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Parlee ESX launched


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The Parlee ESX aero road bike is a completely new model, and Bikerumor’s one of very few entities who have seen the bike in development. Check our factory tour for a look at a very early prototype. It’s been refined quite a bit since then, coming together as one of the best looking (and lightest!) aero road frames we’ve seen yet.

“We’re certainly not claiming to invent the category, but aero road bikes are certainly growing as a segment,” operations manager Tom Rodi told us. “Aero and weight are always a priority. We knew we could make a fast bike because of our triathlon bike, but we wanted to see if we can make something for the road and in the weight class we’re known for.”

Throughout the project, even back when we saw the prototypes, they’ve been testing in the wind tunnel. First, they put it against their own round tube Z5 to see if there was enough difference to justify the effort. They had some help from folks at MIT to interpret the data, and the answer was yes, based on drag and watt savings. For example, at a 10º wind angle at a realistically fast output, they found about a 13 watt savings. The savings were validated across a range of angles and speeds that reflected what normal riders achieve, so they moved forward.

Rodi says there’s always some compromise when developing an aero road bike. The question is, what are you willing to give up? A bit of torsional stiffness to get more aero? Or a slightly less deep tube profile for enhanced comfort?


“The challenge was creating the tube shapes and profiles that delivered both aerodynamics and the ride feel that Parlee’s known for,” he said. “And there’s backlash against the aesthetics of some aero road bikes, so we wanted it to look good, too.”

They also had to think about weight. Some prototypes were actually as low as 800g, but production models ended up a bit heavier because they said “they were just way more fun to ride.”

“We did this with a design we call Recurve, and it’s patent pending,” Rodi said. “The shape is a modified air foil with a rounded front with a reversed curve on the trailing edge that comes back on itself. What’s striking about the design is that it’s obviously aero, but not so deep.

“It delivers the promise of the Kammtail’s aerodynamics but with the torsional stiffness and ride quality of a traditional round tube. We wanted a bike that just plain worked and wasn’t in any way a nuisance to own.”

As proof of that, they decided on using Shimano’s direct mount (two bolt) brakes rather than the hidden TRP direct pull calipers. The latter may have been a bit more aero, but the Shimano’s are much more user friendly. And they’re looking forward to trying the upcoming dual-bolt eeBrakes (spotted on one of Fair Wheels’ show bikes) on them, too. On top of that, the cabling is all fairly straightforward and easy to service.


With their Z5 road bike, they offer standard and tall frame sizes, creating 24 effective frame sizes. The ESX uses a variation of this flex fit geometry: There’s a top cap that nestles into the frame, around the steerer tube, that allows the frame to appear taller and reduce the number of spacers required to fit taller riders. They’ll offer five different frame sizes. The bonus: Their system still allows you to run any stem you want. The pic above shows it without, and below with the spacer.



The seatpost is proprietary, available in 0mm and 25mm offset. It carries the Recurve aero tube shape from the seat tube all the way up to the saddle. The clamp bolt is flush with the top tube.


About the aerodynamics, they’re still determining what they’ll publish. In reality, wind tunnel tests are funny things. Brands can find the angle and speed and other settings where they perform best and use those to tout the product. Some of it’s useful, but in the end, Parlee seems content that their tests validated the concept.

Beyond the unique looks, the frames are light. With a 925g to 950g target weight for a M/L size, that’s only about 100g heavier than their Z5 and very, very light for an aero bike. Their custom fork is about 320g with 300mm uncut steerer. Seatpost is around 185g.


Other quick specs: The bike runs full internal cable/wiring and is electronic/mechanical ready. Tire clearance is good for up to 28c, and it uses a PFBB30 bottom bracket.

Bikes start at $6,500 complete w/ an Ultegra mechanical build. Frameset is $5,400 w/ seatpost, Cane Creek HS and fork. They’ll top out at $10,200 with full Dura-Ace Di2 9070. Enve Composites bars, stems and SES wheel sets are available as upgrades, as are the new Mavic CC40′s and the EE Cycleworks Direct Mount brakes. The base spec of all the complete ESX’s in the US is 3T Team Stealth Bar and Stem, HED Ardennes+ Lt Wheels and corresponding (full groupsets) i.e. Ultegra Di2 builds get full Ultegra parts including chains and cassettes.

It’ll come in their usual matte blacks and will be offered through their custom paint program, too. Rodi says the extra real estate on the aero tubes is already letting them do some pretty sweet custom paint schemes that just wouldn’t look right on round tubes.

Edited by gummibear
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