Specialized has finally unveiled the new Tarmac SL8 on the day of the men’s road race at the 2023 World Championships in Glasgow, Scotland.
The new bike features an elongated head tube, called the ‘Speed Sniffer’, among a host of other tweaks aimed at making the Tarmac SL8 the fastest road bike it has ever produced.
Nevertheless, the geometry remains unchanged compared to the Tarmac SL7.
An S-Works Tarmac SL8 Fact 12r carbon frame is claimed to weigh 685g in a size 56cm, while the second-tier Fact 10r carbon frames are said to weigh 780g.
The new bike will cost as much as £12,000/$14,000/€14,000/AU$19,900 for the S-Works model, while the second-tier Tarmac SL8 Pro is priced at £8,000/$8,500/€8,500/AU$11,900. The Tarmac SL8 Expert costs £6,000/$6,500/€6,500/AU$9,400.
We took the new Tarmac SL8 out for a test ride on the morning of the 2023 World Championship men’s road race in Glasgow. You can read our initial findings in our Specialized Tarmac SL8 review.
Starting with aero…
The previous-generation Tarmac SL7 arguably set the trend for modern race bike design, with many brands adopting its all-in-one approach.
The new SL8 marks an evolution of that design, with an aerodynamic overhaul to the bike’s “leading edges”, which Specialized says makes it “16.6 seconds faster over the fastest aero bike we’ve ever made [the Venge]” at 45kph.
This comes firstly via the new pronounced head tube, which the brand says presents a sharper, more efficient profile to the wind.
In order to achieve a deeper head tube, Specialized says it’s commonplace for brands to pull the trailing edge back, effectively filling in the gap.
However, wanting to preserve the same geometry and handling characteristics of the SL7 at the behest of riders such as Remco Evenepoel, Demi Vollering and Kasper Asgreen, Specialized’s forward-extending design is said to improve aero performance while keeping the steerer in the same place relative to the previous bike.
The head tube is topped with the new Roval Rapide integrated cockpit, which is said to save 4 watts compared to the old two-piece setup used on the SL7. There are 15 options, with bars ranging from 38-44cm wide and 75-135mm stem lengths.
While the integrated setup is said to be the most efficient, Specialized says the head tube spacers also work neatly with the old two-piece SL7 cockpit (which will be found on some builds), while the bike can be run with any stem fitting a 1-1/8in steerer.
Further back, the seat tube has been narrowed to the same width as the SL7’s seatpost, with the new seatpost naturally slimmer again to fit inside.
This is said to help the “fast moving, dirty” air in this area to pass more efficiently than the previous design, although Specialized doesn’t specify by how much.
The Aethos influence
Specialized has also addressed the Tarmac SL8 frame’s weight, stiffness and compliance in a bid to improve the bike’s overall speed on varying terrain, using the Aethos (the brand’s lightweight road bike) as a starting point.
Instead of shooting for deeper aero-profiled sections all over the bike, Specialized's road product manager, Miles Hubbard, says the non-leading edge areas of the bike – the down tube, seat tube, seatpost and seatstays – are all purposefully designed to improve the bike’s speed “in the real world”.
The tube profiles are marginally rounder than the Tarmac SL7, which the brand says makes them lighter and enables them to bear the load of the rider and the forces produced more efficiently.
On the one hand, an S-Works frame is set to be the lightest widely used frame in the professional peloton, weighing a claimed 685g in a size 56cm.
Meanwhile, the Fact 10r carbon-framed Tarmac SL8 frames are said to weigh 780g.
Along with the weight loss (an S-Works Tarmac SL7 frame weighed a claimed 800g), Hubbard says that the Aethos-inspired tube shapes are influential in improving compliance through the saddle by 6 per cent compared to the SL7.
To cap off the headline claims, Specialized says the bottom bracket, head tube and fork have been stiffened, delivering a net 33 per cent gain in stiffness-to-weight ratio.
All-in, Specialized says its simulations indicate a pro rider would finish Milan-San Remo 2 minutes, 8 seconds faster than if they were aboard a Tarmac SL7, and would save 20 seconds for a complete ascent and descent of the Tourmalet mountain pass.
Front-Loading Development
Specialized says the Tarmac SL8 was produced using what it calls a “Front-Loading Development” process.
Essentially, this involves a cyclical iterative development process, with Specialized’s engineers going back and forth between virtual carbon modelling, CFD (computational fluid dynamics) and FEA (Finite Element Analysis) to iterate the design.
None of these technologies are new, but Specialized says its use of these tools helps its engineers to remove uncertainty from the development process.
In turn, the brand says, its prototypes can be physically tested and achieve figures far closer to the numbers its software says they should, helping it to make more definitive steps forward.
Applied to the Tarmac SL8, Specialized says it started with its Fact 12r carbon material, its Aethos-developed method for lightweight carbon layup, and the new aero-optimised SL8 frame shape. It then iterated until it landed on the figures (it says) the SL8 delivers.
The brand says the S-Works Tarmac SL8 represents the 55th iteration it trialled, which it claims would have equated to around 5,000 physical prototype samples.
If it ain’t broke, don’t fix it
Following requests from the likes of Evenepoel, Vollering and Asgreen, Specialized has stuck almost completely to the same geometry as the Tarmac SL7.
Only the stack has changed, raised by 10mm as a byproduct of the interaction between the Rapide cockpit and head tube.
Like the SL7, tyre clearance remains at 32mm, while the bike continues to use a BSA threaded bottom bracket.
Specialized Tarmac SL8 availability, prices and specifications
The new Specialized Tarmac SL8 is available in five specifications. Two come with an S-Works Fact 12r frameset, while three have the Fact 10r layup.
An S-Works Tarmac SL8, built with either Shimano Dura-Ace Di2 R9200 or SRAM Red AXS costs £12,000/$14,000/€14,000/AU$19,900. The Tarmac SL8 Pro (Shimano Ultegra Di2 R8100 or SRAM Force AXS) costs £8,000/$8,500/€8,500/AU$11,900, while the Tarmac SL8 Expert (SRAM Rival AXS) is £6,000/$6,500/€6,500/AU$9,400.
Framesets are also available for £4,750/$5,500/€5,500/AU$8,900 and £3,000/$3,500/€4,000/AU$5,600, respectively.
Specialized says it encourages dealers to offer free choice of Roval Rapide cockpit at point of purchase, but the specification of 15mm-setback seatpost is fixed (albeit a zero-setback model is available aftermarket).
Meanwhile, Specialized is also set to continue selling the Tarmac SL7 frame in a Fact 9r carbon configuration, with prices and full specifications to be confirmed.
Specialized S-Works Tarmac SL8 Dura-Ace Di2
- Price: £12,000/$14,000/€14,000/AU$19,900
- Frame: S-Works Tarmac SL8, Fact 12r carbon
- Fork: S-Works Tarmac SL8, Fact 12r carbon
- Groupset: Shimano Dura-Ace Di2 R9200
- Power meter: Yes (4iiii)
- Wheels: Roval Rapide CLX II
- Seatpost: Specialized Tarmac SL8, carbon
Specialized S-Works Tarmac SL8 Red AXS
- Price: £12,000/$14,000/€14,000/AU$19,900
- Frame: S-Works Tarmac SL8, Fact 12r carbon
- Fork: S-Works Tarmac SL8, Fact 12r carbon
- Groupset: SRAM Red AXS
- Power meter: Yes
- Wheels: Roval Rapide CLX II
- Seatpost: Specialized Tarmac SL8, carbon
Specialized Tarmac SL8 Pro Ultegra Di2
- Price: £8,000/$8,500/€8,500/AU$11,900
- Frame: S-Works Tarmac SL8, Fact 10r carbon
- Fork: S-Works Tarmac SL8, Fact 10r carbon
- Groupset: Shimano Ultegra Di2 R8100
- Power meter: Yes (4iiii)
- Wheels: Roval Rapide CL II
- Seatpost: Specialized Tarmac SL8, carbon
Specialized Tarmac SL8 Pro Force AXS
- Price: £8,000/$8,500/€8,500/AU$11,900
- Frame: S-Works Tarmac SL8, Fact 10r carbon
- Fork: S-Works Tarmac SL8, Fact 10r carbon
- Groupset: SRAM Force AXS
- Power meter: Yes
- Wheels: Roval Rapide CL II
- Seatpost: Specialized Tarmac SL8, carbon
Specialized Tarmac SL8 Expert Rival AXS
- Price: £6,000/$6,500/€6,500/AU$9,400
- Frame: S-Works Tarmac SL8, Fact 10r carbon
- Fork: S-Works Tarmac SL8, Fact 10r carbon
- Groupset: SRAM Rival AXS
- Power meter: Yes
- Wheels: Roval C38
- Seatpost: Specialized Tarmac SL8, carbon
