Tubolito S-Tubo CX/Gravel inner tube

At 33g, the Tubolito S-Tubo CX/Gravel is an insanely light thermoplastic inner tube designed for off-road use with 30-47mm tyres in both 650B and 700C wheel sizes. The tubes are absolutely tiny, taking up minimal space in a pocket or bag, but there are a few factors, including time to patch, that make me hesitant about using one as a sole spare.

Thermoplastic (TPU) inner tubes have been gaining popularity over the last few years, with claims of increased strength over latex or butyl inner tubes, gram for gram. Tubolito makes two versions designed for cyclo-cross or gravel bikes, for 650B or 700C wheels and tyre sizes from 30mm to 47mm. I've been testing both the non-S Tubo CX/Gravel and this S-Tubo, which is lighter, weighing an incredible 33g.

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The S stands for spare, and while the tube can be used for more general day-to-day use, the very low volume and light weight might make it a standout option where you have limited space.

The inner tube is incredibly thin, and – as with the non-S – I recommend taking your time when installing it, as the material can easily catch between the tyre bead and the rim. If you have a setup that is already tight and installing a tyre is hard, even more care is needed.

Installation is a little different to standard, as Tubolito recommends pre-inflating the tube to give it shape, to help. I recommend not using tyre levers either, as it will be very easy to tear the material if it gets caught.

Although designed for off-road use, the tubes could also suit road bikes with wider (30mm+) tyres and initially this is how I tested them.

The first ride was far from perfect, puncturing after just 5km on the road. While this may have just been bad luck, it put doubts in my mind for future rides.

I did repair the tube that punctured, later, using the Tubolito patch kit (also being reviewed – up soon), and it worked, but it takes much longer than repairing a butyl tube with a vulcanised rubber patch, needing 30 minutes to dry. I also found some constant pressure needed, so I suggest doing this at home.

I have spent many more miles testing both the patched version and a new one, on road rides and off-roading, and one noticeable difference is the ride quality compared to a butyl tube. This is something I also found when testing the Schwalbe Aerothan TPU tube.

The Tubolito S-Tubo is claimed to be as strong as a butyl tube, though just a fraction of the weight. In comparison, a butyl inner tube designed for similar sized tyres will weigh 120-170g and also take up more space.

Using the S-Tubo as a spare throws up a few potential issues – I wouldn't carry it as my sole spare tube. There's the extra time it takes to install, and how easy it is to puncture should you catch the tube when installing. Also, should you have to use it and then be unfortunate enough to puncture again, there's the time it'll take to fix and the requirement to take a specific fixing kit, reducing the benefits further.

Compared with either an inner tube or tubeless setup, the S-Tubo tubes will be significantly lighter, and although the ride quality is good, the same is true of a good tubeless system. A tubeless setup also offers better puncture resistance and allow repairs on the go with tubeless plugs.

> 9 things they don’t tell you about tubeless tyres

If you're completely set on inner tubes, these are almost certainly the lightest you will find for the wheel/tyre size, but I'm not convinced the 28g saved over the standard Tubolito is worth it. Both offer low volume, but the standard version has stood up to some incredibly rough riding terrain, whereas the S-Tubo has punctured a few times now, including that early one on the road.

Given the likely risk of punctures is lower on the road than off, it's certainly better as a road-only spare or main tube, for 30mm+ tyres, rather than for off-road use.

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At £29.99 each, they are expensive compared with butyl inner tubes, although when considering price per gram, it's better value than some weight-saving upgrades.

They're a little pricier than other TPU inner tubes, too, but no other brand currently offers a version as light to suit gravel or cyclo-cross bikes.

Schwalbe's Aerothan is £24.99 and Pirelli's SmarTube is £27.99 for versions to suit gravel tyre sizes. 

TPU tubes have some real benefits over other inner tubes, especially in terms of weight and size, but for off-road use with gravel bikes, in particular, a good tubeless system should provide more puncture resistance and an equally good ride. It makes some sense as a small volume spare, at a cost, though for me it would be as a second spare tube.

Verdict

Incredible low weight, but can be delicate, especially during installation