I feel a bit like Batman incognito as I lift the bike with the futuristic X-Sense carbon rim out of the car. A few bikers standing around give me furtive glances. One of them is fidgeting. "Are those prototypes?" he finally asks. "No," I reply, "they're already available."
You will find these four wheel concepts in the test:
- Notubes ZTR Bravo Team
- Alchemist X-Sense 7.33
- Kuroshiro Enso 747 / Tune Skyline
- AX-Lightness Enduro 27.5C
Welcome to the future!
When bike manufacturers discovered carbon fibre composites, or carbon for short, as a frame material, the frames were virtually identical in design to their aluminium counterparts. Today, the special material properties of carbon are better utilised and manufacturing processes have been mastered that seem to know no bounds. Anyone who looks at the complex shapes of modern fully frames knows what we are talking about. The same development could be in store for rims. So far, it seems that only the materials have been changed - what was previously made of shiny silver light metal is now made of carbon. If you buy a high-end carbon rim today, you can hardly tell the difference between it and its aluminium counterpart. Lighter, stiffer and more expensive, but otherwise almost identical. And this despite two manufacturing processes that could hardly be more different (see below).
But things are slowly starting to move. The first resourceful developers are beginning to ask whether the possibilities offered by carbon fibre - free from previous conventions - can be used to build even better rims. We took a look at four new rim designs. The spectrum ranges from a Notubes ZTR Bravo, which integrates vertical flex into its hollow chamber construction, to bizarre-looking designs such as the Alchemist X-Sense, which almost seems to have been borrowed from science fiction. With all four test candidates and their futuristic high-tech constructions, the manufacturers are breaking new ground. All of them utilise the design possibilities of carbon to an unprecedented level. Innovatively different, but unfortunately also wickedly expensive. In order to find out whether, in addition to a lighter account, they also bring tangible benefits and whether even Batman would approve of them, we thoroughly tested them both in the lab and on the trail.
RIM SHAPES AND MANUFACTURERS
The classic aluminium hollow chamber rim has been the predominant basic shape for decades and still clearly dominates carbon rims today. But there are other options. The Kuroshiro Enso 747, for example, is a wide single-wall rim that gets its high rigidity from the small, zigzag-shaped channel. The hollow chamber is reduced to an absolute minimum here. On the AX-Lightness Enduro, the large centre channel is covered by a 0.2 mm (!) thick carbon layer. The wide shoulders have a flexible design. The Alchemist X-Sense utilises the design potential of the material to an even greater extent. Its trapezoidal hollow chamber is asymmetrical, and the spoke holes are outsourced to small side ledges for an airtight rim bed. Striking: the extremely large differences in wall thickness of the last two models, which are intended to give the rims the ability to react slightly elastically to hard impacts.
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INNOVATIVE WHEEL CONCEPTS PUT TO THE TEST
We tested the four most exciting rim designs in the form of complete wheelsets in the lab and on the trail. The results surprised even us.
Notubes ZTR Bravo Team (Trail to Enduro, 29")
Although it is still a hollow chamber rim, the Bravo with its rounded rectangular cross-section and customised carbon layup aims to be more than just torsionally rigid. The RiACT technology is designed to cushion load peaks. With a vertical deformability of up to ten millimetres, the rim should be able to withstand higher loads, protect the tyre from punctures and at the same time ride more comfortably. In practice, you can tell that tubeless experts were at work on the ZTR Bravo - tyre fitting and inflation are easy. The large rim width of the hookless rim also guides wide tyres cleanly. On the trail, the classically constructed wheelset is really stiff and smooth. It is impossible to say whether this is due to RiACT or the carbon-typical inherent damping. Not cheap, but by far the cheapest set in the group.
- Exemplary tyre fitting and inflation
- Decently stiff and precise handling
- Subjectively quite comfortable when riding hard
- Cleanly constructed trail to enduro wheelset for a wide range of applications.
Price / Info 1699 Euro / www.notubes.com
Total weight (VR / HR) 1708 g (790 g / 918 g)
Width (outside / inside) 32 mm / 26 mm
Material UD Carbon
Tyre width recommendation 2.0 to 2.5"
Field of application Trail to Enduro
Components / Construction
Hubs Notubes Neo
Spokes / nipples Sapim Race / Sapim Alu
Construction 28 spokes / triple crossed
Rider weight / air pressure (max) 113 kg / 2.6 bar
Measurements
Stiffness (VR / HR) 63 / 50 N/mm
Inertia (VR / HR) 479 / 512 kg/cm²
Remarks Carbon hollow chamber construction with flex-optimised profile (RiAct), hookless, also 27.5 and 26"
Torsionally stiff and precise on the trail, yet resilient and comfortable - the rectangular cross-section and the special carbon construction should make this possible. The 3 mm wide, hookless rim flanges increase stability and prevent defects in the carcass, for example due to hard punctures.
Alchemist X-Sense 7.33 (Enduro, 27.5")
The most important feature of the futuristic design are the two side ledges in which the spoke nipples are located. Thanks to this design, the wide rim base has no spoke holes, which is why the X-Sense can be used as a genuine tubeless rim. In addition, the tyre can simply remain mounted when replacing a spoke. Due to the high tensile loads, each nipple hole is additionally stabilised by adapted hollow chamber cross-sections. The wheelset is light, but not the lightest. Nevertheless, its low rim weight makes it easy to accelerate. The X-Sense rim itself is stiff. However, the wheel stiffness is not optimal due to the special spoking.
- Futuristic look and highly innovative design concept
- Top acceleration thanks to lightweight rims
- Clean construction with even spoke tension, but only 24 spokes
- Only moderate lateral stiffness (especially at the front)
Price / Info 2400 Euro / www.shock-therapy.de
Total weight (VR / HR / rim) 1550 g ( 698 g / 852 g / 450 g)
Width (outside / inside) 38 mm / 32.8 mm
Material UD Carbon
Tyre width recommendation 2.0 to 2.8"
Field of application Trail to Enduro
Components / Construction
Hubs Alchemist Stealth
Spokes / nipples Sapim Race / Sapim Alu with washers
Construction 24 spokes / double crossed
Rider weight / air pressure (max) 113 kg / 2.6 bar
Measurements
Stiffness (VR / HR) 45 /40 N/mm
Inertia (VR /HR) 389 / 412 kg/cm²
Remarks Complex hollow chamber T-profile with external spoke holes, tubeless
Thanks to the complex design of the X-Sense, the spokes and nipples are freely accessible on the outside. The rim base without spoke holes is airtight.
Kuroshiro Enso 747 / Tune Skyline (CC to Trail, 27.5" Plus)
Sometimes it just has to be light. With its 36 mm rim width, the Kuroshiro Enso 747 is the narrowest version of the Enso rim family. Like its fatbike siblings, it has a single-wall construction. However, in order to achieve the necessary stiffness, the zigzag groove in the rim bed is additionally covered with a thin layer of carbon, as a mini hollow chamber, so to speak. Thanks to a special trick, the weight of the sealing tape can also be saved: Because the special Sapim aluminium nipples sit precisely in the spoke holes, the rim is airtight even with sealing milk alone. At just 350 grams (front wheel version) and 400 grams at the rear, the Enso is extremely light for its width and has good lateral stiffness. However, it has very conservative weight and tyre pressure limits. Maximum lightweight construction for plus bikes.
- Very light, quick to accelerate, reasonably stiff
- Sealing of spoke holes unproblematic (Notubes sealant recommended), but difficult to inflate tubeless because the zigzag groove allows air to escape sideways.
- Even for plus low weight and pressure limits
Price / Info 2590 Euro / www.tune.de
Total weight (VR / HR / rim) 1418 g ( 650 / 768 g / 350 g / 400 g)
Width (outside / inside) 45 mm / 38.6 mm
Material 18 k UD Carbon
Tyre width recommendation 2.6 to 3.25"
Field of application Plus bikes - CC to Trail
Components / Construction
Hubs Tune King & Kong Boost
Spokes / nipples Sapim D-Light / Sapim Polyax Alu
Construction 32 spokes / triple crossed
Rider weight / air pressure (max) 91 kg / 1.2 bar
Measurements
Stiffness (VR / HR) 56 / 48 N/mm
Inertia (VR / HR) 362 / 378 kg/cm²
Remarks Single-wall construction with mini hollow chamber, also in 29" and Fatbike, tubeless-ready
In its basic principle of a single-walled rim, the Enso 747 utilises a zigzag groove for reinforcement. The nipple holes are also embedded in this groove. With special aluminium nipples, the rim is airtight even without sealing tape using only sealing milk.
AX-Lightness Enduro 27.5C (Enduro, 27.5")
An enduro rim for lightweight construction freaks? Yes, and what a rim! The most important feature of the design is that the rim shoulders, which protrude far beyond the central hollow chamber, can flex under impact loads. This prevents overloading and reduces the impact energy in the rim. To prevent tyre damage, the hookless rim flanges are also extremely wide (6 mm) and almost round at the top. The principle works on the trail. It ensures that the tyre stays firmly on the ground and noticeably absorbs impacts. While the front wheel is quite stiff, the rear wheel lags far behind despite the Boost. However, the lack of lateral stiffness on the test bench is hardly noticeable on the trail. The rim shoulders are extremely high for a bombproof tyre fit. As a result, the tyres only settle close to the maximum pressure, even with mounting paste (see problem cases box).
- Direct ride feel with a firm ground position and high subjective comfort
- Very light for enduro use
- The very wide and round sidewalls prevent snakebites and offer high impact protection
- Critically tight tyre fit
Price / Info 2790 Euro / www.ax-lightness.de
Total weight (VR / HR / rim) 1486 g ( 687 g / 799 g / approx. 430 g)
Width (outside / inside) 46 mm / 36 mm
Material 3 k carbon braiding
Tyre width recommendation 2.35 to 2.5"
Field of application Enduro
Components / Construction
Hubs Extralite Hyper Boost
Spokes / nipples Sapim D-Light / Sapim Alu
Construction 32 sp. / 3-fold crowned (f. r. radial)
Rider weight / air pressure (max) 100 kg / 2.5 bar
Measurements
Stiffness (VR / HR) 56 / 38 N/mm
Inertia (VR / HR) 441 /457 kg/cm²
Remarks Hybrid single wall/hollow chamber with pre-laminated spoke holes, hookless, only 27.5", flexing rim
The AX-Lightness Enduro is built in such a way that the rim shoulders can deflect independently of the stiff centre groove in the event of impacts and thus dampen load peaks. This provides comfort and stability reserves.
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PROBLEMS
All designs are trend-setting, but in some respects also extreme. So it's not surprising that not only positive effects occur in everyday cycling.
Kuroshiro Enso 747
Sealing without tape works perfectly. Unfortunately, a lot of air escapes between the tyre bead and the rim at the corners of the channel. Tubeless inflation is very difficult without a compressor.
Alchemist X-Sense 7.33
Weak point spoking: With only 24 spokes, the X-Sense wheel is already close to its limit. However, because the spokes also cross over each other unfavourably, stiffness suffers.
AX-Lightness
Very high rim shoulders generate extreme stresses during tyre fitting. A rim weakened by a manufacturing defect cracked during tyre fitting! However, the replacement rim held without any problems.
CONCLUSION Christian Artmann, BIKE tester
It is always exciting to take a look at products at the limit of what is currently possible. Especially because up to now, everything to do with rims has centred on weight and maximum stiffness. The manufacturers' wealth of ideas and willingness to innovate are remarkable. The continuing trend towards wide rims is very pleasing. I also think the concept of limited flexibility as a stability reserve or for comfort and airtight rims without tape is great.
However, it is also clear that innovations are often accompanied by compromises - be it in terms of weight limits, handling or wheel stiffness. The fact that the Notubes ZTR Bravo, as the most conservative wheel concept in the group, has the least compromises shows that the hollow chamber construction is far from being a thing of the past - carbon or not. Due to the exclusive prices, the innovative wheels on show will remain pure tuning dreams for most of us for the time being anyway.
What's more, despite all the excitement about innovations, it should not be forgotten that the choice of tyres and the optimum tyre pressure have a much greater influence on handling, comfort and acceleration than the rims.
