Specialized S-Works Tarmac SL8 - SRAM Red eTap AXS

The Specialized S-Works Tarmac SL8 claims to be lighter, faster, stiffer and more comfortable than the SL7, a bike that was already world-class. Two months with the range-topping SRAM Red eTap AXS model certainly didn't fail to impress – the competition once again has some catching up to do!

If you read our launch story and first ride review of the SL8, you'll already know the new Tarmac is very similar to the bike it replaces, the Tarmac SL7. The geometry is all but identical, the looks are very similar, and it's still designed to be the 'one bike to rule them all.'

The key changes over the SL7 are that the frame is 120g lighter, the complete bike seen here has a new cockpit, there's a claimed 6% improvement in rear compliance, it's allegedly a few Watts faster at race speed, and it's yet stiffer.

Like the SL7, the latest Tarmac comes in S-Works, Pro and Expert models. The top-of-the-range S-Works frame benefits from the most advanced carbon layup, and hence the lowest weight (more on that in a minute).

The S-Works frame is available either with Shimano Dura-Ace or the SRAM Red AXS build that we have here. These have claimed weights of 6.6kg and 6.8kg respectively, and both will set you back a cool £12,000. That might sound like a kick in the teeth, but it's actually less than the current top-of-the-range SL7 or Aethos. You can also go for just the S-Works SL8 frameset, which will set you back £4,750.

Weight

We weighed our size 56cm review bike at 6.94kg, which makes it one of the lightest to grace our scales in recent years. It's a little heavier than the 6.8kg claimed weight but, given that our review bike had an out-in-front computer mount and one of the heavier colour schemes (around 40/50g over the lightest), it seems reasonable.

For me the frame weight of just 680g is the most impressive SL8 statistic, and given that it's 120g (or 15%) lighter than the already very competitive SL7, it's better than nearly all of us predicted – or thought possible.

At 680 grams it's 90g lighter than the LAB71 Cannondale SuperSix Evo 4, and 50g lighter than the Factor 02 VAM which claims to be the 'world's fastest climbing bike'.

Given the accompanying stiffness, compliance and aero claims, the frame weight is quite the feat of engineering. But as with all superlight bikes, I am left questioning the real-world impact. Specialized's own figures suggest that you'd be just 20 seconds quicker over the Tourmalet; a worthwhile advantage if you're a World Tour pro, but less important if you're an amateur who rarely finds themselves beasting the world's most brutal climbs.

I'd personally look to save myself the best part of two grand and take a 100g hit with the non-S-Works frame. It is, after all, still lighter than the SL7 and just 10g heavier than the LAB71 SuperSix.

In conclusion, then, the low weight is extremely impressive, but certainly not the reason I'd consider buying this bike.

Speed

Without a wind tunnel, it's impossible to validate Specialized's claims that the new SL8 is 16.6 seconds quicker over 40km, but it doesn't seem unrealistic given the new aero headtube shaping and the integrated bar/stem. The 16.6-second saving amounts to around eight Watts at 45kph, with around half coming from the bar/stem and half from the frame itself.

Specialized has an almost unfair advantage when it comes to aero research, as it's got both a supercomputer for CFD (computational fluid dynamics) simulations and a wind tunnel for testing prototypes and final bikes.

Out on the road, the SL8 feels every bit the race bike, and is up there with the fastest on my regular testing loop.

Geometry

Despite supposedly being a new bike from the ground up, the S-Works SL8 is clearly more evolution than a revolution. In my opinion, that's no bad thing.

The SL7 is a bike I got on with really well, as I found in our comparison of the SL7, the Pinarello Dogma F, the Cervelo S5 and the Colnago V4Rs. The Specialized's geometry, for one thing, really works for me.

Just like the SL7, the SL8 has a race-proven geometry, so as you'd expect it's pretty aggressive with a long and low position. This 56cm frame has a 73.5-degree head and seat tube angle, with stack and reach measurements of 565mm and 395mm respectively. This gives quick steering that's more than capable of nailing a twisty criterium race, yet enough stability for those wild top speeds down an Alpine pass.

Note that this is a thoroughbred race bike designed for flexible riders who're well used to spending time in low, heavily-tucked positions. Even compared to other race bikes the SL8 is on the aggressive side: for example, the Colnago V4RS is hardly a shopping bike and yet has a 7mm taller head tube, a 10mm greater stack height, and a one degree slacker front end.

When using the bike for its intended purpose it feels very balanced and, thanks to the handling being very precise, you can carry a lot of speed into the corners. Sometimes very light, stiff bikes can feel a little 'flighty' over rough road surfaces at high speed, but the Tarmac never really does.

Ride feel continued...

And that brings us to compliance, because this is another area that the SL8 claims to have improved. In the saddle, you might not initially notice the 6% improvement in rear compliance, but after three hours or so in the saddle, you'll likely be thankful for it.

You might be thinking, 'But this is a race bike, why do I need it to be comfortable?' Well, the answer is of course speed. The Specialized engineers explained to me that the additional compliance is in direct response to the pro team's feedback; they want to ride grand tours on 26mm tyres without getting beaten up.

You might think this change would be right up my annoyingly bumpy street. However, it's a tricky one to test when the change is so small.

On its stock setup (26mm RapidAir tyres and butyl tubes) the SL8 offers roughly the same comfort as the SL7 on 28mm Vittoria Corsa G2.0s with latex tubes. I did a few back-to-back long rides switching the wheels and tyres between bikes, and will say that with both frames on the same wheels and tyres, the difference is noticeable – albeit subtle.

However, riding both bikes on both sets of tyres showed that you shouldn't expect to find this new 6% change as noticeable as you would find a tyre or tube upgrade.

Stiffness

I'll be the first to admit that I never had a problem with the stiffness of the SL7. It was more than capable of coping with my sprints, which are by no means pro-level at around 1,200 Watts.

However, to my surprise, the most noticeable improvement here the extra stiffness around the bottom bracket, as it makes other bikes feel plain dull. Out of the saddle this bike feels electric; obviously the low weight only helps with this addictive feeling, but it's that stiffness which really makes the bike.

With so much material removed from this area I can't even begin to guess how Specialized has done it, and to be honest I don't really care. The result is a bike which wants to be thrashed up hills; it made me want to sprint against my mates at the tops of climbs, and it made me feel that all my pain and graft were being turned into forward motion.

The one word I'd use to describe the bike as a whole is 'direct' – a surprise to me, really, given it has such a compliant rear end.

Finishing kit and components

As previously mentioned, this S-Works model sits at the top of the tree in terms of frame tech and components. And wearing a SRAM Red eTap AXS drivetrain, Roval Rapide CLX II wheels and a Roval Rapide cockpit, there's nothing short of top tier.

Red eTap AXS has been around for some time now, but remains a high-quality, performance-orientated groupset. I won't delve too deep into the pros and cons of the 12-speed wireless system here, as we've gone into eTap in depth already, but what I will say is that the gearing is actually a sound choice.

A 10-33T cassette on the back and a 48/35 chainset up front might sound small for an out-and-out race bike like this, but we're not all pros; for the majority of riders and terrain, it's great. The 12-speed range is very impressive and will easily cover you for everything from laid-back endurance rides to hard race efforts, while the biggest gear offers a taller ratio than a 52Tx11T could on a 2x11-speed.

Of course, if you require more gears in either direction then SRAM caters for that with a multitude of chainring sizes and a wider-range cassette.

Although I'm a big fan of SRAM Red it's worth noting that the Dura-Ace Di2 model costs the same; is also 12-speed; results in a bike that is 200g lighter (more bragging rights at the cafe); and is unlikely to be superseded as quickly given that it was only released last year.

Whichever you choose though a power meter is included in the price, as you should rightly expect from a bike costing this much.

Wheels

The Roval Rapide CLX II wheels are 51mm and 60mm deep front and rear respectively, and tubeless-ready too – although they ship with butyl inner tubes. If I were to purchase an SL8 the tubes would be the first thing to go: in my opinion, they have no place on a £12k superbike.

The wheels are excellent and have repeatedly been shown (by us and others) to be some of the fastest in the world. I've also been impressed with the stability from by the super-wide front wheel. If you're a weight weenie or climber then you may want to look at alternatives, but the majority – from weekend warriors to World Tour sprinters – will be very happy with the weight, aerodynamic performance and behaviour of the Rovals.

The seatpost is proprietary and available in 0mm and 15mm setbacks. Although it looks very similar to that on the SL7 and Allez Sprint, it is in fact a few millimetres narrower for improved aerodynamics. The downside is it's no longer large enough to house a Di2 battery, though that now clips onto the bottom (a neat solution).

The handlebar is also from Roval, and whereas the Expert and Pro models get a conventional bar and stem, the S-Works gets a new integrated cockpit.

The benefits are lower weight, improved stiffness and (according to Specialized) a roughly 4W drag saving at 45kph. The main drawback of a system like this is obviously the lack of adjustability, though, so make sure you've got the right one fitted before walking out the shop!

The tyres are also top end: S-Works Turbo RapidAir 2Bliss Ready. It'd be better if they arrived set up 2Bliss Already, but then I would personally consider switching from 26mm widths to 28mm anyway. The rear-end compliance does a good job of taming the abysmal UK roads as-is, but going a little wider brings even more comfort at the expense of very little. Wider rubber also helps protect that very wide front rim from potential stone strikes.

Other components of note are the Supercaz bar tape (which performs well and has been a regular on S-Works bikes for some time now), and an S-Works Power carbon saddle. Again, that's a classy bit of kit.

So the finishing kit is top tier and there's no skimping on componentry whatsoever. This is as good as it gets when buying a bike off the shelf!

Value

How does this £12,000 bike stack up against the competition? Luckily, we've already reviewed quite a lot of this year's peloton-ready machines, so let's see.

The Colnago V4RS is a natural competitor but, with an RRP £999 higher, it's hard to overlook the fact it's also heavier and doesn't feel as nimble.

The Pinarello Dogma F Super Record EPS is also more expensive at £12,400, though I had the pleasure of riding that one too and it was indeed superb. Although the complete build is a very similar weight to the SL8, that's largely thanks to the very light Campagnolo Hyperon wheels, and they're unlikely to be as aero as the Rovals given their much shallower depth. It's also worth noting that you don't get a power meter with the Pinarello.

There are World Tour bikes that can compete with the SL8 on value, though: the Scott Foil RC Pro doesn't include a power meter either, but is a fair bit cheaper to start with at £10,499. Once again it is heavier, mind you.

At £12,000 this is way beyond the reach of all but the wealthy few, but nevertheless the S-Works SL8 is more worthy of this price tag than most. The sensible(ish) money would undoubtedly be spent on something further down the range, but if you're after the pinnacle of bike technology, the SL8 has to be high up the list.

If you're not, then the SL8 Pro is the one I'd go for. The frame is only marginally heavier and claims to have the same performance in every other regard, you still get Roval Rapide wheels with the same rims (albeit different hubs), and the SRAM Force or Ultegra R8170 groupset options are both excellent. And at £8,000 it's fully £4,000 cheaper.

Overall

I keep coming back to the Tarmac SL7 and for good reason: it's still one of the best road race bikes in the world. The SL8 is quite simply better, albeit marginally, in just about every way.

It's undeniably lighter, it's undeniably fast and the simultaneous improvements in stiffness and compliance – which may well sound like familiar marketing waffle – are small but undeniably there. They have real-world benefits to the ride feel, and edge the Tarmac closer to race bike perfection. This is surely the bike to beat in 2024, and to my mind it's the best race bike in the world right now. Your move, everyone else!

Verdict

Narrowing in on perfection - this is the new race bike benchmark