Cervlo has unveiled the latest iteration of its spero gravel race bike, sporting a raft of evolutionary updates including a slimmer down tube and significantly dropped seatstays.Since its 2019 debut, the spero (meaning rough roads) has existed at the racier end of the wide gravel bikes spectrum, with a stripped-back frame and fork, and minimal bikepacking-friendly fixtures.Continuing that approach, the new spero features tube shapes culled from Cervlos extensive library, with plenty of the frames elements drawing inspiration from its road-going siblings most obviously the Soloist.Unlike most new bikes, Cervlo has reduced the speros frame stiffness in some areas, which it claims improves performance.Also unlike the plethora of new gravel bikes for 2024 including the Merida Silex, GT Grade, Santa Cruz Stigmata and Canyon Grail geometry has been left largely alone.The focus is instead on improved clearance for mud and chainrings, along with frame-shape tweaks designed to make the spero a more agile racer.Warren Rossiter has spent some time riding the new Cervlo spero Rival XPLR AXS and you can read his review here.Frameset evolutionIt's evolution rather than revolution for the new spero. - CerveloThe new spero frame has seen subtle changes rather than a radical redesign. It now has a lower standover height across all sizes, while both chainstays have been dropped further to improve chainring clearance.Cervlo has looked at the carbon and layup schedule, too, introducing more compliance to the frame and fork.Most noticeable is the slimmer down tube, along with seatstays that are dropped much further down the seat tube.Cervlo has decreased the head-tube stiffness to 95Nm/deg from the 110Nm/deg of the original and 112Nm/deg of the premium spero 5. However, bottom-bracket stiffness is up on the original 228Nm/deg versus 220, but less than the spero 5s ultra-stiff 240Nm/deg.Improving compliance without compromising the bike's handling was the priority. - CerveloThe goal for the new bike was to maintain the speros performance-oriented handling, but improve compliance through the saddle and bar, while retaining drivetrain efficiency.Also outgoing is Crvelos long-standing press-fit BBRight bottom bracket, in favour of a threaded BBRight T47-A. Its the same unit used on the Soloist and its not the only tech borrowed from the brands all-rounder aero road bike.Up-front, the new spero shares the ST36 system, where the hoses are semi-integrated into the frame using a D-shaped fork steerer.For bikes with mechanical drivetrains, Cervlo offers a new cable-management system called the clippy clip. Here, a split bearing cap (available in 14mm and 30mm depths) enables the cables to be channelled, along with the hoses, through the head tube.The cables and hoses dont run fully internally through the stem, making servicing and transporting the bike easier.Cervelo has stuck with the geometry formula on the new spero. - CerveloA lot of Cervlos rivals have moved closer to MTB-inspired geometry, with long front-centres, longer forks and slacker head angles.However, Cervlo has stuck to its steeper, road-oriented head angle (72 degrees on sizes 54, 56, 58 and 61cm; 71/71.5 on 48 and 51cm respectively). Its similarly steep at the rear 73 degrees (56, 58, 61cm), 73.5 (54cm), 74 (51cm) and 74.5 (48cm).The new frame offers 7.4mm of mud clearance with a 700x42c tyre, thanks to chainstays that have increased to 425mm from 420mm. The wheelbase is only a millimetre longer in a size 56cm.The fork offers the same clearance and Cervlo has kept the switchable dropout it calls the Trail Mixer.Chainstays have increased to 425mm from 420mm, while the down tube has slimmed and the seatstays have dropped further. - CerveloCervlos fork dropout insert alters the position of the fork offset fore and aft by 5mm horizontally. It claims this means the bike will feel the same running a relatively slender tyre on a 700c wheel, compared to a maxed-out 42mm gravel tyre.The forks chin has a much cleaner integration into the head tube, which is reminiscent of the Soloist. Like the original spero, the new bike retains its three bottle boss sets, down tube protector and bento box mounts on the top tube.Mud clearance on the drivetrain is also improved. With a 46-tooth chainring, theres 2.7mm clearance, 1.8mm with a 48-tooth ring and 3.2mm for a 52-tooth ring.The dropped seatstays influence a revised seat-tube shape with a much more prominent wheel cut-out. The seatpost has a standard 27.2mm diameter and is compatible with gravel dropper posts, while the rear dropout is now SRAM Universal Derailleur Hanger compliant. 485154565861 Seat tube angle (degrees)74.57473.5737373 Head tube angle (degrees)7171.572727272 Chainstay (mm)420420420420420420 Top tube (mm)512532553575591608 Head tube (mm)83107133159188214 Fork offset (mm)534946464646 Trail (mm)58.658.658.658.658.658.6 Bottom bracket drop (mm)78.578.5767673.573.5 Wheelbase (mm)99010001010102710461063 Standover (mm)690732764788814838 Stack (mm)505530555580605630 Reach (mm)370379388397406415 Edit Table 2024 Cervlo spero range detailsThe spero makes up the Experiential range with the Caledonia, Soloist and Rouvida. - CerveloThe spero is part of Cervlos Experiential range, alongside the Caledonia, Soloist and Rouvida e-road bike.Dont expect any superbike builds, as found on the S5 and R5, because the range tops out with a SRAM Rival AXS XPLR model that gets Reserve 40/44 gravel wheels, at 5,200.The UK range opens with a Shimano GRX610 2x 12-speed model, with Alexrims Boondocks wheels, at 3,100. International buyers will find both a GRX400 model for $2,400 and a mechanical Apex XPLR 1 model at $3,500.The premium spero 5, with its lighter, stiffer frameset and D-shaped seatpost, remains in the range.spero Rival XPLR AXSspero Rival XPLR AXS. - CerveloGroupset: SRAM Rival XPLR AXS, 12-speedRear wheel: Reserve 44Front wheel: Reserve 40Tyres: WTB Vulpine TCS Light 700x40cHandlebar: Cervlo AB09 CarbonStem: Cervlo ST36 AlloySaddle: Prologo Dimension STNSeatpost: Cervlo SP19 Carbon 27.2RRP: 5,200 / $5,500 / CA$7,400 / 5,799 / AU$8,000spero GRX RX820spero GRX RX820. - CerveloGroupset: Shimano GRX 820 12-speedWheels: Fulcrum Rapid Red 300Tyres: WTB Vulpine TCS Light 700x40cHandlebar: Cervlo AB09 CarbonStem: Cervlo ST36 AlloySaddle: Prologo Dimension NDR T4.0Seatpost: Cervlo SP19 Carbon 27.2RRP: 4,400 / $4,000 / CA$5,700 / 4,899 / AU$5,300spero Apex XPLR AXSspero Apex XPLR AXS. - CerveloGroupset: SRAM Apex 1Wheels: Fulcrum Rapid Red 300Tyres: WTB Vulpine TCS Light 700x40cHandlebar: Cervlo AB09 CarbonStem: Cervlo ST36 AlloySaddle: Prologo Dimension STNSeatpost: Cervlo SP19 Carbon 27.2RRP: 4,200 / $4,300 / CA$3,500 / 4,899 / AU$5,500spero APEX XPLR 1spero APEX XPLR 1. - CerveloGroupset: SRAM Apex Rear wheel: Alexrims Boondocks 7DFront wheel: Alexrims Boondocks 7DTyres: WTB Vulpine TCS Light Fast Rolling Dual DNA 60tpi 700x40cHandlebar: Zipp Service Course 70 XPLR AlloySaddle: Cervlo SaddleSeatpost: Cervlo Alloy 27.2 15mm offsetStem: Cervlo ST36 AlloyRRP: N/A / $3,500 / $4,350 / 3,599 / AU$4,400spero GRX RX610spero GRX RX610. - CerveloGroupset: Shimano GRX 610Rear wheel: Alexrims Boondocks 7DFront wheel: Alexrims Boondocks 7DTyres: WTB Vulpine TCS LightHandlebar: Zipp Service Course 70 XPLR AlloyStem: Cervlo ST36 AlloySaddle: Cervlo SaddleSeatpost: Cervlo Alloy 27.2 15mm offsetRRP: 3,100 / $3,600 / CA$4,650 / 3,699 / AU$4,500spero GRX RX610 1xspero GRX RX610 1x. - CerveloGroupset: Shimano GRX 610Rear wheel: Alexrims Boondocks 7DFront wheel: Alexrims Boondocks 7DTyres: WTB Vulpine TCS Light 700x40cHandlebar: Zipp Service Course 70 XPLR AlloyStem: Cervlo ST36 AlloySaddle: Cervlo SaddleSeatpost: Cervlo Alloy 27.2 15mm offsetRRP: 3,100 / $3,600 / CA$4,650.00 / 3,699 / AU$4,500spero GRX RX400RRP: $2,500 / CA$3,700 / 3,599spero FramesetCervelo Aspero frame. - CerveloRRP: $2,500 / CA$3,500 / 2,799