Josh Poertner, the former chairman of the Bicycle Wheel Technical Committee, has issued a strong rebuttal of the case for hookless road rims, one of cycling’s most controversial topics in recent years, and one that continues to fuel significant debate across the industry.
“Hookless rims are a scam,” says Poertner, now CEO of Silca, a former technical director at Zipp and consultant to a number of professional cycling teams, in a recent episode of the Marginal Gains Cycling Podcast.
In answering a question from a listener, Poertner, who served as chairman of the Bicycle Wheel Technical Committee from August 2012 to September 2013, goes into detail explaining why he believes hookless rims are inappropriate for road bikes, how they have “zero performance advantages”, and why they present “a safety risk” with not enough margin for error.
While he acknowledges certain wheel manufacturers would strongly disagree with his assessments, he also claims that “the only purpose of hookless is to drive down manufacturing cost”.
What are hookless rims and why are they controversial?
Hookless rims – meaning bicycle rims without the traditional bead hooks that help retain a clincher tyre on a rim under pressure – first started appearing on road wheelsets in the late 2010s, but rose to prominence in 2020 when major brands began jumping on the trend.
Brands that have adopted hookless rims generally cite reduced manufacturing complexity and improved performance as reasons behind the switch, but not everyone is convinced. DT Swiss, for example, has stuck with hooked rims “to give the user the safest and widest choice of tyres”.
For more information, check out our hookless rims explainer, which covers everything you need to know about tyre compatibility, the relevant international standards, and how brands design and test hookless rims.
The hookless dilemma
The conversation about hookless rims starts with Poertner’s co-host, Michael ‘Hotty’ Hotten, putting a question to Poertner from listener Mike Thompson, about “the hookless dilemma” and, specifically, what Poertner thinks would be the best tyre setup for a new set of wheels they’ve ordered.
As the Hunt SUB50 Limitless wheelset in question has hookless rims, Thompson – who self-identifies as a “marginal gains seeker” – wants to know whether they can continue using their preferred tyre setup, comprising a 28c rear tyre and a 25c front.
Thompson cites wanting to stick to Poertner’s ‘rule of 105’ (which says “the rim must be at least 105 per cent of the width of the tyre to recapture airflow as efficiently as possible”), and says he has been using Silca’s online calculator to determine his optimal tyre pressures.
According to Thompson, Silca’s calculator recommends pressures of 76psi / 5.2 BAR up front with 70psi / 4.8 BAR at the rear.
As the recommended front pressure is above the ETRTO’s (European Tyre and Rim Technical Organisation’s) 72.5psi / 5 BAR maximum permitted pressure for hookless rims, Thompson asks whether the potential aerodynamic benefit of such rims would offset any performance losses from needing to run a potentially lower-than-ideal tyre pressure up front.
In response, Poertner says Thompson’s “not going to like this answer… [but] there’s no aero benefit to hookless rims”.
The idea that hookless rims may be more aerodynamic than ones with tyre bead hooks, Poertner says, has been “postulated and theorised by brands making hookless rims” but is “just not true”.
“In the real world, we’ve never once seen it to be true in an actual wind tunnel doing actual testing,” Poertner adds.
Far from there being any potential benefits, Poertner says there’s more likely to be a detrimental effect to aero performance because hookless rims tend to make tyres inflate “a little bit wider than they otherwise would, making it not possible to meet the rule of 105 in almost all instances”.
It’s not just about performance
Aside from questions about performance, Poertner also points out that Thompson’s proposed setup falls outside of ETRTO recommendations in another way.
With a 23mm internal rim width, the Hunt SUB50 Limitless wheels have a minimum tyre width of 28mm, according to the ETRTO and, indeed, Hunt itself.
Using a 25c tyre on those wheels would therefore be “a really dangerous thing to do,“ says Poertner.
Notably, this is something Hunt agrees with. Per its website, Hunt says the SUB50 Limitless rims are “ETRTO compliant for use with 28c tyres and wider”. It also confirmed 25c tyres are not compatible with these rims.
According to Poertner, ignoring this limitation can increase the likelihood of suffering a tyre blow-off “dramatically”, and he claims to have seen “tyres like that blow off on hookless rims as low as 78 to 80psi”.
Although moving up to a 28mm-wide front tyre would solve Thompson’s pressure and safety issues, Poertner says it might still come at the cost of some performance.
“Those 28s are going to measure 30 [millimetres-wide], and so you can't meet the rule of 105.”
Hunt disputes this specific claim, though, because while the SUB50 Limitless rear wheel has an external width of 30mm, the front wheel has a 34.2mm external rim width – 14 per cent wider than 30mm. The wheelset is also claimed to be optimised for 28 and 30mm-wide tyres.
According to Hunt, simply focusing on a tyre and rim’s combined frontal area ignores other critical factors such as aerodynamic performance at higher yaw angles, and factors such as grip, comfort and rolling resistance.
It didn't put a figure on it, but Hunt also said it believed there is a "marginal aerodynamic benefit" to hookless rims, but mainly at higher yaw angles where the tyre and rim interaction becomes more critical.
Likewise, while Hunt agrees narrower tyres may be more aerodynamic in a wind tunnel, it said it designs its rims taking into account the tyre sizes riders actually intend to use. It notes 28c is “by far” the most popular tyre size it sells (Hunt offers the option to purchase wheels with compatible tyres), with 30c already overtaking 25s in terms of sales volume.
In general, though, Poertner says the problem with hookless rims for road use is “your tyre always ends up being bigger than it should be, but it can't get any smaller for safety reasons… and so you’re giving up aero properties”.
Despite this, Poertner says the Hunt wheelset is “a good, solid, aerodynamically competent wheelset with the 28mm tyres“, even if there are potentially faster setups.
Strong opinions
Delving further into the subject, Hotty asks whether hookless rims can ever achieve the optimal balance of aerodynamics and tyre pressures, to which Poertner responds: “not for road.”
He concedes hookless rims are “totally fine” for mountain and gravel bikes, where tyres are much wider and pressures far lower, but says that hookless rims for road bikes will always be constrained by the need to run wider tyres or lower pressures than is optimal.
Poetner says, “It's a strong word… I think it’s a scam. I think it’s way less safe than it needs to be, and it has absolutely zero performance advantage in any area of performance – and actually it likely has some performance detriment somewhere or another”.
Furthermore, Poertner says he believes “manufacturers came up with hookless because it saves them money when they make the rims”, while also bemoaning the idea that some brands are selling wheelsets with hookless rims that are “every bit as expensive as the hooked rims they replaced”.
That hookless rims can be cheaper to produce is something Zipp has previously acknowledged. The brand says this isn’t the only factor driving its decision to produce hookless rims, however, citing other benefits such as lower weight, higher impact resistance and tighter tolerances.
Zipp also passed some of these savings onto riders in the form of lower prices, at least initially. When it launched its first hookless 303 Firecrest wheelset in 2020, for example, it cost £700 / €800 / $600 less than the previous hooked iteration.
Poertner says he envisages he’ll have “six manufacturers in my e-mail box tomorrow really pissed off” about his comments, “but I continue to not be a fan.”
Not enough margin for error
Summing up his arguments, Poertner criticises what he sees as a lack of margin for error with hookless rims, saying they’re unlike “any other historical cycling product” in this regard.
“In our lab, on highly calibrated equipment, we've seen tyres that are approved to work with [hookless] rims blow off as low as 78psi… It’s just such a safety risk for no other benefit.”
This is a sentiment previously echoed by Dan Bigham, head of engineering at Red Bull – BORA – hansgrohe, and a prominent voice in the current debate about safety in the pro peloton.
In the wake of Thomas De Gendt’s infamous tyre blow-off and subsequent crash at the 2024 UAE Tour – which occurred while he was using 28c Vittoria Corsa Pro TLR tyres on Zipp 353 NSW hookless rims – Bigham posted on Twitter / X saying: “History will not be kind to road hookless” and “I don’t consider factors of safety as low as 1.1 as “fine.”
Following that incident, the UCI (Union Cycliste Internationale – cycling’s international governing body) launched an investigation into hookless rims and related incidents.
Less than a month later, in late March 2024, the UCI issued a directive reminding teams of the requirement to comply with the latest ISO (International Organisation for Standardisation) standards, and said it would “carry out an in-depth analysis” of its regulations surrounding this topic, to help “guarantee the safety of riders”.
Although Vittoria, De Gendt’s tyre sponsor, claimed the incident was “unrelated” to the fact De Gendt was using hookless rims, it began producing 29c tyres later than year to help its sponsored-professional teams comply with ISO and ETRTO recommendations for 25mm-wide rims (which have a minimum tyre size of 29mm).
We first spotted these 29c tyres on Jonas Vingegaard’s Cervélo R5 at the 2024 Tour de France, with an official launch of these 'Wide Rim Optimised' tyres coming earlier this year.
These tyres, Vittoria says, offer “a perfect and cohesive profile which minimises micro-turbulence” and improves aerodynamic performance.
In other words, they attempt to address the problem Poertner notes about tyres always being wider than is optimal (for aerodynamic purposes) on hookless rims.
It’s not clear whether Poertner is aware of these 29c Vittoria tyres, or similar examples such as Continental’s recently launched Archetype – a 30c tyre said to be optimised for the 32mm-wide ENVE SES 4.5 hookless rims UAE Team Emirates XRG has in its equipment arsenal.
However, it’s also notable that defending champion and hot favourite for this year’s race, Tadej Pogačar, has been using ENVE’s new SES 4.5 Pro wheelset at this year’s Tour de France, which uses rims with a narrower internal width and ‘mini-hooks’.
Whether this is an isolated example or a signal of a wider trend back towards hooked rims remains to be seen, but it seems road cycling’s “hookless dilemma” is far from settled.
