Whether or not you count yourself amongst the tech geeks of the cycling world, odds are that at some point over the past 6-12 months you’ll have heard someone expressing their opinion on hookless rims. Are they faster? Are they cheaper to make? Are they even safe to ride?
We don’t want to go over old ground here, so you can find the answer to the first part of the question here: https://www.parcours.cc/blogs/news/hooked-vs-hookless
Or at least our perspective on it here at Parcours.
But arguably the bigger question recently has been in relation to safety. After a few notable incidents, there was a sudden focus on standards defined for tyre & rim compatibility that (in theory at least) should prevent such potentially dangerous mishaps from occurring. You’ll have heard of acronym-heavy organisations like ETRTO or ISO. But who are they, how do they set their guidelines and are the guidelines actually still fit for purpose?
The key body involved in setting standards for all things tyre and rim-related is the ETRTO, or European Tyre and Rim Technical Organisation. Whilst (by name and governance), ETRTO is a European organisation, it has become the de-facto global standards body for tyres and rims since ISO (International Standards Organisation) took the ETRTO standards and incorporated them in their own publication of ISO 5775. From there, individual countries’ standards bodies will more often than not just take the International standard from ISO & apply it locally. In the UK, where Parcours is based, this comes through from the BSI (British Standards Institute) in BSI ISO 5775.
So far, so (almost) clear. However, it’s still interesting to note that whilst all these bodies can set a standard, there’s no explicit requirement for any manufacturer to abide by these guidelines and standards. The enforcement (if required) sits elsewhere. And again this is country-specific. In the UK, for example, it would be Trading Standards who would be responsible for enforcing any action against a dangerous product. Even then, however, any enforcement would be made under the General Product Safety Regulations (2005). This states that when a product conforms to a voluntary national standard of the United Kingdom, it will be presumed to be safe.
The shorter version distils down to: ETRTO writes the standards then leaves it to others for any enforcement. And that will vary by country, albeit seemsbroadly similar in most larger economies.
At this point it’s worth understanding who actually is part of ETRTO and sets these standards. Given it’s a European organisation, it won’t be a surprise to learn that it’s made up of European manufacturers, split between rims and tyres (and valves). Some global (non-EU) businesses are represented by a European subsidiary. There is also a corresponding member list who will provide input to discussions. Looking down the membership list (https://www.etrto.org/Members/Current-Members) shows that the tyre members far outweigh the rim members in terms of size – remember that the cycling segment of the likes of Continental, Goodyear, Michelin & Pirelli will be dwarfed by the various automotive segments.
But what remains interesting is that you effectively have two groups (rim manufacturers & tyre manufacturers) that sit as part of the same organisation that will ultimately define the standards for the interaction of those two pieces. Although that the tyre manufacturers are significantly larger so would potentially carry more weight in discussions.
Now that we have a clearer idea of the various standards bodies and who is involved in setting those standards, it’s worth taking a look at the standards themselves.
What does ETRTO say?
A lot. The latest ETRTO standards manual stretches to several hundred (helpfully unnumbered!) pages. Of which the cycling-specific sections now comprise a reasonable chunk.
The standards document defines, amongst other things:
- Tyre sizing, how they’re measured, what size is suitable for what size rims
- Inflation pressures, maximums not minimums
- Rim sizing, including strictly defining each parameter
But from the published standards, you can determine what size of tyre is compatible with what size & type of rim, then the pressure at which you will be able to safely run that setup.
It does not explicitly state that if any part of a rim/tyre system is outside of the defined standards that it is dangerous. But it does state that if the system is within the defined standards that it is safe to ride.
What do I need to know about it?
Despite the fact that ETRTO standards are becoming more widely-quoted, there are still some details that aren’t so widely-understood or discussed.
- A tyre will only measure the size printed on the packaging when fitted to the defined size of reference rim. But the size of reference rim varies by size of tyre
What this means: the actual casing width of a tyre might not vary from size to size. For example, a 28mm tyre (stated) should measure 28mm on a 19mm internal rim width. A 30mm tyre (stated) should measure 30mm on a 21mm internal rim width. The casing width on these two tyres should therefore be more similar than you think! - All compatibility standards are based on stated tyre size, not measured. So the actual size of your tyre when fitted has no bearing on compatibility
What this means: you have to read the packaging and also assume that it has been sized correctly - There is no differentiation in the tyre/rim size compatibility table between a hooked and hookless rim
What this means: according to ETRTO, adding a hook does not allow you any more freedom in choosing a tyre size - 72.5psi is not a blanket maximum pressure for all hookless tyres
What this means: if you are running e.g. a 30mm tyre on a hookless rim, the maximum pressure is 65psi. For a 35mm tyre this drops to 58psi, and so on as the tyre size increases
Are the current standards fit for purpose?
If any part of this post so far has seemed confusing or contradictory, possibly not. Equally, if you weren’t aware of, or were surprised by any of the points above, again possibly not. However, it is worth bearing in mind that as recently as 2015 the extent of the standards relating to cycling ran to around 3 pages out of the several hundred published by ETRTO. So things are moving in the right direction.
But arguably there is still some way to go, for two main reasons:
- The tyre companies appear to hold too much influence in setting standards
This reflects the fact that many of the leading bike rim manufacturers are either too comparatively small, or not based in Europe, to sit on the ETRTO membership. But it does mean that many of the pressure limits or size limits applied to more progressive rim designs are potentially being held back by conservative tyre manufacturers. And also can come across as somewhat arbitrary. - The standards are too complicated
We are in a situation where experienced cycling industry professionals are left debating what the standards mean and what is/isn’t compliant. So what hope does a weekend enthusiast have of understanding what they should do with their rim & tyre setup?
What should be done about it?
It’s not an easy solution. These standards exist to offer a safety net for the consumer and give them confidence in setting up their bike. So on the one hand they should be inherently conservative. However, there is a lack of transparency in explaining how these conservative standards have been defined and set.
Cycling occupies a unique space in the ETRTO sphere of influence. Pressures are higher (especially on road bikes), tyres are far smaller and it remains the only system where you conceivably need to be able to remove the tyre from the rim without mechanical assistance. But at the same time it represents a far smaller market than other types of tyre/rim combination.
However, a good first step would be to add some level of transparency around what testing has been conducted to set standards, especially those that could be argued to be potentially holding back progress and freedom of development in design.
Secondly, there has to be a concerted effort to educate and inform riders about the standards that define what is safe to ride. Whether it should be down to wheel manufacturers, tyre manufacturers or someone else will no doubt be debated, but ultimately it has to be in everyone’s interest to ensure that riders can clearly understand what is (and isn’t!) safe.
Despite all this, the standards exist for the primary reason of rider safety. And it's for this reason, regardless of the potential flaws in the current standards, that Parcours as a manufacturer has to abide by and follow the standards as published.
Whilst Parcours may not yet be of the size to have a voice at the ETRTO table and move things forward, wemust at least do what we can to educate and inform our riders about how to think about their wheel & tyre setup. So if you have any questions, queries or thoughts about this or any other setup consideration, please don’t hesitate to get in touch!
