.
Vittoria Air-Liner Gravel Tubeless Tire Insert Specs:
MSRP: $40 per wheel, includes valve stem
Size: Cut to size. 31-40mm tire size
Weight: 40 grams per insert as tested (cut).
Warranty: not stated, see company website
More info: Vittoria.com
