A Guide to Hookless Rim Technology

Hookless rim technology is becoming increasingly popular in the construction of road wheels yet it isn’t new, it was first developed for mountain bikes. The reasons for its development were driven by 3 major advantages it could provide:

  • Increased rim wall strength and durability
  • Lower weight
  • A better seal between the tyre and the rim

This technology can now be found in many road and gravel wheels, including the CADEX wheelsystems, which are constructed using very lightweight but also very strong carbon fibre. This technology offers the same advantages as mentioned above and more. Here we’ll take a look at what exactly Hookless rim technology is and the benefits it brings.

Hooked Vs Hookless

A traditional hooked rim has a groove running along the inside edge of each sidewall of the rim which is where the bead of the tyre sits to hold it onto the rim. This groove is, however, a weak spot as it is, in most cases, the thinnest part of the rim and therefore needs to be reinforced with extra material which adds weight and width to the rim.

A hookless rim does not have these grooves so the side walls are smooth inside and out. By not having this groove in the rim, the rim is stronger and more durable as the weak spot has been eliminated. Furthermore, it doesn’t need any additional reinforcing which is why hookless wheels are both stronger and lighter. This also extends to the tyre itself, as a hookless system allows for a smaller, lighter tyre to have the same volume as a larger, heavier tyre, resulting in a lighter overall weight.

Saving weight in the rim is arguably the best place to save weight on a bike as it’s rotating weight which effectively gets heavier as the wheel spins faster.

As mentioned above, hookless wheels offer a better seal between the rim and tyre. This improved seal comes from the shape of the bead of the tubeless tyre (which must be used with a hookless rim) which is different to that of a regular, clincher tyre. With a hookless rim there is complete contact between the tyre and the rim in this critical area; a better seal means less air loss and also, under extreme cornering, the chance of the tyre “burping” the wheel is virtually removed.

Burping usually happens in a corner and occurs when the side force on the tyre is so great that for a split second the seal between the tyre and the rim can be broken and air can escape. In order to prevent this further, rather than using a Kevlar-only bead, which can stretch over time and compromise the tyre bead diameter, Cadex tyres feature a carbon and Kevlar composite bead that’s strong enough to avoid stretching under heavy loads.

This, combined with our accurately defined tyre and rim bead seat diameters, tested at pressures up to 150psi, guarantee dependable air and tyre retention.

Hookless rims also help create a more round tyre shape that provides superior grip and handling as well as added sidewall support when cornering meaning more confident handling for the rider.

An additional advantage that a hookless road wheel can offer is improved aerodynamics. The side walls on a Cadex hookless rim are only 2mm thick whereas on a traditional hooked rim the width can be over 5mm in some cases. Thick rim walls can create a ‘pinch point’ in the air flow as the air passes over the tyre and the rim which creates turbulence. This ‘pinch point’ can be compared to the middle of an hourglass and by reducing this ‘pinch’ (ie. by having thinner rim walls) makes for a straighter tyre and rim profile which results in smoother air flow and improved aerodynamics.

A second benefit of the thinner rim walls is that the inner width of the rim can be much greater when compared to the outer rim. Wider tyres are being much more regularly used on road bikes with thinner tyres being used less though they are still ideal with certain rim widths to aid the aerodynamic properties.

The standard on road race bikes is now commonly thought of as 25mm, with many riders seeing the benefits of going even wider to 28mm and beyond. Wider tyres need wider inner rim widths to give the tyre more support especially while cornering. A Cadex 42mm wheel for example has an internal rim width of 19mm with an outer width of just 23mm. On a hooked rim the outer width could be 27mm+, which adds a lot of weight in this critical area.

While a hookless rim does offer many advantages, some people may consider one restriction of a hookless rim is that it must be used with a tubeless tyre. However, this in itself comes with its own benefits:

  • Lighter weight as no inner tube
  • Lower tyre pressures as no inner tube to pinch puncture
  • Greater grip from lower tyre pressure
  • Improved comfort again from lower pressures
  • Dramatically reduced risk of punctures (especially pinch flats)

Although the rims are tubeless tyre dedicated, you can still fit an inner tube into an approved tyre if you puncture out on the road to get you home but this shouldn’t be a long term solution. You can find out more about tubeless technology by visiting our guide here.

To summarise, Cadex hookless technology offers rims that are lighter, stronger, more durable, more aerodynamic, offer better tyre support and a better air seal compared to a hooked rim. It is worth noting that as there is no ‘hook’ or groove, the way that the tyre’s bead is made is critical and because of this not all tubeless road tyres are compatible.

Find out more about hookless technology here.