#thinkwider Aero Design Project

#thinkwider rim design

In 2020, we launched the Strade, our first wheelset using our #thinkwider rim profiles developed in conjunction with the Sports Engineering Department at Nottingham Trent University. #thinkwider introduced a differential front & rear rim profile, designed to optimise performance for the real-world yaw angles observed at the front and rear wheel of the bike.

The front wheel sees, on average, a higher yaw angle so our front rim profile uses a more "blunt", U-shaped design. Prior testing has shown the more rounded shape allows airflow to remain attached for longer around the rim, reducing turbulence and therefore drag. With the rear wheel, average yaw angles are lower, requiring a different design philosophy. Here, a "sharper" V-shaped design has been shown to provide the optimum aerodynamic performance.

You can read all about the original #thinkwider development programme here: https://www.intl.parcours.cc/pages/thinkwider

Following the launch of the mid-depth Strade, in 2021 we applied #thinkwider technology to a shallower rim depth, leading to the launch of our Ronde all-road wheelset. Both the Ronde and Strade set new benchmarks for aerodynamic performance paired with a wider tyre, as well as enhanced handling stability in crosswind conditions.

#thinkwider aero design background

Now we have taken the next step. We wanted to use our experience from the Strade and Ronde design projects and apply our #thinkwider design principles to a deeper-section (>60-70mm+) wheelset. These wheelsets are most commonly seen within three use cases, each with slightly different priorities:

  • Time trial: primary focus on aerodynamic performance
  • Triathlon (predominantly long-course): aerodynamic performance is key, however given the more varied nature of courses and longer ride times, handling stability is also a significant factor
  • Flatter / fast road racing (e.g. crits): aerodynamic performance and handling stability will be considered, as well as minimising rotating weight to allow rapid acceleration

We know from previous development projects (Strade & Ronde) that #thinkwider technology delivers two main benefits:

  • Enhanced aerodynamic performance: by optimising the front & rear rim profiles for the relevant airflow conditions, #thinkwider rims will deliver a greater aerodynamic benefit than equivalent depth standard rims
  • Improved handling stability: focusing on the front wheel, the wider rim width and slightly shallower rim depth reduces crosswind sideforce, thereby improving handling stability in strong crosswinds

Fig 1: Aerodynamic benefit vs. handling stability for Parcours wheels

The chart shows the impact of applying #thinkwider technology to a low profile rim (Grimpeur – 40mm) and a mid-depth rim (Passista – 56mm). In both cases we were able to improve both aerodynamic performance and handling stability. However, we wanted to understand how far we could take this. Would it be possible to focus entirely (or close to entirely) on a single benefit and what would the impact be? The most obvious candidate for this type of testing would be our deep section Chrono wheelset with a 77mm front rim depth and 86mm rear.

#thinkwider aero project goals

Continuing on from the Strade and Ronde projects, any wheelset would therefore need to be:

  • Aerodynamically optimised for a 28mm tyre
  • Tubeless-ready
  • Disc brake-specific

However, when looking at the application of #thinkwider to a deeper section wheel, we decided to split the two potential benefits and look to maximise each one individually. The rationale for doing so was threefold. Firstly, a deeper section rim will present more surface area to a crosswind, thereby increasing sideforce felt by the rider. For a deep section rim, this has a much more significant impact on overall handling than the rim profile or shape, so potential benefits from #thinkwider design are slightly reduced. Furthermore, the introduction of the Strade had created a significant gap in our product line-up for a very fast, yet stable wheelset. Secondly, as our fastest legacy wheelset, the Chrono had already been heavily optimised for aerodynamic performance, meaning again any savings were likely to be smaller than previously seen. Finally, with a deeper section wheelset, the use cases and user requirements for a wheelset are more diverse (see above), so it was important that we could offer the widest possible choice to our riders.

Fig 2: Estimated potential benefits of #thinkwider rim design for deep-section wheel (CFD analysis)

Our initial CFD analysis suggested that applying #thinkwider design to a deeper-section wheelset could offer significant benefits over our existing Chrono wheelset (77/86mm), so the design project would focus on two wheelset options:

Wheelset A: maintaining aerodynamic performance of existing Chrono wheelset, whilst maximising handling stability

Wheelset B: maintaining handling stability of existing Chrono wheelset, whilst maximising aerodynamic performance

Alongside these two wheelset design projects, we added a third element:

Rear wheel C: redesigned rear Disc wheel, to be optimised for running with a 28mm tyre

Prototype test results

The first key finding during CFD analysis was that the front wheel for Wheelset B could be substantially deeper than the existing 77mm Chrono front wheel. Per our #thinkwider design principles, when then applying the c.110% front:rear rim depth ratio, this would result in a >90mm rear rim depth. At this depth, the weight would be close to a Disc wheel, meaning the reduction in rotational drag from a solid rear wheel would deliver superior aerodynamic performance for comparatively little penalty. Ultimately the design group could not conceive of a situation where running such a deep rear wheel would be the optimal setup, beyond very unique circumstances e.g. Ironman World Championship race in Kona, Hawaii where rear disc wheels are banned. As a result, we took four prototype wheels to the A2 Wind Tunnel in North Carolina for final testing and validation, as well as benchmarking against our existing product line-up:

  • Parcours Chrono prototype front wheel A (68.6mm depth / 32.0mm width)
  • Parcours Chrono prototype rear wheel A (75.7mm depth / 30.5mm width)
  • Parcours Chrono Max prototype front wheel B (83.6mm depth / 32.0mm width)
  • Parcours Disc2 prototype rear wheel C

Aerodynamic performance

Fig 3: Front wheel aerodynamic drag at 2.5° intervals

For the front wheels, both new wheels outperformed the existing model at the most commonly occurring real world yaw angles.

Fig 4: Rear wheel aerodynamic drag at 2.5° intervals

Again, both rear wheels outperformed the existing model at the most frequent real world yaw angles. Whilst the shallower Chrono prototype (75mm) was less effective than the current model (86mm) above 7.5° of yaw, the differences remain small and also represent less than 15% of real world ride time.

Fig 5: Total wheelset aerodynamic drag

When looking at a weighted average total drag comparison, both the Chrono (wheelset A) and Chrono Max (front wheel B / rear wheel C) combinations outperformed the existing wheelset.

If comparing with the same 28mm tyre width, the existing model would be almost 5W slower as it is penalised for the narrower rim width.

Another interesting observation was when fitted with a 30mm tyre, the prototype Chrono wheelset was only 0.4W slower than with a 28mm tyre. Whilst the prototype Disc2 rear wheel showed absolutely no difference at all. You can see more on this particular element of the testing in the full white paper.

Handling performance

Fig 6: Front wheel sideforce

When looking at a weighted average total drag comparison, both the Chrono (wheelset A) and Chrono Max (front wheel B / rear wheel C) combinations outperformed the existing wheelset.

If comparing with the same 28mm tyre width, the existing model would be almost 5W slower as it is penalised for the narrower rim width.

Another interesting observation was when fitted with a 30mm tyre, the prototype Chrono wheelset was only 0.4W slower than with a 28mm tyre. Whilst the prototype Disc2 rear wheel showed absolutely no difference at all. You can see more on this particular element of the testing in the full white paper.

Conclusion

The introduction of our new #thinkwider time trial and triathlon wheelset line-up offers riders the option of running a modern, wider tyre without compromising on aerodynamic performance. All new wheels are truly optimised for a 28mm tyre and all outperform our previous generation class-leading wheelset.

Chrono (68.8/75.7mm)
Maintains aero performance of the previous generation wheelset, but is >17% more stable in crosswinds

Chrono Max (83.6mm)
Maintains handling stability of the previous generation wheel, but is 4.1W faster at 30mph

Disc2
First full disc wheel optimised for a wider tyre - no aero penalty up to a 30mm tyre

Riders can choose between the Chrono wheelset which will significantly enhance ride handling and stability and the Chrono Max / Disc2 combination which will further reduce aerodynamic drag.

#thinkwider technology is available in the following models:

Ronde (35/39mm)
Ronde (35/39mm)
Ronde (35/39mm)
Ronde (35/39mm)

Ronde (35/39mm)

$1,449.00
Strade (49/54mm)
Strade (49/54mm)
Strade (49/54mm)
Strade (49/54mm)
Strade (49/54mm)

Strade (49/54mm)

$1,449.00
Chrono (68/75mm)
Chrono (68/75mm)
Chrono (68/75mm)
Chrono (68/75mm)

Chrono (68/75mm)

$1,599.00
Chrono Max (83mm)
Chrono Max (83mm)

Chrono Max (83mm)

$800.00
Disc
Disc
Disc
Disc

Disc

$1,399.00