A Rare Insight into Wheelset Design: Swiss Side Hadron
- by Christopher Jones
- Published: 22 April 2014
How often do cycling companies open their doors to reveal all? There is the risk of revealing too much, losing the competitive edge, or releasing unqualified information and creating a PR nightmare. The doors usually remain closed and the marketers keep a watchful eye on all external communication. This means that cyclists (consumers) are faced with a minefield of marketing jargon and technical acronyms.
What if cyclists were given the opportunity to peak under the hood? What if a cycling equipment company was prepared reveal everything… just to satisfy the interest and curiosity of the cycling community?
On Bicycles Network Australia discussion forums we recently provided the rare opportunity to “ask away”. The young wheelset company Swiss Side graciously got involved in the Australian Cycling Forums discussion to coincide with the development of their new hybrid alu-carbon wheelset called the Hadron.
As a young wheelset company (founded in 2011), Swiss Side have chosen a “direct to customer” business model which allows them to compete by promoting wheelsets with the same quality and performance as the big name brands, but at a fraction of the price. The internet is core to their communication strategy as well as consciously exploring different approaches to find their audience. Swiss Side were open to the suggestion of ‘laying their cards on the table’ and taking questions, as well as criticism, directly from the community.
This article compiles the discussion into a structured format and provides insights into the development process and key decisions in building their new wheelset.
Part 1 – The foundations of the Hadron wheelset
Credentials: With the new Hadron wheelset, Swiss Side have set out to create the “most aerodynamically advanced performance wheelset”. Considering Swiss Side are such a young brand, this seems like a contradiction, so what makes you qualified?
“We take our knowledge & development methods from F1 (which is normally held tightly in the F1 circles), and used it for developing the Hadron wheel. We mean it when we say that this team below was undoubtedly the most experienced aerodynamics crew to ever set foot in a wind tunnel for a bicycle industry related test.
In the image below, you can see our wind tunnel testing crew. From left to right, you have James Eddison (15 years in F1), Jean-Paul Ballard (co-founder Swiss Side, 13 years in F1), Christian Kleiner (8 years in F1, previously BMW motorsport superbike aerodynamicist), Seamus Mullarkey (22 years in F1 and former Head of Aerodynamics & Chief Aerodynamicist). All of these guys are still currently involved in F1 and are all also very experienced cyclists.
Swiss Side make no illusion as to why they are drumming the “Formular 1” message into all of their communication…
“Marketing… of course! We have to get our message out there. Repeating the word F1 everywhere… Absolutely, because it’s real, as is the performance of our products for this very reason! We challenge any other brand to match our transparency of development reporting, the experience within our team, the performance of our products, and our incredibly low and FAIR pricing.
How real is the community input? During the development of the Hadron, the global community was invited to provide input on all key factors, for example whether it should be a full carbon, aluminium or a hybrid. But was this feedback taken onboard?
“Within the parameters we set we were very open to feedback from the community. We launched the project with the goal of engineering and developing an industry leading aerodynamic wheel set at a significantly lower price than the big brands. Within this scope we wanted to hear from the public so that they could help to steer our decision making process and we could develop a wheel that would tick the right boxes for the majority.
As far as the community input significantly changing the direction of the project, we’ve found that for the most part the feedback has aligned with our initial spec proposal and has more so reinforced the development direction we initially had in mind. With that being said, we’ve found ourselves referring back to the feedback on many occasions throughout the process and making decisions with this feedback in mind. If we had found that the community feedback indicated that the project should be moving in a different direction then yes, we definitely would have questioned our direction and the final output would most likely be different.
Early prototypes of the hybrid Caron Fibre AlumInium Hadron wheelset (left without the cladding).
Considering that cycling is very fashion oriented, how has this influenced the development of a new wheel. For example, the ‘needs’ of the community can shift by the time the wheelset is ready to ship.
“Our approach at Swiss Side for the Hadron wheel set was simple, to produce the best aerodynamic wheel set on the market. Therefore we were determined to let science drive the direction. However that said, it is important from a brand perspective that we produce something which people want to buy. So there is always a little bit of compromise. For example, in order to produce the absolute lightest weight and stiffest wheelset, we would have gone down the direction of a carbon tubular rim, however such a construction is not one which many people like to use. So in this case we clearly wanted to go down the clincher route, and our preference was the carbon-alu hybrid construction as this offers the best all round usability. Luckily from our original survey, the public input matched our direction so that was a win-win so to speak.
With this wheelset, which type of cyclist is this targeted towards?
We are targeting as broad a market as possible. Clearly this is a more ‘aero’ driven wheel however we were confident that we could match the aerodynamic performance of 80mm deep profiles but with a 60mm deep profile. And we have! This was also our intention because we feel that 60mm profile rims are also a lot more appealing than larger ones for everyday use.
Cyclists are individuals, and notably with regard to weight. Does this mean that the Hadron is less suited to certain cyclists?
“We are trying to cover the broadest weight range as possible with the Hadron without going overboard. Therefore the Hadron is spec’ed for riders up to 105kg. If we were to design specifically for light weight riders we could remove some more material from the rim and reduce the spoke count (say to 16-21). The weight saving for this would be in the order of 50g for the wheel set. The aero saving would however be extremely small. Therefore as the Hadron is specifically targeted at the aero wheel market, eg. triathlon where races are predominantly flat, we were happy to accept the slight additional weight to make the wheel accessible to a larger market.
One of the biggest developments in road racing is disc brakes, have you considered this for the Hadron?
“Our goal for the Hadron was clear… To produce the world’s most aerodynamic efficient wheel set. At the same time we were well aware of the introduction of disc brakes to the road bike market. So as part of the Hadron aerodynamic development investigations, both in CFD as well as in the windtunnel, we evaluated brake disc wheel designs, even if we were sure they would be inherently draggy. The aerodynamic drag penalty of the larger hub required for the disc brake, together with a 130mm brake disc was confirmed to be in the order of 10%-15% across the yaw range which is quite significant. Therefore for this Hadron wheel, a disc brake configuration was ruled out. However we are currently working on a Gotthard Disc wheel model right now and we will definitely look at producing a Hadron Disc in the future.
Another part of the equation in a competitive marketplace are competitors, where does the Hadron fit?
“We are targeting all of the absolute top level wheels including those you have mentioned. Our target is to beat them aerodynamically and match them as close as possible with weight, but at a hugely reduced price (around 40% less). As cyclists ourselves, we were sick of the overpricing of products and started Swiss Side because we knew we could do a better job for a lot less! We also want them as usable as possible -hence choice of carbon-alu hybrid with alu braking surface so people can swap their wheel sets around without the hassle of changing to carbon brake pads. We also limited the braking track width to 23mm so that the wheels fit all bikes without issues.
Part 2 – The Swiss Side Approach
With a task of designing this wheelset, how have you prioritised the design requirements?
1. Aerodynamic efficiency,
2. Broad usability (hence choice of carbon-alu hybrid with alu braking surface),
In this high-tech world how does Computer Modelling and Computational Fluid Dynamics (CFD) compare with old fashioned physical and real world testing?
“We’d like to say there are equal measures of computer / mathematical simulation as well as skill. Like any tool or instrument, the quality of results is only as good as your know-how and skill in how to best use it.
“With the types of advanced methods we are using in our CFD approach, for a bike wheel development we can confidently get extremely close to the final real world solution in the ‘virtual CFD world.’ However a simulation is always just a simulation and real world testing is always necessary in order to confirm the results. Therefore we naturally took the best Hadron concepts to the wind tunnel. You’ll be able to read about this in the coming weeks when we again publish a transparent report on our wind tunnel testing methods and results. We can tell you already however that the correlation to CFD was excellent which was a great confirmation to us of the methods and approach we have developed.
With the advent of velodrome aero testing for athletes do you think you could put your wheels through the same testing procedures to compare to competing brands in near real world settings?
“We completely agree that the only place where the results matter are in the real world. To do this we took the best Hadron concepts to the wind tunnel rather than to the velodrome. The best place for validation of a wheel design is in the windtunnel because it is a fully controlled environment where we can measure the forces very accurately and repeatably, but also importantly, across a large range of cross wind angles which is where a good efficient aerodynamic wheel proves it’s worth.
Computational Fluid Dynamics Testing of the Hadron profile
Using CFD to design the ‘Optimal Rim Profile’, is this a process of trial and error or were you already close to the mark with your original designs?
“With the in depth knowledge and experience in aerodynamics we have in our team, we had a very good idea of the general profile shape which would most likely bring the best results. So we defined our ‘best guess’ starting point and defined the range for optimisation of each parameter. From this point we didn’t simply follow a random trial and error process for the parameter investigation, however applied a mathematical processes for determining what geometries to run in CFD in order to understand the sensitivities of each parameter (profile width, depth, height of the wide point, etc). The approach used for defining the discrete parameters for investigation is called a ‘Latin Hypercube’ sampling method. The geometries for each parameter variation are then calculated in CFD and the results output to create ‘response surfaces’. These are basically multidimensional mathematical surfaces defining how the parameter variations affect the performance measures- in our case, drag and side-force.
“Each ‘response surface’ is refined by running further CFD cases until it becomes stable and no longer changes significantly. At this point each response surface can be ‘interrogated’ to determine what parameter groupings result in the lowest drag and side-force performance, (in this case the minima of the response surfaces). We can literally mathematically evaluate hundreds of parameter combinations via the response surfaces without needing to calculate all of them in CFD. The advantage of this method is that we can achieve a much better understanding of the parameter sensitivities to performance with a lower number of runs. So we hone in on the final best performing geometries quicker and can then continue with a much refined CFD optimisation in a more focused parameter range.
“With this combination of mathematical modelling combined with the absolute latest cutting edge CFD methods from Formula 1, we are able to define the final Hadron test profiles (for testing in the windtunnel), with around 40 actual wheel profile geometry runs in CFD.
Part 3 – The Hadron Wheelset in detail
Rim Profile: The Hadron ‘bulges’ which is thecurrent trend in other top wheelsets – moving away from a triangular profile. How far is this design/engineering direction guided by the competition and how far is it guided by independent research and calculations into the most effective profile?
“We’ve taken a full Formula 1 development approach to engineering the Hadron wheel set, right from the structural design through to the aerodynamics. When it comes to developing the most effective profile, we’ve utilized advanced CFD (computational fluid dynamics) methods to drive the rim shape optimisation. Through this CFD optimisation process we are able to explore the performance of a wide variety of rim shapes within a series of pre-defined shape variations. The end result is that we can see the performance differences between each variation allowing us to select the profile that performs best. CFD development is then followed by prototyping and windtunnel testing.
Rim Profile: Yaw has become one key factors in measuring the aerodynamics of a wheel and in simple terms indicates the amount of drag from crosswinds at different angles. In the wind tunnel testing of the Hadrons, the team was excited that to see how it compared against big name wheels, does the Hadron have less drag across all yaw angles?
“The Zipp 808 was our benchmark wheel in the windtunnel. The Hadron matches it’s drag throughout the yaw range within 1-2% but delays the stall point later, offering lower drag at those higher yaw (crosswind) angles. But the big effect is the 25% reduction in sideforce. This is worth significant performance and was specific performance wish from our pro as well as amateur Swiss Side riders. The higher the yaw angle the bigger the effect.
Rim Profile: What does 25% less sideforce mean in layman’s terms?
“25% less sideforce means you won’t get blown around as much on blustery days which is important when considering overall drag. The rider actually represents about 80% of the total drag. If you are getting blown around and constantly having to get out of your tucked aero position to correct and adjust, the drag consequences are huge! Our pro riders strongly pointed out the importance of reducing the effects of being blown about because it allows them to keep tucked and on the power. So we pushed to optimise for reduced sideforce and steering effects.
“In the end, in terms of real life drag performance, on a day where some wind is present, we are confident the Hadron will outperform any aero wheel on the market!
Rim Width: Why opt for a 23mm brake track and toroidial shape when most manufacturers are going wider at the brake track with less bulge??
“Braking tracks wider than 23mm lead to issues with clearances on some bike frame makes. Therefore we wanted to avoid such issues to keep the appeal of the design to as broad a market as possible. Analysing the flow field mechanisms at work as a part of the initial CFD investigations, we were confident that we could achieve our aerodynamics targets with the 23mm brake track width. Ultimately we proved this. The Hadron outperforms the Zipp 808 Firecrest aerodynamically in all aspects! We confirmed this result as part of our wind tunnel testing.
Braking Surface: The hybrid design with aluminium braking surface has advantages over a full carbon wheelset, but are there other materials or compounds that can be used as a braking surface with the durability and longevity of aluminium but without the additional weight?
“The issue with carbon braking surfaces is that you need heat to get them to work properly. On F1 car carbon discs & pads, to get the high friction coefficients for braking you need to be up around the 600C mark. This is not feasible on a bike wheel because you would need a hell of a lot of energy to develop those sorts of temperatures, and then it would delaminate your carbon wheel and burst your tyre all at the same time. So not a good solution. So basically the use of carbon fibre in bike wheels is only for the weight & stiffness. The braking performance is always going to be compromised. Soft cork pads are used on carbon braking surfaces as these provide the highest level of friction, however for very high wear and poor performance in the wet.
“As for other braking surface or treatments, as other manufacturers have done, we have experimented with ceramic coatings on braking surfaces. These offer a different braking characteristics over aluminium for massively reduced rim wear. In the dry they are great but in the wet they are terrible. In addition, you need to use special brake pads for ceramic rim coating. However the coating application drives the price up massively and ultimately it is not of interest. All in all, aluminium braking surfaces are pretty much as good as it’s going to get. If you are keen for improved braking, then (steel) disc brakes are the way to go, but be aware that you’ll carry the 10-15% drag penalty on the wheels for running these.
Spokes: Will you design your own spokes or go “off the shelf”? What about the material selection for your spokes?
“Over the last few years at Swiss Side we have taken a detailed look into spokes, shapes and materials. From an aerodynamics point of view, a good small section bladed spoke has a minimal impact on the aerodynamics, orders of magnitude less than that of the rim and hub. The best ‘aero spoke’ on the market is the Sapim CX-Ray because it uses a minimal section elliptical profile. Many of the ‘big brands’ are using this spoke even if they do not publicise it.
“As far as materials go, we choose to stick to high grade stainless steel which is what Sapim makes all their spokes from. The durability of the wheel is clearly a major factor and we do not want to compromise on this. The Sapim CX-Ray spoke actually has the highest fatigue rating of any spoke on the market. See our comments from our FEA report. An alternative with which have experimented in the past is aluminium spoke construction, but due to the material properties and in particular the fatigue characteristics of aluminium alloys, the section has to be increased significantly to the point where no weight saving is possible and the aerodynamics are compromised. Titanium spokes could potentially offer weight savings however compared to the CX-Ray, the saving would be tiny and would compromise the durability of the wheel, something we are not prepared to do for a few grams of weight.
Hubs: Can you describe the preference for an aluminium freehub over a steel freehub? What is the weight penalty for steel is and are other considerations beyond weight in favor of an aluminium freehub?
“Our choice to use aluminium cassette bodies is weight and cost driven. We can save up to 30g depending on the design which is quite a lot for a hub assembly. Also as the cassette body requires quite some machining, it is more cost efficient to machine aluminium than steel. In this way our customers end up with a lighter and cheaper solution.
“The only down side with aluminium cassette bodies is the potential for notching where the individual middle gears can push into the softer aluminium under high load. It is important to note that this notching is not uncommon in aluminum cassette bodies and poses absolutely no problem except for the cassette on occasion being a bit sticky to disassemble from the cassette body. The edges of the notches can be filed down if desired without any adverse effect on the function of the cassette body. However by cleaning the cassette elements correctly upon assembly and ensuring the correct fastening torque is applied to the locking nut, this notching can be minimised or avoided altogether. We have yet to see a case where notching has created a problem.
Part 4 – A better wheel and a better price?
The test results and responses show that you closely match the Hadrons up against some pretty big and well established competitor brands. These brands have built their brand legacies over a much longer time frame and Swiss Side is, in comparison, a newcomer. Plus aerodynamics are just one part of the equation. Can Swiss Side really match or improve wheel performance and why wouldn’t the bigger established brands not already be a step ahead considering their market position?
“We see ourselves overall in a stronger market position than the big brands and this is the reason cyclists should choose Swiss Side! Let us explain:
“The fact that we do not have the baggage of a long legacy means that we are free to do what we want so to speak. The entire brand concept, resulting in the incredibly low pricing we offer is one aspect of this. Our brand target is the ‘same or improved quality and performance but for at least 40% less’. We achieve this through our ultra-streamlined online business platform which cuts out all the middleman levels to keep the cumulative cost in the supply chain to a minimum. Note also that our quality remains uncompromised. We use the same factories for our production as ‘the big brands’.
Swiss Side Co-Founder George Cant in Sydney
“From an engineering and design stand point, again as we don’t have a long legacy we are completely free to follow any design paths we choose. As shown in our aerodynamic development, we take an objective engineering approach in all areas. We determine the relevant technologies available, the pros and cons of the various concepts on the market including our in-house ideas, and we design what we ‘calculate’ to be the best. Eg, Our choice of a hybrid carbon-alu construction for the Hadron shows this well. The market is driving full carbon clinchers right now but we calculated that with the hybrid construction, we could achieve a much more user friendly and broad appealing wheel design for the same weight, performance and lower cost to our customers.
“Learning through experience is of course a valuable point. Our team however brings a very impressive calibre of engineering, design & production experience from absolute top-end engineering industries (including Formula 1). Our base level of engineering ability is therefore very high. The Hadron project in its entirety (not just from the aerodynamics side) showcases this know-how. We are also no longer total newbies, and have been designing, producing and selling our own wheel designs since over 3 years now. Our methods and processes from design to the supply chain are already well honed.
While this concludes the ‘rare insight’, in my own experience Swiss Side have been very transparent and receptive in answering questions, even the hard ones. They are a relatively new brand and after three years now boast a solid range of wheelsets from entry level through to competition carbon tubulars. The Swiss Side brand quality has been confirmed in our reviews on BNA of the Francs (review 1 and review 2), reviews by other cycling media as well as my own experience riding some other their wheelsets and chatting to other cyclists with Swiss Sides wheels. And they also offer local customer support for Australian’s. So yes, I am a fan and thank Swiss Side for taking the plunge and taking part in the forum.
The Swiss Side Hadrons are due to ship on June 30 and they are now taking pre-orders for the Hadron Wheelset (which may be shortly sold-out). For Australians the price, including shipping to Australia, is $1094 (GST and Customs Duty will be levied on imports over $1000).
For more techie details, the entire wheelset development process is also documented on the website: www.swissside.com/hadron
Christopher Jones (your author) with the first pre-production set of Hadron’s in Australia