Bicycle.Engineering

Bicycle.Engineering Bicycle.engineering develops bicycle parts and frames that are licensed to factories that produce an

: Just being back from another trip to the wind tunnel, I thought I'ld share a bit about an older visit during the deve...
18/08/2026

: Just being back from another trip to the wind tunnel, I thought I'ld share a bit about an older visit during the development of the Windrad. We played with the thought of using turbulators to keep the flow attatached for longer and delay stall. We tried multiple positions and patterns, but in the end we could not find any gains, in best case we did not add drag. A lot of our job is trial and error, and failing is just part of it.

: Different protocols create different results. With the launch of the new Tarmac, it was communicated that the develop...
14/07/2026

: Different protocols create different results. With the launch of the new Tarmac, it was communicated that the development was focused on a narrower range of yaw angles, something we think is a reasonable assumption. What was not communicated is how that can affect results.
Another point that can influence results is the data points you have. The GST wind tunnel we (and Tour magazine) use measures drag on a continuous yaw sweep. Other wind tunnels measure at discrete yaw angles.
Based on the example of wheels, we show how these two factors can affect results. The DT Swiss wheel benefits from a significant sailing effect at -10° yaw. How this shows in the results depends a lot on the weighting function, and how many data points you have. None of the results are wrong, but they can lead to very different perceptions of what a fast wheel is.

Your aero advantage might not be what the number suggests, part 3:Ambient wind speed plays an important role in how wi...
16/06/2026

Your aero advantage might not be what the number suggests, part 3:

Ambient wind speed plays an important role in how wind-tunnel gains translate into real-world benefits.

The stronger the ambient wind, the wider the yaw-angle distribution a rider experiences. Since the well-known “sailing effect” usually appears at higher yaw angles, more wind often means larger measured aero gains on the road.

Many yaw-weighted averages seem to be based, directly or indirectly, on publicly available wind data. That is a sensible starting point, but it comes with two important caveats:

We rarely choose to ride in stormy conditions, but those days are part of the recorded wind statistics.
Wind speeds are typically measured 10 m above ground. Close to the road surface, the wind speed is significantly lower, as shown in the distribution graph.

The result: yaw-weighted wind-tunnel averages may be biased toward higher yaw angles than what many riders actually experience on the road in normal riding weather.

: Your aero advantage might not be what the number suggests, part 2: Wind speed.Most testing in wind tunnels is carried...
09/06/2026

: Your aero advantage might not be what the number suggests, part 2: Wind speed.
Most testing in wind tunnels is carried out at wind speeds of around 45 km/h. There are good reasons for this: for example, measurements are more repeatable at higher speeds. It also sounds like a reasonable speed, given that the average speed in many races is now at this level. However, the speed at which the peloton is riding can differ greatly from the wind speed experienced by the riders. The convoy of cars and motorbikes that accompanies the race can have a significant impact, and obviously there is drafting whithin the peloton. If we look at data from races and compare the recorded power to what it should be if we calculate it based on riding speed, most of the time there is a big difference. So even in professional racing (mass start, not time trial), we yet have to find an example where the savings over the full distance of a race matches the savings found in a wind tunnel.
Obviously 45 km/h is a speed most of us rarely achieve, but how much of an impact does it have? Quite a lot:
- at 35 km/h, you get about 47 % of those gains measured at 45 km/h
- at 30 km/h, this is down to 30%

: your aero advantage might not be what the number suggests, part 1.We split this into multiple parts, because it is a ...
02/06/2026

: your aero advantage might not be what the number suggests, part 1.

We split this into multiple parts, because it is a big topic: aero claims are often true, but at the same time implying bigger gains than there really are.

But first, let me state this: aero gains are absolutely real, und you are benefitting from them. They just might not be as big as you think. Also, aerodynamic drag will most likely be your main resistance during riding.

In this part: how did we get to this point where most aero testing ends up in numbers that are very hard to achieve in real-world use? I believe it is mainly that everyone involved has an interest in believing or making others believe that those gains found are big.
Media that invests in aero testing: They must convince their readership that it is relevant, otherwise they just wasted a lot of money and time.
Same goes for manufacturer that invest a lot of R&D in aerodynamics. Often involved external partners that specialize in aerodynamics. Obviously their work is only justified if the outcome is relevant.
Wind tunnels and companies offering other ways to measure aerodynamic drag: obviously more people are interested in buying their services and products if what you measure is significant.
Athletes: Being convinced that you benefit from all the aero testing is a mental advantage.
Consumers: You want to believe that you benefit from that aerodynamic upgrade you spent your hard-earned money on.

So once you are convinced that aerodynamics are relevant (which you should!), it is also beneficial to you to believe those gains are big.

Follow us for the next part where we explore how numbers can be real but inflated at the same time.

: Last year, I wore through a set of road tires all the way to the threads. What surprised me wasn’t just that I had ri...
26/05/2026

: Last year, I wore through a set of road tires all the way to the threads. What surprised me wasn’t just that I had ridden enough to do that again, but how differently the tires aged compared to the 23–25 mm tires I used to ride at a younger age.

Narrow, high-pressure tires would quickly develop a flat spot in the center tread, giving them a noticeably squared-off profile after a few hundred kilometers.

Modern wider tires seem to wear much more evenly. Lower pressures and larger air volume distribute the load better, so the tire maintains its intended round shape for much longer.

The obvious benefit is increased tire life.

But there may be another, much less discussed advantage: aerodynamics.

Your front tire is just as exposed to airflow as your rim. And a squared-off tire with a flat leading edge is probably not a very aerodynamic shape anymore.

Which raises an interesting question:

After some real-world wear, could a well-shaped 30 mm tire end up being just as aerodynamic as a worn 25 mm tire?

: the bicycle industry has established standards that give a very distorted picture when comparing different performanc...
19/05/2026

: the bicycle industry has established standards that give a very distorted picture when comparing different performance gains. For example, aerodynamic gains are often communicated as measured in the wind tunnel at a speed of 45 km/h. Meanwhile, bicyclerollingresistance.com publishes rolling resistance at 29 km/h for a single wheel. Now how do the two compare? In this graph we plotted the gains at different speeds for 7 W savings in the wind tunnel (full aero bike vs. good allrounder) and 4 W published by bicyclerollingresistance.com (Continental Grand Prix TR vs. Continental Grand Prix 5000 S TR). You will be probably susprised to see that at speeds that are relevant for most riders, those 4 W in rolling resistance are worth a lot more than 7 W in the wind tunnel.
Also a fact worth highlighting is that at 15 km/h, a speed at which you are likely in climbing and putting out meaningful power, you still get 4 W of gains from rolling resistance, but just 0.3 W from aerodynamics.

: Today we show why we are often doing the same work multiple times. To achieve the best result, we try different tools...
05/05/2026

: Today we show why we are often doing the same work multiple times. To achieve the best result, we try different tools and different settings. Even though they all seem to do the same, the differences can be quite significant.
The example shown here is quite simple, a profile that tapers at two different rates, with a smooth transition in between. But using native Solidworks tools, we got some waviness in the transition. Instead, we used the blend surface tool of the GW3D AddIn for the primary surfaces, and the xNurbs AddIn for the transition, achieving the smoothness we are striving for.

: Third (and maybe final—tell us if you want more) installment of our CAD design series.This time: the dropout for the ...
28/04/2026

: Third (and maybe final—tell us if you want more) installment of our CAD design series.

This time: the dropout for the UDH hanger. It requires a relatively large, planar circular interface for proper clamping. Our solution is a subtle raised dome that sits just proud of the surrounding surface.

The sharp edge clearly defines the masking boundary for painting, while keeping the overall dropout compact and avoiding unnecessary material buildup.

Swipe through to see how we build it—surface by surface.

: After last week’s post got such a great response, here’s another look into our CAD process.Once the geometry is defin...
21/04/2026

: After last week’s post got such a great response, here’s another look into our CAD process.

Once the geometry is defined - and kinematics sorted (for full-suspension designs) - and all component interfaces are in place, we usually start by modeling the front side of the head tube and the upper end of the seat tube.

These areas might seem simple, but they form the foundation for positioning the outer edge(s) of the top tube. Getting this placement right is key to achieving a smooth, continuous transition between tubes - as you can see in the following steps when the seat tube–top tube connection comes together.

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