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The new Cervélo S5 is smoother in the wind and in its setup

The flagship aero road bike gets simplified, a little, sheds some weight and goes faster

Cervélo S5 Photo by: Nick Iwanyshyn

The new Cervélo S5 has been a terribly kept secret by the once-Canadian company. The pros of Jumbo-Visma have been riding, and winning, on this bike since early this season. Now, Cervélo, which is owned by the Dutch organization Pon Holdings, has made it official: its new aero road bike is here.

What took so long for the release? Well, all the challenges that have been affecting bike production throughout the past two years. Cervélo wanted to make sure it had bike in-stock at launch.

Subtle but important changes at the (kinda controversial) V stem of the Cervélo S5

When the previous S5 was announced in 2018, it came with its head-turning, and occasionally polarizing, V stem. The design fulfilled a few roles. It allowed hydraulic brake hoses and shifting cables to run internally from the bars, through the stem and into the head tube with fairly shallow bends. With a more conventional bar/stem combination, the cables have to make a pretty sharp turn into the head tube. That bend can have a negative effect on mechanical shifting performance. To make sure that mechanical shifting would work well, engineers, such as Scott Roy, looked to the V stem layout. “Truthfully, it was scary making that stem,” Roy says. “It was kind of uncharted. We were going through testing and development. We were even over-testing it. We had it with the team for a long time, but we needed to make it full-proof.”

Cervélo S5 V stem
The V stem on the Cervélo S5. Image: Nick Iwanyshyn

The team nailed the functionality of the stem, but there was a hitch when it came to adjustability. The bike came slammed: great for the pros or the vain, but not practical for most of us. Dealers had to have the right bolts and spacers on-hand to set up the bike for customers. If you bought an S5 used, either you’d hope you had the same fit as the bike’s previous owner or you’d have to chase down the right bolts and spacers elsewhere.
With the new S5, the bike ships with one set of bolts and 30 mm of spacers. Sounds like a small thing, but it really does make things easier. When I assembled the bike, I simply threw on all the split spacers, which fit around the brake lines, and twisted in the three bolts. If I want to make a change, it will be a cinch.

The irony with the V stem is that while it was first designed, in part, to make sure mechanical shifting was smooth, that feature is no longer needed. The new S5 frame is for electronic shifting only. The move makes sense as top-end drivetrains are very battery-centric now. (Shimano’s lineup is electric all the way to 105 now.) Cervélo was able to redesign the dropouts of the S5 and a few other shapes because of the electric-only drivetrain compatibility.

Whether you dig the V stem of the S5 or not, the company is standing behind it. It’s part of the bike’s identity. And, of course, it provides an aero advantage, which you’d expect from an aero road bike from Cervélo.

Cervélo S5 stack
This Cervélo S5 comes with 30-mm worth of spacers: two 7.5-mm-wide spacers and three 5-mm-wide spacers. You can adjust the tilt of the bars with the bolts on their underside. Image: Nick Iwanyshyn

More adjustable bars on the Cervélo S5, new seatpost

The previous generation of Cervélo S5 used wedges to adjust the tilt of the bars. On the new bars, you can simply loosen four bolts, tilt the bars from zero to five degrees, and then snug up the fasteners.

Most new S5s come with a new seatpost with a 15-mm offset. This post replaces the 25-mm offset on the previous generation of bike. If you want the longer, more-aggressive fit, you can still get the old post.

Another stab at the bayonet

The bayonet fork, with its “steerer” sitting in front of the head tube, is back. The old bayonet had an alloy topper that closed the fork around the head tube. (There’s a tension rod inside to help with the connection.) That topper is now gone. The fork is one piece. “We had tried to make a one-piece fork originally,” Roy says. “There were a few of us, constantly, in our down time [after the 2018 launch of the S5], between other bike launches, rehashing the idea of getting the fork to one piece. The manufacturing of that new fork was quite difficult and figuring out how to do that with the factory took a long time.”

In some circles, controversy followed the older S5. There were claims that the steering stop within the head tube, which kept the bars from twisting too far to the left or the right, could damage the head tube itself. Roy says he and his team tried to replicate the issue, but they couldn’t. Still, they’ve redesigned the stop. The old stop was a hard piece that butted up against the inside of the head tube itself. The new setup features a stop with rubber bumpers that come up against an alloy piece bonded into the lower head tube.

Cervélo S5 bayonet
The Cervélo S5 has a one-piece carbon bayonet front fork. Image: Nick Iwanyshyn
Cervélo S5
The Cervélo S5 has clearance for 34-mm-wide tires. This tire is 28c. Image: Nick Iwanyshyn

Compensation triangles

For 2021, the UCI changed some of its rules regarding tube shapes and dimensions on bikes. Remember, the UCI wants to keep bikes looking, well, bike-y, so it sets the parameters for various elements of frame design. With the recent set of changes, the organization allowed for compensation triangles in four places: between the top and seat tube, between the seatstays and seat tube, between the chainstays and seat tube, and between the down tube and the seat tube. The sides of these triangles that are next to a tube or stay can have a maximum length of 8 cm.

So what’s with these compensation triangles? They add more material that increases the surface area of the frame allowing for more of a sail effect as the bike moves down the road. The effect keeps airflow attached to the frame at yaw angles above zero degrees. Then, it’s a bit like a sailboat tacking into the wind. In short, those little triangles, while small, do boost the frame’s performance, making it faster.

On the new Cervélo S5, there’s a compensation triangle between the top and seat tube. Also, the material above the bottom bracket counts. While you can’t technically say there’s a triangle going between the top, head and down tube (too many sides!), there’s some of the same principles of compensation triangles at work. The UCI says that from the front of the head tube—or in the case of the S5, the part of bayonet fork in front of the head tube—to the open side of the, uh, compensation quadrilateral, can be a maximum of 16 cm. The new Cervélo S5 is 10.5 cm from the front of the bike to where the top/head/down tube reinforcement zone ends.

The company says it’s reduced drag on the bike by 65 g.

Cervélo S5
One of the Cervélo S5’s compensation triangles sits between the top and seat tube. Image: Nick Iwanyshyn
Cervélo S5
The material between the seat and down tube boosts the Cervélo S5’s aerodynamics. Image: Nick Iwanyshyn

With all that new surface area on the frame, is it heavier?

No. Cervélo says that with the one-piece fork and some of the simplification that it’s achieved at the front end, it was able to reduce the weight of the S5 by about 53 g.

New Reserve 52/63 wheels

The Pon Holdings family tree goes like this: the Dutch company acquired Cervélo in 2012 and Santa Cruz 2015. Reserve wheels, which was founded by engineers from Santa Cruz, was formed in 2014. It’s part of Pon, too. In 2020, Reserve launched its first sets of road wheels with the help of Cervélo. The Reserve/Cervélo collaboration continues with the new 52/63 wheels. Those numbers indicate rim depth: 63 mm in the back, 52 mm in the front.

(If you ask me, the deeper rear rim/shallower front rim you see on bikes chasing aero gains is more “mullet” than 27.5” rear/29” front mountain bikes. The mullet haircut, or la coupe Longueuil, has more hair at the back and is shorter at the front. A mixed-wheel size mountain bike has more material—the metaphorical hair, if you will—in the front. The road wheels have more material in the back. And, the mix of rim sizes on aero road bikes lets you shave off seconds from your overall times. For an MTB with mixed wheels, I suggest we call it A Flock of Seagulls. But I digress.)

Other dimensions include a 25.4 mm internal rim width and 34 mm external on the front. The rear has a 24.4 mm inner rim width. In general, the front rim is wider and shorter, while the rear is narrower, taller and asymmetric.

Engineers not only looked at how the wheels performed when they were hit with laminar flow air—think of a smooth flow of air hitting the front tire or the head tube—they also looked at turbulent flow. They’ve mapped out turbulent-flow intensities. Roy says Turbulent 1 is like mild gusts in an open field. Turbulent 2 is more blustery. Roys describes Turbulent 3 as Kona.

Roy and his team found the wheel shapes performed well in both laminar and turbulent conditions. They were able to identify and then better manage the stall point on the front wheel. “A really good way to visualize it,” Roy says, “is with a constant crosswind. With that crosswind, you self correct. You can feel the wind and adjust for it. What these wheels are really good at is when that wind drops off, you’re not, all of a sudden, pulled to the side. Once that crosswind drops off, you’re not thrown the other way. It’s a real mellow correction. The new wheels ride like shallower profile wheels in windy conditions.”

The rim shapes work best with 28c tires. The bike has clearance for 34-mm treads.

Reserve rear wheel
Both Cervélo and wheelmaker Reserve collaborated on the new Reserve wheels. The rear has a rim depth of 63 mm. The front is 52 mm. Image: Nick Iwanyshyn

Availability of the Cervélo S5

Maria Benson, director of product management at Cervélo, says the new S5 is available now. If you can’t get your hands on one at launch, don’t worry. The company will have a second round of production and delivery in August.

The Canadian prices of the new Cervélo S5

Cervélo S5 build Canadian price
Shimano Dura-Ace Di2 $16,250
SRAM Red eTap AXS $16,250
Shimano Ultegra Di2 11,250
SRAM Force eTap AXS $11,250
S5 frameset $6,900
Cervélo S5
The Cervélo S5 with SRAM Force AXS drivetrain. Image: Nick Iwanyshyn
Cervélo S5 crank
This Cervélo S5 comes with a 48/35-tooth SRAM Force crankset outfitted with a power meter. Image: Nick Iwanyshyn
Cervélo S5
Cervélo S5. Image: Nick Iwanyshyn
Cervélo S5
Cervélo S5 top tube. Image: Nick Iwanyshyn
Cervélo S5
Cervélo S5. Image: Nick Iwanyshyn