Race-Oriented Brand Goes Full Squish: Cervélo ZFS-5 GX Eagle Mountain Bike Review

Cervélo road bikes have been lust-worthy for decades. Its road models have been at the front of the pro peloton, garnering top podium spots at the most prestigious races, like the Tour de France. Given the brand’s lauded history, the Cervélo ZFS-5 came with high expectations.

I’m a roadie at heart, so to see the Cervélo name affixed to its first fat-tire, full-suspension mountain bike was a bit of a cultural shock. But a few miles down the trail, I knew that all the knowledge and experience the brand has amassed by building some of the most demanded road bikes is part of the ZFS-5 DNA.

I tested the Cervélo ZFS-5 for 6 months on the hardpack, rocky, tight, and ledgy cross-country trails in my Central Texas area. On most of these rides, I was at the limits of my aerobic fitness; there were no casual “cruises.” The bike was the vessel for fairly serious training as I readied myself for an event in the fall.

In short: Cervélo didn’t disappoint with its first attempt at a full-suspension mountain bike. The race-oriented ZFS-5 GX Eagle gobbled up singletrack with a ride that balances pedaling efficiency with suspension action. The frame also possesses a lively feel that is a rarity in carbon race bikes. And the platform is ripe for upgrades, making the bike one to keep as you gain fitness, speed, and skill.

Cervélo ZFS-5 GX Eagle Mountain Bike Review

Main Specifications of the ZFS-5

My test bike was Cervélo’s entry-level, non-electronic SRAM GX Eagle version of its 100mm race-oriented ZFS-5 offerings. It has a component selection that renders an MSRP of $5,000, which is $1,250 less than the lower next rung up, which has SRAM GX Eagle AXS Transmission. And the GX Eagle model is less than half the cost of the chart-topping, $10,700 ZFS-5 XX SL AXS. All three models feature RockShox SID suspension.

The ZFS-5 lineup contains one 120mm option, the ZFS-5 120 XO AXS. As can be guessed, it has SRAM XO Eagle AXS and is the only version with FOX suspension. It sells for an MSRP of $8,700.

Cervélo has four frame sizes: Small, Medium, Large, and Extra Large. The frame internally routes cables and hoses through the top bearing of the headset. It has space for a water bottle on the down tube and seat tube.

Astute cycling industry followers will note that the ZFS-5 frame looks an awful lot like the Santa Cruz Blur frame. This isn’t a coincidence; the same parent company owns both brands and thus can share resources. But the ZFS-5 isn’t just a Blur copy.

One significant difference is the head tube angle is slacker on the ZFS-5. But the Blur was a good place to start in the development of Cervélo’s full-suspension race rig.

Suspension

A RockShox SID SL Select fork with two damping settings manages front suspension duties. Cervélo uses a RockShox SIDLuxe Select+ to handle the back end, and it has three damping settings.

Drivetrain and Wheels

Cervélo puts the SRAM GX Eagle mechanical drivetrain aboard the ZFS-5 GX Eagle, with a 32-tooth chainring and a 10-52 tooth cassette.

A threaded bottom bracket keeps the aluminum crankset spinning, which drives Race Face ARC Offset 27 aluminum alloy wheels. Maxxis Recon Race tires in a 2.4″ width hinted at a cushy ride for a race bike.

Brakes and Other Parts

Deceleration duties go to the SRAM Level Bronze Stealth four-piston system. Curiously, Cervélo puts a Race Face Aeffect Alloy bar with a Turbine Alloy Stem in a 35mm bar/clamp diameter. This seemed overly beefy for a 100mm bike and visually stood out against some of the svelte frame tubes.

Another puzzling specification was the lack of a dropper post. A Race Face Ride XC seat post supports a house-branded saddle. The ZFS-5 was the first mountain bike I’d tested without a dropper in quite a while. I was a little worried about dropping off certain ledges, regardless of how well I knew them.

Our Cervélo ZFS-5 GX Eagle in a large weighed 26.5 pounds with XTR pedals set up tubeless.

The Cervélo ZFS-5 on Trails

I expected a lot from this bike. I’ve always viewed Cervélo as a performance brand. It has won countless professional road and cyclocross victories, lately under the Visma-Lease a Bike squad. And the frames always gave me the impression that marketing angles were far down the design parameter list.

Chassis Feel

I wanted to go fast on this bike, so I went to the trails I’ve ridden the most. Since the mid-’80s, I’ve ridden Austin’s Barton Creek Greenbelt and all its permutations countless times.

Ten minutes down the trail, I felt remarkably comfortable cutting my usual lines on the Cervélo ZFS-5. The bike felt “neutral” to me. I didn’t have to compensate away from the way I naturally wanted to ride a CX-oriented machine.

I felt that I was sitting “in” the bike and not “on” the bike and that I had a lot of leeway to remain “centered.” It’s so cliché, but the chassis felt like an extension of my body.

Another attribute of the chassis that was almost immediately apparent was a less harsh feel than on other carbon race bikes I was testing at the same time. It reminded me of certain road and gravel bikes, like the Specialized Aethos and S-Works Crux, that have an unexplainable, mesmerizing feel. This was especially felt on the fastest sections of my trail networks.

These straight shots allow me to hammer the tallest gear but are littered with small, embedded stones. On other bikes, the vibrations can be super harsh, even through the pedals. The Cervélo was a tad bit kinder to my bones.

Pedaling Efficiency

Turning every bit of effort into forward motion is paramount in a race bike. And the Cervélo ZFS-5 did an admirable job.

The frame was laterally and torsionally stiff, as a race bike should be. But relative to other high-end race bikes I’ve been testing lately, it felt less single-minded. In no way did it feel like I was robbed of any power; it just didn’t feel like pedaling a block of carbon. It had a lively reaction to pedaling forces, akin to the less harsh feel I described above.

For the simplest rear suspension designs, the shock was super resistant to squatting under a hard pedaling. I felt this the most when I was applying higher-torque, lower-cadence efforts while seated. The downside was that I had to thread the correct line on rougher sections to avoid rear-wheel hop under load, but I feel that way about most flex-stay bikes.

Cervélo ZFS-5 Suspension and Handling

Both ends of the ZFS-5 felt supple in the initial travel over a smaller chunk. The tires felt super planted at high speed over such terrain, which gave me confidence that they would stick when required. I especially felt the SID SL Select was remarkable here, given its lower cost relative to other suspension forks I’d ridden.

As the terrain got rowdier, the fork and shock ramped up at a predictable rate and still felt supple for a 100mm race bike. Crossing dry creek beds strewn with rocks at speed felt as planted as I could expect from such a bike. Combined with the lively frame feel, I felt remarkably “light” through these sections. Again, I was impressed, given that I was aboard the most affordable ZFS-5.

Climbing while seated was efficient as long as I kept my body positioned correctly. I had to keep weight on the rear tire and also maintain weight on the front to keep it down and tracking, the same as on other short-chainstay race-oriented bikes.

Descending was impressive for a race rig. The “sit in and not on” feeling this chassis delivered gave me confidence as I navigated twisty descents that required weaving between large boulders. For a 100mm CX race bike, going downhill on the Cervélo ZFS-5 was a hoot. It felt like it had more suspension travel than it did.

When dropping off the bigger ledges, both ends felt admirably supported. Again, the ramp-up in damping was predictable, and I never felt like I had to stiffen up my body to be ready. Resistance to bottoming was good, and if I did bottom out, it wasn’t harsh enough for me to bother with cussing.

In the end, for a race bike, I felt the ZFS-5 had an ideal balance between having an active suspension action and providing an efficient pedaling platform. There are more efficient bikes, and there are more active ones, but this bike hit the sweet spot for me.

Other Performance Opinions

Given that our version of the ZFS-5 was the entry-level model, I set my expectations appropriately.

Shifting

First, this was mechanical shifting, and I admit that I hadn’t tested a bike with a derailleur cable for a long time. So, there was a period of adjustment of both my shifting habits and my base level of performance expectations.

For a cable-actuated system, I didn’t have much to complain about. After the initial cable-stretching and rechecking of the B-tension screw (with the SRAM Chain Gap Tool) and limit screws, the shifting was crisp and reliable for a mechanical groupset.

I didn’t “baby” the rear derailleur just because it wasn’t electronic. I shifted with the same timing as I do with electronic systems.

Shifting to a lower gear ratio didn’t produce any drag between cogs like I expected. The ramps in the cogs did a great job of lifting the chain up, even to the massive 52-tooth bailout gear. And shifting under load to a larger cog didn’t create the noise and drag of older systems. Those days are gone!

Going up to a larger cog didn’t require an inordinate amount of pressure at the shift lever. I just had to remember that it was mechanical, and everything was fine. No, it’s not the set-it-and-forget-it button push of AXS. And yes, I had to carry through the lever pressure until the shift was complete. It is not electronic, and in that light, it passed the test.

Shifts to smaller cogs did produce a louder “clunk” than I’m used to with SRAM AXS, but the accuracy or reliability wasn’t affected. I tried to find a reason not to like mechanical shifting, but I had zero complaints. I was impressed, especially given the much more affordable price of the GX Eagle wares compared to any AXS setup.

Braking

I would love to rave about the SRAM Level Bronze Stealth brakes, but they were just adequate, in my honest opinion. If the ZFS-5 GX Eagle were mine, the brakes might be the first thing I would upgrade.

After the bedding-in period, I expected the vague initial bite to disappear. Although much improved, it was still a little vague, making the light scrubbing of speed a little bit of a guess. This did improve as time went on, but it still wasn’t up to par with other units.

The modulation and progressiveness were also a little “soft.” The lever feel wasn’t as crisp as on other units, and the rise in power was less linear. I adjusted my lever pull as the bike reacted to the brakes more than usual. I didn’t hit the correct lever actuation on the first try much of the time, as my perception of pad pressure wasn’t as crisp.

But the Level Bronze Stealth four-piston calipers had great power when I really needed it. For as much power the calipers had, the lever pull was pleasantly easy. And on the longest descent on the Greenbelt, they resisted fading well.

In the end, the performance for a $165 brake was good. I’m just spoiled with much more expensive units on most of my testers, and I’m quite sensitive to braking.

Other than the above, the rest of the bike was unnoticeable, which was a good thing. The wheels remained true throughout the testing period, and the trails here deliver blows to wheelsets from every angle. The cockpit was fine; nothing stuck out enough to complain. I even fared well with the house-branded seat.

Weight

I didn’t want to include this section at first, as the ZFS-5 GX Eagle has a respectable weight for its price and level of componentry. However, I did feel the extra mass compared to the other bikes. Every action took a little bit more input a little earlier. This is in comparison to race bikes that cost at least $4,000 more.

And it is just a feeling. Light bikes feel, well, light. They feel more agile, accelerate a bit quicker, and are more responsive to everything, including braking. A heavier bike can feel more planted and stable at times, but for racing, these feelings are combined with efficiency, and when a podium spot is in the sights, light is right.

Finally, I missed having a dropper post. If I bought this bike, I wouldn’t leave the store without getting one.

Conclusions on the Cervélo ZFS-5 GX Eagle Mountain Bike

The most significant things that struck me about the ZFS-5 GX Eagle were the feel of the frame and the price point. The lively-feeling frame struck the ideal balance between suspension activity and pedaling efficiency, a welcome rarity in a race bike.

Combine these with the $5,000 MSRP (I have seen it on sale this year for significantly less), and you have an ideal entry point to a true race machine.

But what is even more exciting to me is this bike is prime for upgrading as a rider’s speed, skills, and stoke progress. The frame is a rock-solid start, and the efficiency and feel it possesses are not bolt-ons.

Every small complaint I had about this bike was related to an easily upgradeable component outside of the spend. This includes the issue of weight, as every component upgrade will drop mass.

If you want a race-ready chassis that you can stick with as you rise through the ranks, the Cervélo ZFS-5 GX Eagle is an ideal base. Remember, the frame is the foundation and the single largest contributor to performance, and this bike has the goods to carry you as far as you want to go.