Specialized Tarmac SL8 Comp

The Specialized Tarmac SL8 Comp offers an exceptional frameset with a few spec compromises. A couple of component changes would transform the bike into a fast and comfortable machine, but at RRP, there are better ways to spend your money

There are two aspects to the first impression of the SL8 Comp. Firstly, despite the budget alloy DT Swiss wheels, this is a seriously fast bike. Whatever Specialized has done in the wind tunnel during the SL8’s development, it shows on the road.

I seemed to have a bit more speed when descending compared to a friend on his Allez Sprint with deep carbon wheels. I will be the first to admit that this is hardly scientific backing of Specialized’s aero efforts, but I was very impressed with the way the SL8 Comp found and held onto speed.

But while it is undoubtedly a fast bike, one key element of the build is letting it down.

The narrow 26mm tyres simply aren’t suitable for a modern road race bike and the fact they sit on the narrow 20mm internal width of the DT Swiss R470 rims compounds this. The result is a bike that feels harsh on anything other than good asphalt and I’d say you’re missing out on some speed too.

Given the SL8 has space for 32mm tyres, I don’t understand why Specialized isn’t making use of this. If the bike is treated to a spec change in 2026, I’d love to see this addressed.

Having been bounced around by the narrow tyres, I decided to try a set of deeper and wider carbon wheels with a set of 28mm Continental GP5000 S TR tyres.

The combination of additional tyre width, additional internal rim width and switching to a tubeless setup was instantly noticeable. The bike felt calmer, both in a straight line and in corners. I also felt faster throughout my rides and a little fresher towards the end.

Frameset

That change highlights what a peach Specialized’s 10r SL8 frame is. There is plenty of stiffness, both in the front end and through the pedals. Admittedly, I’m not the largest or most powerful rider, but having also ridden the S-Works model, I see no point in buying above the 10r frameset level.

The bike is also nice to ride on the climbs, though the 7.77kg weight for the stock 52cm bike does make the package feel a little lethargic. This is also a touch over the 7.68kg that Specialized quotes for a 56cm bike.

Heading down the freshly laid Cheddar Gorge, the SL8 Comp felt wonderfully composed and where the corners were dry, it was a fun bike on which to push the pace.

Much has been said about the Tarmac SL8 frameset in regard to its aero credentials. Specialized claims that the SL8 is 16.6 seconds faster than the SL7 over 40km, but it’s important to remember that these claims get made while a new cockpit and wheels are also being launched – neither of which you get here.

What I am pleased to see is the trickle-down of carbon tech. Specialized’s 10r carbon used to be reserved for higher end bikes, so it is nice to see the cheapest SL8 also now getting it.

But I am slightly disappointed that more thought hasn’t gone into the cockpit junction on bikes with the two-piece cockpit. With any spacers under the stem, the head tube juts awkwardly. The effect is lessened significantly when the stem is slammed, though as the alloy stem is carried forward from the Tarmac SL7, I don’t think it ever looks perfect.

But head to the back of the bike and Specialized hasn’t cut corners, giving you the same S-Works carbon seatpost which you’ll find on the Red Bull Bora pro bikes.

Wheels and tyres

The wheel and tyre package is a solid training option, but really, when compared to the SL8 Comp’s rivals, this is a disappointing compromise.

The DT Swiss R470 rims have some good features, such as brass nipples for better corrosion resistance, but their 20mm internal profile is a little narrow by modern standards and their weight feels sluggish on a bike like this.

The S-Works Turbo tyres are not awful, providing decent grip and good ride feel on newer tarmac, but in this 26mm size, they cause the bike to feel harsh on my local roads.

Groupset

Shimano’s 105 Di2 groupset is easy to love, especially with Specialized’s considered approach to the gearing choices.

Up front, you have 52/36T chainrings, while out back is a 12-speed 11-34T cassette. The combination offers plenty of climbing gears while keeping the jumps between teeth small at the faster end.

The brake setup is also good with a 160mm front rotor providing plenty of bite. I did end most rides with two honking geese, but given the super wet conditions, contamination can be forgiven.

Rounding out the groupset, the 105 Di2 levers are very comfortable in my hands. While I do miss the lever travel adjustment that you’ll find on the Ultegra and Dura-Ace levers, it’s impossible to tell which lever is in your hand while riding.

Finishing details

There isn’t much left to cover, but the Body Geometry Power Sport saddle will be a popular choice. It is a little wide for me, so I found myself perched further forward than I’d like, but given how personal this component is, I can’t mark the bike down too much.

At the front end, Specialized continues to use Supacaz’s Super Sticky Kush tape. I don’t love this tape, having found it too thin for years. It does, however, provide loads of grip for both gloved and bare hands.

Around the rest of the bike, the cover for the seatpost clamp fits nicely, as does the shroud on the back of the stem. There were also no annoying rattles during testing, suggesting the bike has been well thought out.

Geometry

On the whole, the geometry is good. The frame, in particular, is great fun to ride and you can tell that Specialized has tuned the numbers from the Venge to the SL7 and landed with what we have here.

That said, I would like to see the American brand be more progressive when it comes to things away from head angles and BB drop.

The bars on this 52cm bike, for example, are 40cm wide. I would have loved to have seen a 38, or even 36cm bar. The purpose of the bike is road racing and a narrow front end is the most effective way for a rider to improve their speed.

But look up the size chart and things get more confusing. The 54cm bike comes with a 42cm bar, which feels completely out of step with the latest bike fit trends. Save the wide bars for endurance bikes.

Similarly, the crank lengths across the size range feel a little old school. Sure, this 52cm bike comes with 170mm cranks, which is fine, but you only have to go up one size to find 172.5mm cranks.

Given that I sit on the border between the 52cm and 54cm sizes, it’s annoying to know that stepping up to the 54cm size would result in buying a load of different components.

Price and alternatives

A quick look at alternatives shows how much further you can make your money go. Giant’s £3,299 TCR Advanced 0 comes with 105 Di2, Cadex carbon wheels and wider 28mm tyres.

The bike still uses a two-piece cockpit, but Giant’s solution looks quite a bit tidier.

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Canyon, meanwhile, has the £3,299 Ultimate CF 7. Again, you’ll find Shimano 105 Di2 and while it too has alloy wheels, they are slightly wider internally and come fitted with 28mm tyres.

Key, for me, however, is the front end. Canyon’s CP0048 is an integrated carbon one-piece cockpit with cut-free height and easy width adjustment built in. I’ll admit that changing the stem length is more costly and complicated with this system, but once set up, it is very sleek.

Conclusion

The Specialized Tarmac SL8 Comp is a good bike and would be perfect for upgrading as and when you can.

The handling is fantasic and the groupset is perfect. I’d like to see some more progressive component choices being made in the future, but most are easily fixable.

If your budget is tight, I believe there are better ways to use it. If you’re simply looking to buy into the SL8 range and then upgrade, the Comp is a great starting point with a fantastic frameset that deserves better wheels and tyres.

Verdict

A good race bike that is begging for a few upgrades

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