The benefits of hookless rims are vague – so what’s the point of them?

Hookless rims have been back under the spotlight in recent weeks, with high-profile people within the industry questioning their safety and performance credentials.

Given this, I spoke to several key brands and figures within the bike industry, to cut through the noise and separate fact from hyperbole.

Previously, I dealt with the thorny question of whether hookless rims are safe for road bikes, where and why issues can arise, and what riders can do to minimise their chances of something going wrong.

In this second instalment (be sure to check out part one), I explore whether the claimed advantages of hookless rims stand up to scrutiny.

Proponents claim they offer improved performance in a number of key areas, and reduce manufacturing complexity and cost, but not everyone is convinced.

And if the limitations imposed by hookless rims aren’t countered by sufficient benefits, many riders will rightly question their utility.

Are hookless rims faster than hooked ones?

For many riders, it’s speed that dominates the conversation when it comes to wheels.

Carbon wheels with deep-section rims are typically prized for their ability to help you ride a bit faster, especially among road cyclists.

Unsurprisingly, part of the pitch for hookless rims has always been that they can potentially help you ride faster.

Zipp, for example, claims its hookless 454 NSW wheelset is 10 watts more efficient at 40kph than the previous hooked version from 2020, thanks to a combination of aerodynamic, rolling resistance, weight gains and reduced vibrational losses.

The American brand groups these four factors together under the umbrella term ‘Total System Efficiency’, or TSE, and says it offers a more holistic approach to performance in the real world, compared to simply comparing wheelsets in a wind tunnel.

Let’s go through each of the key claims, from reduced weight to improved aerodynamic performance, lower rolling resistance, and reduced cost and complexity.

Are hookless rims lighter?

The potential for hookless rims to be lighter is obvious – all else being equal, removing material tends to make something lighter, after all.

The claimed extent of such savings varies significantly, however.

Zipp points to a difference of 457g between its hookless 2021 454 NSW wheelset and the previous hooked version. This encompasses changes made across the entire wheelset, however, rather than simply the removal of bead hooks.

In contrast, when Hunt launched its 32 Aerodynamicist wheelset back in 2022, it noted the weight saved from a lack of bead hooks alone amounted to only “18g per rim”.

That’s not nothing, but it’s also fair to say 18g per rim isn’t going to transform anyone’s performance on the bike.

Somewhat ironically, the 'micro-hooked' rims on ENVE’s new SES 4.5 Pro wheelset are also claimed to save '10 to 15g' compared to the brand’s previous hookless rims.

Jake Pantone, ENVE's vice president of product and brand, explained that the brand’s original hookless rims were lighter, but the “thin (less than 3mm-wide) beads [the rim flanks] exacerbated pinch flats”.

To solve that issue, the brand created its Wide Hookless Bead, which helped spread the energy from impacts across a wider area, reducing the likelihood of pinch flats.

Roval’s latest Rapide CLX III and CLX Sprint wheelsets also feature similarly wide rim walls (albeit with bead hooks), which the brand calls FlatStop bead hooks.

Unfortunately, though, Pantone noted “this [Wide Hookless Bead] added weight back”.

With the new SES 4.5 Pro wheels, removing material from the lower internal part of that rim sidewall reduced weight again – and conveniently added back in the bead hooks.

So, all else being equal, are hookless rims lighter? 

As far as I can tell, the answer is “it depends”. But either way, we’re talking about tiny differences that are unlikely to impact performance in the real world.

Can hooked rims reduce rolling resistance?

Hookless rims might not be significantly lighter, but rolling resistance is more important when it comes to performance in most real-world situations.

For example, Zipp, claims the wider and shorter tyre contact patch created by its wider hookless rims compared to its older, narrower, hooked rims, helps reduce rolling resistance.

Zipp digs into this further in a white paper on its 'Total System Efficiency' philosophy, showing a 3.5-watt reduction in rolling resistance at 40kph with its hookless 303 S versus its hooked 303 Firecrest wheels.

According to Zipp, this is based on 'real world' testing by a third-party consultant.

With my sceptic’s hat on, this claim feels similar to its one regarding weight – which conflates a number of different changes and credits them all to ‘hookless rims’.

If its illustration showing the differing contact patches between its older hooked rims and newer hookless rims is accurate, Zipp isn’t comparing apples to apples.

After all, as we’ve seen with most road bike wheelsets in recent years, it’s perfectly possible to have hooked rims with a greater internal width, too.

Reserve wheels – which are used by Jonas Vingegaard and his Visma-Lease a Bike teammates – feature hooked rims with internal widths similar to those of Zipp hookless rims.

Nevertheless, Hunt’s senior development engineer, Patrick Brown, told BikeRadar its flagship SUB50 Limitless wheelset has hookless rims because testing by Vittoria showed they reduce rolling resistance by “one per cent” compared to hooked rims.

Brown suggested this is because the lack of hooks reduces “interference” with the tyres. 

While that may sound far-fetched at a glance, it’s not conceptually dissimilar to the way latex or TPU inner tubes can reduce rolling resistance by reducing the friction between the tyre and tube, compared to butyl tubes.

According to Brown, this figure came from testing on Vittoria’s own rolling resistance test rig, which is similar to the one found at the Silverstone Sports Engineering Hub, in the UK.

I contacted Vittoria to confirm this claim, but have not yet received a response.

Brown acknowledged this is a “marginal gain” but noted the SUB50 Limitless wheelset is pitched at riders seeking the best possible performance, and Hunt therefore didn’t want to leave anything on the table.

On the other hand, testing by Bicyclerollingresistance.com didn’t find any significant difference in rolling resistance between hooked and hookless rims.

Testing 28, 30 and 32mm-wide Continental GP5000 S tyres on hooked aluminium, hooked carbon and hookless carbon rims of similar widths, at various tyre pressures, the German lab concluded “hookless rims do not perform measurably better or worse than hooked rims”.

As with weight then, it seems there’s unlikely to be any significant advantage to rolling resistance when rims are equalised for things such as internal width.

The claim that hookless rims can reduce 'interference' with tyres sounds promising, especially because a one per cent improvement would be an appreciable gain. Without knowing exactly how this figure was derived, though, it’s hard to take it at face value when other tests don’t corroborate it.

The impact of tyre and pressure limitations

Beyond questions of whether bead hooks affect rolling resistance, another issue is how the limitations imposed by hookless rims affect what tyres riders can use.

AeroCoach’s Dr Xavier Disley points out that “tyre choice is so important, not just from a performance and speed standpoint, but also grip, puncture protection, etc. So limiting your customers’ tyre selection is a poor strategy”.

This was arguably more of an issue in the early days of hookless rims, where the fastest road bike tyres available simply weren’t compatible with hookless rims.

Nowadays, most of the best road bike tyres are hookless-compatible, so this might seem like a non-issue.

However, the size and pressure limitations imposed by hookless rims can still force riders to opt for a sub-optimal setup from a performance perspective.

Because of this, Josh Poertner, CEO of Silca, a former technical director at Zipp and consultant to a number of professional cycling teams, says he feels that hookless rims have “zero performance advantages”.

Citing his ‘rule of 105’ – which states a rim’s external width should be at least 105 per cent of the inflated tyre width for optimal aerodynamic performance – Poertner says riders will often need to use a wider tyre than is ideal for a given rim, in order to stay within the prescribed pressure limitations.

Disley cautions that the relationship between tyre and rim width isn’t as simple as that, however.

According to his testing, “there is no relationship between the external width of a tyre and rim and the overall aerodynamic performance of the wheel”.

A recent wind tunnel test comparing nine wheels, each fitted with a 28mm-wide tyre, for example, showed a combination with a rim-to-tyre-width ratio of 93 per cent performed better than some with much wider rims.

This is because “modern rims come in a range of shapes which vary in terms of their aero performance due to a number of factors, not just external rim width”, says Disley.

Regardless of the tyre-width conundrum, tyre and pressure limitations have long been a key issue in this discussion.

Having to compromise on tyre setup – whether in terms of model, size or pressure – has always felt like a non-starter, because it seems almost certain that the downsides of such a compromise would outweigh anything gained from your rims being hookless.

This is especially an issue for heavier riders, who are more likely to butt up against the pressure limitations of hookless rims. Many will need to use larger tyres that could weigh more and be less aerodynamic, instead of simply running slightly higher tyre pressures.

After all, despite weighing only 65-66kg, most online calculators recommend I use tyre pressures of around 60-65psi / 4.2-4.5 BAR in 28mm-wide tyres on 23mm-wide rims. That's only 7.5-12.5psi off the ETRTO- and ISO-determined limit of 72.5psi / 5 BAR.

Are hookless rims more aerodynamic?

Counter to Poertner’s claim that hookless rims may lead to a less aerodynamic setup, certain brands producing such rims claim the opposite.

Both Zipp and Cadex, for example, suggest the smoother interface between the tyre and the rim wall on hookless rims compared to hooked ones can reduce turbulence, and therefore aerodynamic drag.

On its website, Zipp says: “Without the hooked section of the sidewall, the transition from the rim to the tyre is streamlined, helping airflow to stay attached.”

Zipp's Total System Efficiency white paper shows a measurable difference in aerodynamic drag between its hookless 303 S wheelset and the old hooked 303 Firecrest, which is claimed to offer a 10.4W reduction in 'aero power' at 40kph (per the below table).

As with weight and rolling resistance, though, the changes between those two wheelsets encompass more than simply removing the bead hooks, so it's not conclusive that this improvement is due solely to that change.

In contrast, AeroCoach says it recently tested this theory in a wind tunnel, during the development of its new Thunderbolt tri-spoke wheel.

Comparing “both a hooked and hookless version of the wheel”, with the same tyre, showed “no aerodynamic performance improvement with hookless”.

Over a spread of yaw angles from 0 to 15 degrees, AeroCoach’s data shows a difference of only 0.1W in favour of the hooked rim at 45kph.

Of course, that’s only one wheel and tyre combination, and isn’t representative of every possible combination.

However, Poertner – who has run countless wind-tunnel tests with pro teams and athletes – says he’s “never once seen it to be true in an actual wind tunnel doing actual testing”.

Tim Jürgensen, head of engineering at Newmen wheels, told BikeRadar that “based on CFD simulations and wind tunnel testing, we cannot confirm any aerodynamic benefits of hookless rims with the common road tyres available today”.

Jürgensen also noted that as tyres get wider, “you need increasingly wide rim flanges” to aerodynamically optimise the wheel and tyre system, and “in this respect, the hook is actually beneficial and reduces drag”.

Are hookless rims cheaper or easier to manufacture?

One of Poertner’s main criticisms of hookless rims is his contention that “[wheel] manufacturers came up with hookless because it saves them money when they make the rims”.

That’s a sentiment shared among many of our readers, with countless comments claiming hookless rims were popularised by manufacturers for the sole reason that they’re easier and cheaper to produce.

Curiously, though, this isn’t something I can find many wheel manufacturers claiming explicitly.

Zipp, Giant and ENVE, for example, say the manufacturing process for hookless rims is better because it enables them to make stronger and more precisely sized rims, not because it's cheaper.

ENVE’s Jake Pantone says cost wasn’t a factor in the brand’s decision to switch to hookless rims.

“When we first introduced tubeless, we were using soft tooling to create the rim's tyre channel as well as the hooked bead. This soft tooling allowed for the tooling to be removed from the rim and not be captured by the hooks.”

“However, the soft nature of the tooling inhibited achieving accurate and precise bead seat diameter dimensions.”

Switching to hookless rims enabled the use of rigid tooling and “opened the door for optimised bead seat diameters and therefore a more perfect tubeless system”.

Likewise, Hunt’s Patrick Brown told BikeRadar the cost saving from producing hookless rims instead of hooked ones is “small to negligible”, and it therefore “doesn't factor into our decision making” when designing wheels.

Brown acknowledges that hooked rims are “slightly more complicated to make”, but he says Hunt now uses “three-piece detachable steel mandrels” instead of disposable silicone ones, so producing precisely sized and shaped hooked rims is no longer an issue.

These are more expensive than the solid steel mandrels that can be used for hookless rims, but Brown says it’s “a very small difference” once the cost has been amortised over the life of the tool.

All that said, when Zipp launched its first hookless wheelsets back in 2020, they were substantially cheaper than the hooked wheelsets they replaced. Zipp’s first hookless 303 Firecrest wheelset was around 30 per cent cheaper than its hooked predecessor, for example.

Whether this was due to the switch to hookless rims, or a combination of other factors, is unclear, but this appears to be the point that cemented the idea that hookless rims are cheaper to produce in riders’ minds.

When we look at wheelsets that you or I could buy, there’s no clear trend towards hookless rims being cheaper, however.

In fact, looking at a number of carbon wheelsets from major manufacturers suggests wheelsets with hooked rims may be cheaper on average.

Hunt’s cheaper Carbon Disc and Aerodynamicist wheels use hooked rims, for example, whereas hookless rims have typically been reserved for its pricier options (such as the SUB50 Limitless), which are targeted at more engaged riders seeking marginal gains.

In contrast, Zipp and Giant use hookless rims throughout their ranges, whereas Roval and DT Swiss rims all feature hooks.

While the average prices may bust the myth that hookless rims are cheaper (at least from a rider’s perspective), it’s worth remembering there’s far more that goes into a wheelset than its rim type.

The big differences in price are more dependent on variables such as brand, materials and nominal model tier (flagship, mid-range, budget-focused and so on).

Hunt’s priciest wheelset, for example, is much cheaper than Zipp’s priciest wheelset, which is much cheaper than ENVE’s priciest wheelset. However, I don’t think that has much to do with the fact that the Hunt and Zipp rims are hookless and the ENVEs aren’t.

Are hookless rims stronger than hooked ones?

Improved strength and durability, as a result of the better carbon fibre compaction enabled by solid steel mandrels, is also often cited by proponents of hookless rims.

Cadex, for example, says the groove underneath the bead hook on a carbon rim is 'a weak spot' and therefore needs to be reinforced with extra material, which adds weight. Eliminating this helps to make hookless rims stronger and lighter.

This sentiment is echoed by Jürgensen, who says: “hooks are always a drawback for durability and hookless allows for better impact resistance without adding weight.”

However, Hunt’s Patrick Brown says the aforementioned three-piece steel mandrels provide the same compaction effects as solid steel ones, and therefore “there should be no difference” in rim strength between a hooked and hooked rim now.

Of course, that would only be the case where wheel manufacturers were using these multi-section steel mandrels to produce their hooked rims, but Brown told BikeRadar he believes these are now standard throughout the bike industry.

Do the pros outweigh the cons?

While different brands and people inevitably have different views on the subject, the performance benefits of hookless rims appear marginal at best – if they exist at all.

That chimes with my own experience of riding both hooked and hookless rims, where I’ve generally found there’s no discernible difference in performance.

Variables such as rim depth, width and shape are far more tangible.

And while some hookless wheelsets are cheaper than hooked ones, this certainly isn’t the case in every instance.

All of which begs the question, what is the point of hookless rims?

If the benefits were marginal but there were no obvious downsides, that would be fine. There are plenty of things in bike tech – such as ceramic bearings, oversized pulley wheels, weight-weenie parts, and so on – that provide relatively tiny performance gains, after all.

But that’s simply not the case with hookless rims.

At best, the downsides of hookless compared to hooked rims are reduced tyre choice and lower pressure limitations – but at worst, riders can potentially be risking their safety.

It’s fair to say the case for hookless rims for gravel riding and mountain biking is clearer. The lower pressures generally used in these disciplines make tyre retention less of a concern and the potentially improved rim strength is of more obvious value.

But, for road cycling, it doesn’t feel like a reasonable trade-off for riders.

I said as much in my Giant TCR Advanced Pro Disc long-term review back in 2021, and nothing I’ve seen, read or been told in the intervening years has convinced me otherwise.

The future

In the next and final entry in this series, we’re going to examine what the future might hold for hookless rims.

For a while, it had seemed as if the dominance of hookless rims was inevitable, and that they'd soon become the default for carbon wheels across practically all disciplines.

However, brands appear to be making a marked step change in the opposite direction, at least for road cycling.

At this year’s Tour de France, for example, only three out of 23 teams were using hookless rims – and one of those teams was Tadej Pogačar’s UAE Team Emirates XRG, which spent most of the race using ENVE’s new hooked wheels (the SES 4.5 Pro), rather than its hookless options.

So, are the days numbered for hookless rims, or is this technology here to stay? Might the UCI have anything to say on the subject? Tune in next time to find out.