Felt’s Z4 Disc is the brand’s entry into the disc-equipped endurance road bike category – that new platform of choice for sportive and gran fondo riders – but shouldn't be discounted by those wanting a racier ride.
Boasting full SRAM hydraulics and the American brand’s wide-ratio WiFli gearing, the Felt Z4 could be the ideal ride for those wanting to spin up mountains with all-day comfort and descend with rotor-inspired confidence.
- Highs: Stiff frame with decent damping, perfectly specced for hilly terrain, wide set-up options
- Lows: Discs can rub, wheels a bit heavy, compact gears spin out at speed
- Buy if: You want to tame mountains without giving away racing performance
Related: Felt Z4 Disc Horse for the Course first ride impressions
Ride and handling: comfy and confident
The Z4’s UHC Performance carbon frame is comfortable without feeling soggy. It’s not the most cushioned bike in the endurance road class, but aided by 25mm rubber and amply padded bars, road buzz is efficiently dissipated to give a generally smooth ride so your hands won’t jitter to the point of irritation. The upside to the bike not giving away bags of stiffness is that despite it's place in Felt's 'endurance' range, it still feels racy with superb power transfer.
The Z4 handles beautifully and the WiFli gearing's massive range means any mountain is conquerable
Compared to Felt's AR's range, the Z4 has a marginally slacker head angle, a taller head tube and a longer wheelbase. Combined with the ergonomic bars and sticky Mavic tyres, controlling the Z4 is predictable, stable and accurate. To say that it's simple to keep the machine in check is unfair as regardless of riding conditions or the twistiness of descents, it's not ever come close to the point of straying out of control.
Switching lines mid-corner, dodging potholes at the last second; breezing around hairpins – it all feels easy. This sounds a bit dull, but its precision – especially on downhills – inspires the confidence to really push it, never failing to make riding enjoyable.
That goes for taking on climbs too. No matter how slowly you’re forced to tackle steep gradients, there’s no twitchiness in the steering. It remains calm and under control, yet ready to respond instantly should you need you tweak your line to the smoothest bit of tarmac.
Its stiff, compact frame converts each turn of the SRAM Rival compact crankset into steady upward momentum. The beauty of the SRAM WiFli gearing’s wide range (up to 34t x 32t) means you can conserve energy and spin away all day over all but the most severe gradients. Get out of the saddle and the Z4 leaps up hills with no sense of flex from frame, wheels or bars.
That’s not to say it’s a mountain goat in terms of weight – our 54cm size Z4 comes in at 8.55kg. That’s not staggeringly light for a machine of this price, and while you do feel that weight a bit while climbing, it’s not heft that’ll hold you back. There’s also upgrade potential with the wheels and crankset if you’d like to lighten the load down the line.
Central to the heady feeling of control the Z4 offers are the SRAM hydraulic disc brakes, which aren’t scarily sharp, but work with powerful efficiency. They save hand-ache on longer descents, stop far better than rim brakes and add to the fun by letting you brake later into corners with the confidence that you’re not going to lock the back end up.
The disc brakes offer great performance – it's hard to go back to calipers after trying them
The only downside is that on dusty or vaguely damp roads, they do have a tendency to scuff along noisily, only quieting again once the rotors and pads shed the grime. It is an annoyance, but the undiminished braking performance is definitely worth it overall.
If you’re looking for a flat-out, flat-back race machine, then the Z4 disc can also accommodate you here. Despite being labelled by Felt as an endurance bike, the Z4 supports a much wider range of set-ups than is at first apparent. Much of this adjustment comes courtesy of Felt's own ingenious Variable Angle stem. This clever bit of kit has a shim that when rotated in conjunction with the stem itself, gives angle options of -16, -12, -8, 8, 12 and 16 degrees.
Add in Felt's use of a super-slim 4.5mm headset cover, which sits under the tapered spacer shown in these pictures, and it's possible to achieve a lower set-up than a Cervelo R5 with a -6 degree stem and stock 15mm headset cover. All told with headset spacers, you're looking at around 10cm of stack adjustment, so you can easily change back and forth from endurance to racing positions for each event if desired.
Frame: stiff, compact and beautifully finished
The Z4 uses the same mould as the Z2 Disc, but with slightly heavier UHC Performance grade carbon. Felt’s InsideOut moulding process means less waste inside the tubing, shedding a little weight. The BB30 bottom bracket allows a wide, stiff centre around the crankset, and ably absorbs power that’s immediately transferred to the drivetrain.
Aside from the internal cabling, there's no particular nod to aerodynamics in the tube shapes – they’re round or boxy, melding gracefully from one shape to another.
The Z4's compact, upright geometry means predictable, stable handling
Though it’s based on the non-disc Z platform, the rear brake mount is gone while the tapered fork – like the rest of the frame – is internally routed, the front disc hose threading neatly into the top, down the leg and popping out at the post-mount caliper.
It might be as subjective an observation as you can get, but the silver and black paintjob – accented with red that’s mirrored on wheels and finishing kit – looks absolutely beautiful. It sparkles without being garish and over the top. It’s just gorgeous.
Equipment: braking power and massive gear range
The SRAM Rival levers have taller hoods to accommodate the hydraulics, but remain comfortable and, if anything, they offer a more secure grip when adopting a forearms to the tops position. We’ve already mentioned the efficacious but occasionally noisy SRAM hydraulic brakes – the 160mm front, 140mm rear rotor give excellent stopping performance.
The shifting itself is spot-on in terms of accuracy, with not a single mis-shift during testing. That’s especially impressive considering the rear Rival 22 WiFli derailleur is tasked with transitioning smoothly from 11t to 32t across 11 cogs.
This massive rear block range is paired with the stiff alloy Rival crankset, which has 52x34t chainrings to give an absurdly wide ratio. The spin-happy setup is one of the bike’s greatest strengths, fitting in perfectly with the Z4’s keep-you-fresh character. There’s nothing quite as reassuring as knowing you’ve got a couple of sprockets in hand at the back should you really need them.
Thanks in part to the Rival 22 YAW front derailleur, which pivots to accommodate a diagonal chainline, the range at the back means less shifting at the front. We were happily taking on moderate rises without hitting the biggest rear cog or being forced to click into the 34t chainring. It’s almost like a 1x setup but with a get-out-of-jail-free card for when steep gradients and long climbs loom up ahead.
The downside is that there is some understandable gappiness in the cassette, with quite a pronounced shift from the churn-away smaller cogs to spin-easy larger ones. This can make finding a natural cadence on rolling roads challenging at times, but it’s a penalty that’s vastly outweighed by the overall versatility of the WiFli system if you're tackling big hills. There's also the issue of spinning out at high speeds – perfectly acceptable during sportives, but not ideal if racing.
The hydraulic Rival levers are taller then the mechanical versions and offer a better grip in some positions
The annoyance of SRAM’s gearing compared with Shimano’s remains that users of the American brand’s levers can’t brake and change gear simultaneously. This isn’t an issue in most circumstances, but just isn’t quite as practical when you want to shift gear ahead of a junction or at the bottom of a descent that leads onto a climb.
The Mavic Aksium ONE Disc wheels are stiff, roll swiftly on flatter sections of road and tackle climbs with robust efficiency. The French brand’s Aksion 25mm clinchers grip well in all conditions and serve to offer a bit of extra damping as they bulge over the brake-track free rims. At nearly 2kg without treads, tubes or rotors, they’re not the lightest out there and an upgrade in this department could make a massive improvement.
Chunky may be, but the Mavic Aksium ONE Disc wheels look great with matching red decals
Felt’s SuperLite Road VariableShape bar has a very compact 118mm drop, meaning comfort isn’t diminished when you want to get down on the drops for a change of hand positions. It’s also easy to access the levers from down there too, the upward slant of the bars putting fingers well in reach of the shifters. The SuperGel tape is grippy and exceptionally well padded while stiffness doesn’t waver even when hoiking the bars to and fro when out the saddle.
Finally, the Prologo Scratch 2 T2.0 saddle was a surprise in terms of comfort. This tester prefers a cutway but even christening the Prologo with a 60-mile sportive didn’t cause any problems at all. It’s flat, slim and with ‘just-right’ padding that’s not too hard nor soft.
Final thoughts
The Z4 is a very well-rounded bike for long days in the saddle: great braking performance; an enormous gear ratio; a good balance of stiffness and damping; that compact frame; enormous fitting range – it all adds up to a mile muncher that will help keep you fresh all day and a smile on your face. The rubbing discs are annoying at times, but that appears true of road disc set-ups generally. Lighter wheels would make it fly up climbs, but it’s not an upgrade that’s really pressing. If you want to push out mile after mile in comfort without diminishing stiffness, it could be the one for you.
Editor's note: This review was updated on 9 June 2015 to give more detail on the wide fitting options of the Variable Angle stem and headset cover, which allow the adoption of a low racing position as well as a tall, sportive-friendly set-up.