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Reynolds 46 Aero review

Reynolds 46 review
21 Oct 2015

Is the Reynolds 46 Aero the ultimate all-round wind-cheating wheel in its clincher form?

Aero wheels are big business. Pioneered by Steve Hed in the 1980s, capitalised upon by Zipp in the 1990s and exploited to full effect by Simon Smart with Enve in the 2010s, recent years have seen the blunt or snub-nosed rim profile dominate the scene. 

It’s easy to think that such rim profiles are as fast as things can get, yet Reynolds’ director of technology and innovation, Paul Lew, would argue otherwise, and with these 46 Aeros he has stuck resolutely to the teardrop profile associated with aeroplane wings. He calls it Dispersive Effect Termination, or DET.

Reynolds 46 rim

The (very oversimplified) theory goes like this: lift is generated when wind hits a certain rim shape from a certain angle (yaw). Lift is a force that has a component in the direction of travel, and thus opposes drag, which operates against the direction of travel and increases with speed and yaw angle. Aero wheels aid a rider by generating a lift force with a component in the direction opposing drag. 

‘Rims don’t generate lift by you pushing them through the air, but rather by air blowing on them in the form of wind,’ says Lew. ‘Blunt profiles generate a lot of lift but need a lot of wind, above 30kmh, to do so. But in the absence of wind, that profile generates a lot of drag. Wheels like the Zipp 303 are high-lift, high-drag, and have been designed to perform well at 40-50kmh. The problem is that most of us don’t ride bikes that fast.’ Lew’s solution was to design a low-lift, low-drag wheel, which is where DET comes in.

‘The DET rim is designed to perform in lower-speed conditions,’ says Lew. ‘Because it’s a low-drag rim it performs very well when the wind is gentle, and because it produces low drag, when the wind starts to blow it doesn’t require as much lift to oppose that drag.’ 

The upshot, says Lew, is that the DET shape of the 46 Aeros provides a bigger ‘sweet spot’ than its competitors. Lew believes it benefits the rider for longer throughout a range of wind speeds and yaw angles before it stalls and ceases to be effectual. Got all that?

The paper  

For those who care to know more, Lew has published a white paper on the subject online, which makes for some mind-boggling reading (while you’re at it, Google his Black Hole wheel from the 1990s). My C in A-Level physics prevents any further analysis of DET, so I’ll just report on how the 46 Aeros felt and, more importantly, how they affected my Strava profile.

Reynolds 46

As with any wheel test, I swapped the 46s onto a known bike that was previously kitted out with lightweight box sections. I wasn’t expecting the same zing from low-speed accelerations when rolling on the 46 Aeros, but I was pleasantly surprised. For a wheelset weighing 1.5kg the 46s picked up incredibly well, if with some complaint over uneven road surfaces. 

My first few rides were relatively calm in terms of wind, and it was during these that Lew’s scientific claims seemed to ring true. The bike I was on – a traditional round-tubed machine – was transformed from noble plodder to something resembling a mid-chase Champion the Wonder Horse. That is to say, it was quick. Of course the speed of a bike is dictated by the ultimate power you can generate but, as several new Strava PBs revealed, that power was being used far more efficiently when injected into the 46 Aeros. The effect did seem less when riding in windier conditions, but the wheels still handled well, even when it was gusty.

What’s in a name?

Lew, or at least the marketing people he works with, are no slouches when it comes to acronyms. Joining DET is ISH, integrated step hook; BWI, brake wear indicator; CR6, carbon rim 6; and CTg, cryogenic glass transition.

Like DET, none of these terms is self-explanatory. BWI means a red marker strip has been embedded in the brake track, which reveals itself if the carbon gets excessively worn. CR6 means six different carbon fibres and layups have been used in six crucial areas of the rim. ISH means the edge of the rim has been shaped to create a channel between the rim and tyre, something Lew says helps smooth airflow. CTg refers to the high temperature resin used to better cope with heat from braking.

Of all these, it’s the CTg that will mean most to riders. Braking on the 46 Aeros in the dry, using Reynolds’ own Cryo-Blue brake pads, was superb. The brake tracks are even, giving no shudder through the frameset, and the bite of the pads was firm and progressive, making for powerful, well-modulated braking. Even in the wet the 46s are, for carbon rims, half decent, although I would question how long the soft durometer rubber pads would last if exposed to repeatedly wet and gritty riding. They’ll still never compete with the milled aluminium surfaces found on some wheels, but at least they are predictable and reliable enough to feel safe on wet descents.

It’s hard to find many criticisms, but one area where the 46 Aeros do seem to be lacking is in dimensions. A rim bed width of 16mm just seems a bit narrow and a bit dated compared to the recent flood of 17mm-plus widths, the problem being that even 25c tyres inflate to little more than 23mm as the beads sit closer together, and it’s this smaller tyre volume I feel is culpable for a fairly harsh ride quality. But because riding the 46 Aeros is just such a rapid experience, and because they handle themselves so well, I’m just about able to forgive them.

Reynolds 46 Aero Clincher
Weight 1,505g
Rim Depth 46mm
Rim Width 26.2 ex, 16mm int
Spoke Count 16 front, 20 rear

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