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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.
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.
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.
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.
Incredible low weight, but can be delicate, especially during installation
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road.cc test report
Make and model: Tubolito S-TUBO CX/GRAVEL
Size tested: 700x30-47mm Presta 60mm
Tell us what the product is for and who it's aimed at. What do the manufacturers say about it? How does that compare to your own feelings about it?
Tubolito says: 'Not only spare: developed to fit in any small pocket, 35 grams lightweight S-Tubo-CX/Gravel All due to its very small packed size is the ideal spare tube for all 700c and 650B tires from 30mm-47mm width. However, it is not only a savior in need but can be perfectly used on a daily basis as it still is as robust as standard rubber tubes. Also leftovers of tubeless liquids do not do any harm to it. Given its low rolling resistance it can also become the decisive advantage at competitions. Available with 42mm (35 grams) and 60mm (36 grams) Presta valves and suitable for disc brakes.'
Tell us some more about the technical aspects of the product?
Perfect CX/Gravel spare tube
Can also be used as daily driver
Lightest CX/Gravel tubes worldwide
Can be used in 700c and 650B tyres
Compatible with disk brakes
Same strength as a standard tube
Low rolling resistance
perfect spare tube for tubeless setups
Tell us how the product performed overall when used for its designed purpose
Installation is tricky, especially if you have tight tolerance between tyre and rim, but once on it delivers a good ride quality and it's incredibly light. I might just have been unlucky but I did experience a few punctures, which made me constantly worried about it potentially failing.
Tell us what you particularly liked about the product
Incredibly low weight and low pack size.
Tell us what you particularly disliked about the product
Hard to install and while patching is possible, it is not easy or quick.
How does the price compare to that of similar products in the market, including ones recently tested on road.cc?
Schwalbe makes an Aerothan version for 37-50mm tyres at £24.99, although this is more a comparison to the standard Tubolito version, not the S-Tubo. Pirelli makes the SmarTUBE Cinturato, which is for 33-45mm tyres, for £27.99, with a claimed weight of 49g.
Did you enjoy using the product? Mixed. It felt good while riding, but an early puncture and the difficulty installing it meant I was always conscious of the inner tube and worried about it failing.
Would you consider buying the product? Probably not.
Would you recommend the product to a friend? I would recommend the standard version over the S-Tubo version, especially for off-road use.
Use this box to explain your overall score
The ride quality is good and the weight is unbelievable, but it's harder to install than butyl, and while the low volume is good, there are potential issues if it were to be used as a sole spare.
About the tester
I usually ride: My best bike is: Cannondale SystemSix
I've been riding for: Over 20 years I ride: Every day I would class myself as: Expert
I regularly do the following types of riding: road racing, cyclo cross, sportives, mtb, Lots of gravel style riding
Matt is an endurance nut who loves big rides and big events. He's a former full-time racer and 24hr event specialist, but now is also happy riding off-road on gravel bikes or XC mountain bikes and exploring the mountains and hills of Mid Wales.