Weight Weenies

Haven't seen any discussion of Campag's announcement of its Bora WTOs: https://www.campagnolo.com/UK/en/CampyW ... ora_wheels

60mm wheelset and a 77m front only, with a new rim profile optimised for aerodynamics (WTO standing for Wind Tunnel Optimised).

A couple of things immediately pop up:
- what do these say about Campag's faith in the classic 50mm Bora depth, and the Bora profile, at least from an aero point of view? Not much?
- these are to be released as two way fit with tubeless as the preference: "Contrary to popular belief, the tubular tire is the worst performer" ( ). What does this say about the medium to long term future of the classic Bora tubular range? At 1550g for the WTO 60 wheelset, they are a long way off the weights of Bora 35 or Bora 50s.

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There was some discussions in the Campy 12-speed thread. I don't see the new wheels as replacements to the Bora 35 and 50 wheels. I think the WTO wheels were created in part by requests from the World Tour sponsored teams for the flatter stages. For climbing stages these teams will continue to use the 35 and 50 wheels in the tubular format. For the record the WTO rim profile is a modified NACA profile. The NACA is a tried and trued shape, one that has a good balance between aerodynamics and weight. Non-NACA rim profiles (i.e. Zipps, Enve, etc.) may have better cross-wind stability at high yaw angles however they are heavier due to more materials used to create the U profile. This is also why the Lightweight Milenstein uses a modified NACA profile and not a U profile.

Personally I won't be getting the WTO wheels. I already have the 50 and 35 wheels. The terrain here is too hilly and windy for a 60mm wheelset. For daily riding I'm using a 35 front and a 50 rear.

For anyone who wants to learn more about aero wheels, the best educational material by far is this video by Hambini. According to Hambini the single most important aspect as it relates to aerodynamics is the rim depth and not the rim profile! And he used CFD analysis to prove his point.

https://www.youtube.com/watch?v=BUih_emc54M

Interestingly the new Bontrager Aeolus wheels went back to the NACA aero shape, not too different from the Bora WTO. They claimed they analyzed 10,000 different rim profiles.

https://www.bikeradar.com/us/road/news/ ... ces-52012/

The round V-shape is not as proone to crosswinds as the torodial shape they used before. But if crosswind stability is no. 1 on your list, you should take Reynolds teardrop shape. They do have a little more drag in crosswinds too, though.

But in general: you can achieve 15 watts with Ksyrium vs. Zipp 808 at 45km/h, where overall 450 watts are needed - so a 0,5km/h difference at max. Differences between wheels with the same rim height are tiny, even when using different shapes.

I was excited when I saw these as i'd really wanted a 60-65mm deep wheel since getting my Bora 50's and realising the wind was not a problem! But am also disappointed by the weight. There is no real difference between the Bora Ultra 35's and 50's and my 50's came in at 1420g so I was hoping these would be under 1500. Also surely they chould have carbon hubs.

The Bora One 50s are about 1,470g. So a gain of 80g is not bad considering the WTO is both wider and deeper than the One 50s. Carbon hubs would cut another 50g but it’s assumed that those riding the WTO would do so on flatter terrains.


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When are these wheels suppsed to become available? I haven't even seen them available for pre-order yet, nor any info on pricing.

pdlpsher1 wrote: ↑

Mon Apr 23, 2018 11:21 pm

Non-NACA rim profiles (i.e. Zipps, Enve, etc.) may have better cross-wind stability at high yaw angles however they are heavier due to more materials used to create the U profile.

Actually, tests indicate that U shape like Zipp is better in lower aerodynamic drag at high cross-wind angle, not stability. U shape seems to be faster in crosswind, Stable-y low drag across multi wind angle. But not really more stable interm of handling, especially with wide tires.

I think Enve (especially rear of 4.5 AR Disc) looks similar to NACA too.

Carbon needs volume to reduce wall thickness (therefore most stiff superlight frames have big round downtubes). The torodial WTO shape will be lighter at the same height and width than the round V-shape they used before. The teardrop shape is the heaviest, as more material is needed to make it stable.

And the NACA (National Advisory Committee for Aeronautics) developed shapes for aircraft wings based on the teardrop shape. So, actually there is not the NACA shape but many different ones. There are also curved shapes to cause lift.

For best crosswind stability the rim has to have a really sharp V-shape like a teardrop.



Bontrager measured the crosswind stability of their wheels compared to Enve and Zipp:

Aeolus XXX 2 | 5 Nm
Aeolus XXX 4 | 6 Nm
Aeolus XXX 6 | 8 Nm
Enve 2.2 | 4 Nm
Enve 4.5 | 7 Nm
Enve 6.7 | 8 Nm
Zipp 202 NSW | 5 Nm
Zipp 303 NSW | 7 Nm
Zipp 404 NSW | 8 Nm

Reynolds Aero 58 and 46 were both tested 1 Nm by Tour Magazine, Zipp 404 FC were 7 Nm...

Triathlon Magazine even called the Reynolds Aero 80 very stable in strong crosswinds.

The new WTO will save a few watts in high yaw angles but won't be more stable in crosswinds.

Reynolds also tried a toridial shape on their Strike wheels with a swirl lip generator to reduce side force: https://support.reynoldscycling.com/tec ... -generator Doesn't work.

How come Lightweights are probably the worst handling rim in gusty conditions out there? I don’t know why, but they are. Maybe the cross section of their spokes adding significantly to the surface area versus flat steel spokes?... the big flange at the hub? the thin flat shape? I don’t have the answer but sure do notice a big difference in gusty conditions on 47-52mm Lightweights compared to even something like a Bora which isn’t particularly toroidal shaped at all, yet the Bora is so much more stable in the same conditions, even the older pre 2015 narrower version.

Beaver wrote: ↑

Thu May 31, 2018 9:26 pm

For best crosswind stability the rim has to have a really sharp V-shape like a teardrop.

Bontrager measured the crosswind stability of their wheels compared to Enve and Zipp:
.
.
.
Reynolds Aero 58 and 46 were both tested 1 Nm by Tour Magazine, Zipp 404 FC were 7 Nm...

Triathlon Magazine even called the Reynolds Aero 80 very stable in strong crosswinds.

The new WTO will save a few watts in high yaw angles but won't be more stable in crosswinds.

Side force isn't the same as crosswind stability - side force for any wheel fluctuates as airflow breaks away and reattaches. The frequency and sharpness of that cycle is also important to how the wheels feel and handle. A greater side force that varies (comparitively) slowly and smoothly can feel more stable than a lower total side force that varies rapidly and suddenly.

This post is from my experience and may contradict others...

The teardrop shape helps with turbulence in the wake I think so should be fast at 0 degree if it were deep enough (which they rarely are, = low area).

Toroidal shape allows for airflow around the front and back of the rim to have similar detachment and thus it's more stable at crosswinds as a result. Toroidal rims have a relatively large area so they see those effects more. The shape helps to keep it under control though.

I think the reason lw rims HAVE BEEN garbage is because they were pure V=shaped and very narrow as well. Put a 25mm tire on there and you have a terrible recipe against crosswinds. Ridiculous detachment front/back. Relatively large area, not mentioning the spokes.

My 88mm toroidal rims are very stable and I ride them every day. Never felt a wind gust I couldn't handle.

Calnago wrote: ↑

Thu May 31, 2018 9:51 pm

How come Lightweights are probably the worst handling rim in gusty conditions out there? I don’t know why, but they are. Maybe the cross section of their spokes adding significantly to the surface area versus flat steel spokes?... the big flange at the hub? the thin flat shape? I don’t have the answer but sure do notice a big difference in gusty conditions on 47-52mm Lightweights compared to even something like a Bora which isn’t particularly toroidal shaped at all, yet the Bora is so much more stable in the same conditions, even the older pre 2015 narrower version.

It's the spokes. My Shamal C17's are way harder to handle in the wind than my Zonda C17's - the only difference is the spokes. (OK, I know the rim is slightly more square on the Zonda's, and the hubs are different, but these differences are tiny).

Tangent: and the Shamals are wayyyy stiffer than the Zonda's. No matter what anyone tries to say about Zonda's being 90% as good, they are basically 1/3rd as good... and the price reflects this.

I’ve ridden the Shamals. They’re fine. Not even close to what you experience on Ligthweights. Have you ridden Lightweights in any kind of gusty conditions, descending or otherwise, doesn’t really matter. If there’s a gust they will catch it.

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I suppose that the low weight of the Meilenstein also contribute to reduce their stability in crosswinds etc...