Here’s why I won’t be upgrading to the Specialized Tarmac SL8

For over two years now, my go-to road race bike has been the Specialized Tarmac SL7. For the last fortnight though, I’ve been riding its natural successor, the S-Works Tarmac SL8. Has this new road bike impressed me enough to upgrade, or will I be sticking to the SL7 for the foreseeable? You know the answer already, but in this article and video I’ll explain why that is… 

If you read our launch story and first ride review of the SL8, then you’ll already know that the new Tarmac is in many ways very similar to the bike it replaces. For example, the geometry is the same, the looks are very similar, and it’s still designed to be “one bike to rule them all”, in Specialized’s words. 

The key changes compared to the SL7 are that the frame is 120g lighter, the complete bike has a new cockpit, there is a claimed 6% improvement in rear compliance, it’s supposed to be a few watts faster at race speed and there’s yet more stiffness. Time for some digging into whether it’s worth upgrading, and some back-to-back riding of the two bikes…

How much would it cost to ‘upgrade’?

Before we go any further, it’s worth noting that neither of these bikes are going to be winning a value-for-money award any time soon. You can go out and get yourself 95% of the performance – which is mostly down to your legs and head anyway – for less than half the price. However, the Specialized S-Works models do arguably represent the pinnacle of road bike technology available to buy right now, and that’s always going to be expensive.

The SL8, despite costing a massive £12,000 in this S-Works guise, surprised many people who had predicted it would set you back a fair chunk more. In fact, the flagship S-Works SL8 that we’ve been riding is actually £1,000 cheaper at RRP than either the S-Works Aethos or the SL7. Anyone who is angry about the £12,000 price tag should be far more angry about the price of those.

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Being a few years old, the SL7 obviously isn’t still selling at the RRP price, so right now a top-tier SL7 will set you back around £2,000 less than the equivalent SL8. Realistically that’s about the amount of money that I or anyone else looking to upgrade from an SL7 is going to have to stump up.

Does the SL8 actually ride any better?

According to Specialized, this new bike is better in every way. Let’s break that claim down and get comparing.

Speed (quicker, but not noticeably…)

First up, speed. To me this is one of the most important factors in a race bike, and if it isn’t your priority then I’d seriously consider checking out something less aggressive like an endurance bike. 

I’ve been riding the SL8 for about three weeks now, on a variety of local routes that I have benchmarked on the SL7 over the years in a variety of weather conditions. Specialized claims that the new SL8 is 16.6 seconds quicker over 40kph; but on my familiar routes, admittedly it hasn’t made me quicker by any measurable amount. I think that’s only to be expected. 

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If the claims are true, then you’d expect to save around 8 watts at 45kph. Most people’s riding won’t average that or will only reach those speeds when drafting in a group. In both cases though, you can expect to experience less than the claimed 8-watt advantage.

In the real world, you can expect to find far bigger gains from changing your position, clothing and other variables. If you have already honed your on-bike position and equipment then yes, I’m fairly confident in saying that thanks to the thinner seatpost/seat tube and tidier integrated bar, the SL8 probably does offer a very marginal speed benefit.

Geometry: the same winning recipe

In many ways, despite supposedly being a new design from the ground-up, the SL8 is an evolutionary progression rather than a revolution. In my opinion, that’s no bad thing.

The SL7 is a bike I got on with really well, something that is discussed in our comparison between the SL7, the Pinarello Dogma F, Cervelo S5 and Colnago V4Rs. One of the reasons for this is that the geometry really works for me.

In the saddle it feels very similar, because the geometry is exactly the same. This puts you in the same position over the pedals.

There are a few differences in seatposts, whereas the SL7 comes with a 20mm setback as standard, with an optional zero-degree setback option. This one comes with a zero-degree setback seatpost or a 15mm version like we’ve got fitted.

Stiffness: the biggest difference?

Although I never thought the SL7 was in any way ‘floppy’, if Specialized had have asked me what I was hoping for from the SL8 prior to its launch, increased stiffness probably wouldn’t have featured.

Even so, one of the headline claims when the SL8 launched was a huge 33% increase in the stiffness-to-weight ratio, with a particular focus on the bottom bracket area. I’ve read enough press releases to know that you can’t believe all the marketing talk, and so I wasn’t necessarily expecting to feel a difference.

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Surprisingly, switching between the two bikes back-to-back I found this was the most noticeable difference. The SL8 feels more taut at the rear end in a way that is very difficult to put into words.

This is most noticeable when climbing out of the saddle. If there’s such a thing as a ‘direct’ rear-end of a bike, then this is it.

Weight: impressive… but pointless?

To me, the most impressive stat regarding the SL8 is that the frame weighs just 680g. That’s 120g (or 15%) lighter than the already very competitive frame weight of the SL7. It’s also quite a feat of engineering considering the accompanying stiffness, compliance and aero claims.

Despite this figure blowing just about every other frame weight out of the water, I do question its importance to most riders in the real world. Yes, the bike builds up to a very competitive 6.95kg (Size 56cm in the White Fog colourway, with pedals and a bottle cage) but my SL7 is also under 7kg (albeit with lighter components on the latter). 

With like-for-like components, the SL8 is undoubtedly lighter; but for me, that 120g pales into insignificance when diluted across a full build.

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Specialized claims that the lower weight of the SL8 will offer you a meaningful advantage on any gradient over about 5%. I think the graph is a little bit optimistic, compared to software such as bikecalculator.com anyway.

Specialized’s figures suggest that you’d be 20 seconds quicker over the Tourmalet, but on climbs less than an hour long that’s obviously going to decrease. Then, there’s the fact that some pretty heavy bikes do climb surprisingly well. I usually put that down to stiffness, especially in the bottom bracket area. This leads me to think that you can’t put the SL8’s impressive climbing performance purely down to its low weight.

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If the World Tour riders can teach us anything, then it’s that weight isn’t – and shouldn’t – be the be-all and end-all. We went around the pro bikes at the Dauphine and many were in the region of 7.6kg. Not because they can’t be lighter, but rather because bike weight on most stages is a secondary concern. 

In conclusion, then, the low weight is more useful as a party piece at the cafe than on the majority of rides.

Compliance

The final thing that you’ve probably heard Specialized shouting about is the 6% improvement in rear compliance.

The roads around me are pretty bumpy, so you’d think that this was right up my street. However, it’s a tricky one to judge, because in the real world a tyre change has a far bigger effect.

For example, the SL8 with the 26mm RapidAir tyres and butyl inner tubes that it ships with offers roughly the same comfort as the 28mm Vittoria Corsa G2.0 and latex inner tube setup that I’m running on the SL7.

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Of course, I’ve been swapping over the wheels plenty enough to get a feel for both bikes on both setups, and yes, the SL8 is indeed more comfortable at the rear on rides over three hours or so.

Is this enough to make me want to switch? Let’s summarise!

Tarmac SL7 vs Tarmac SL8: worth the upgrade?

So, will I be upgrading? Nope, probably not.

Although I think that the SL8 has improved on the already impressive platform of the SL7 in just about every way, for me, the changes aren’t quite big enough to justify upgrading.

However, I will consider buying one of the Roval Rapide integrated cockpits that come on the S-Works SL8. It’s that which is responsible for over 50% of the wattage savings, and is also 50g lighter than the non-integrated affair on my SL7.

One reason that a lot of people might choose to upgrade is because of that improved rear-end compliance, and I have heard plenty of comments regarding the SL7’s unforgiving rear end. Specialized says the main motivation for this additional compliance was so that its pro teams could continue saving a few watts on 26mm tyres without getting beaten up over six-hour stages day after day.

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Personally, I don’t ride my bike that far very often. On less-than-perfect road surfaces, I’m more than happy to continue running a 28mm tyre and latex inner tube on my SL7, and forgo those few watts that I could potentially be losing.

However, say I owned neither bike. If I could afford it, which one would I buy then? It would have to be the SL8. Undeniably it’s marginally better in just about every way than the SL7, as you’d hope for with those extra three years of development. 

Let us know your thoughts in the comment section below, and keep an eye out on our YouTube channel for the upcoming video comparing the S-Works SL8 to the Cannondale Supersix Lab71.