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Gravel Gear

The Specialized Diverge STR debuts Rear Future Shock, an innovative approach to gravel suspension

The suspension system comes with only a modest weight penalty while maintaining the responsiveness of a rigid frame.

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Back in 2016, Specialized introduced Future Shock, a road-bike suspension system located at the stem and headtube that introduces 20mm of travel to the bike.

It was born on the Roubaix endurance race bike for the namesake cobbled race in northern France and has trickled its way into a variety of Specialized bikes since, including the Diverge gravel bike.

Now the Diverge is the launching point for a brand new suspension system called Rear Future Shock. Debuting on the new Diverge STR, Rear Future Shock is an innovative approach to gravel suspension and one that comes without a substantial weight penalty or other drawbacks that accompany traditional suspension systems.

The future of Future Shock is here. You just have to look back a little bit to find it. 

Also read: Review: Specialized S-Works Diverge STR and its Rear Future Shock suspension

The S-Works Diverge STR

How Rear Future Shock works

It’s a little confusing to understand, especially if you don’t have the bike right in front of you, but the Diverge STR has taken the idea of suspending the rider in place as the bike moves below — the inspiration for Front Future Shock — and applied it to the rear of the bike.

All it takes is a cursory glance at the Diverge STR to notice that something doesn’t look quite normal around the seatpost-top tube-seat stay junction. 

All it takes is a cursory glance at the Diverge STR to notice that something doesn’t look quite normal around the seatpost-top tube-seat stay junction. (Photo: William Tracy)

The seat stays connect to the top tube, that much is normal, but well ahead of the seatpost. The post sits far back and appears to be attached by a thin piece of metal across a gap.

What’s going on is that Specialized has taken a concept present to an extent in the previous Diverge and Roubaix road race bikes (and many other bikes like the Canyon Endurace) and put it on steroids. All those bikes feature a compliant, flexible seatpost with the ability to travel 20mm fore and aft (though in practice it is much less than 20mm of travel), absorbing bumps and road chatter. 

The Diverge STR and its Rear Future Shock gets an even more compliant seatpost in this area through a component called a Framepost that slots into the seat tube how a seatpost normally would. Essentially, the Framepost is a buffer between the seat tube and seatpost and acts as a spring that lets the seatpost and rider more liberally move back and forth to the tune of 30mm. And unlike the seatpost of the previous Diverge, you’re getting to experience most of that full 30mm of travel, not just a little bit of that theoretical 20mm of travel a heavier rider experiences for a moment on a big bump with compliant seatpost designs.

But all that energy in the Framepost when a rider moves backward has to go somewhere, and where it is going to go is forward. Essentially, Specialized has created a catapult. That’s where that metal piece connecting the seatpost (well, actually the Framepost) to the top tube comes into play.

Specialized has to control the catapult for this to work. So inside the top tube is a hydraulic damper whose job it is to control how quickly the Framepost, and therefore the rider, is able to move back and forth, and it’s connected to the Framepost by that thin metal piece, called a Tendon. 

In this clear acrylic model you can see the damper inside the Diverge. The damper is also adjustable via a hex key as shown here. (Photo: William Tracy)

The damper provides bottomless travel and is controllable through a compression adjustment lever that, while not letting you lock out the system, lets you remove some compliance from the ride when you hit smoother tarmac sections. It’s similar to how the Front Future Shock 2.0 at the stem is adjustable so you can adapt the ride to differing terrain. 

See that little lever just above where the Tendon enters the top tube? That controls the damper.

The nice part is that this is adaptable to all kinds of riders. Any rider in the 110-to-275-pound range can benefit from this system due to Specialized offering many different Frameposts.

Remember, that’s the component that acts as a spring in this system. Specialized has created nine of them of differing compliance levels so riders can find one that works for them. And each Framepost has two orientations, a soft and firm side, so there are really 18 options total here. Luckily Specialized has determined typical rider weight ranges for each frame size and ships two posts that meet the majority of riders’ needs, but if those two do not work for you, there will more than likely be another that does.

The parts that make Rear Future Shock work. Any 27.2mm seatpost is compatible, but you need the Framepost (center) as well as the Tendon (right, top) for it all to work. (Photo: William Tracy)

Any 27.2mm seatpost can work in the Diverge STR, even dropper posts, and Specialized recommends against compliant ones as found on the Roubaix because the bike offers plenty of compliance.

Front Future Shock advantages

Why this system over say a suspension fork? There are a few benefits, namely weight and its ability to maintain a rigid main triangle. 

Weight

At 1,100 grams, the Diverge STR frame itself is only about 100 grams heavier than before. And in total the delta between the previous generation Diverge and the new one, when factoring in all the components, is about a pound.

And the bike itself does not feel heavy, as many gravel bikes with suspension forks do. Some of those are pushing 25 pounds. In a size 56, the S-Works Diverge STR weighs a claimed 8.5kg set up tubeless. The Pro and Expert models, also featuring Rear Future Shock, come in at 8.9kg and 9.5kg.

Rigid frame when you need it

The next benefit is ride quality. A traditional suspension fork zaps energy when a rider gets out of the saddle or otherwise puts in a big effort. The location and nature of the Rear Future Shock means that it only engages when a rider is seated, so when climbing out of the saddle, or going for the sprint win at Unbound Gravel, it performs just like the previous Diverge — or any other non-suspension gravel or road bike. 

Specialized isn’t introducing the rear Future Shock as a one-off gimmick. The brand believes in this technology so much so that it is making it the only option for an S-Works Diverge. In other words, Specialized believes the best version of a Diverge has the rear Future Shock. 

Conceivably, just as with the Front Future Shock, the rear version could make its way into more of the Specialized lineup. 

Does it work?

Specialized says so (who would have guessed?) and has done some testing to prove it. The brand claims the Diverge STR reduces vibration at the saddle by more than 20 percent compared to the previous Diverge. The tests were run with 10 different riders at 32kph using 42c tires at 35 psi. 

Head over to the VeloNews S-Works Diverge STR review to find out our experience. 

Same features that made the Diverge great to begin with

The Diverge was already a good bike, so Specialized hasn’t messed with other characteristics and features that made it successful in the first place. 

Front Future Shock isn’t going anywhere. (Photo: William Tracy)

Front Future Shock of course has stuck around, and it’s still adjustable just as before. For comfort and the capability to tackle gnarly terrain, it has the same 47c tire clearance as well. And on the down tube there is SWAT storage inside the bike accessed beneath the water bottle cage. 

SWAT storage is still in the Diverge STR.

The frame remains made of FACT 11R carbon, and despite the addition of the rear Future Shock, the frame doesn’t take on too much of a weight penalty, tipping the scales at a claimed 1,100 grams for a painted size 56. That’s only 100 grams over the previous S-Works Diverge frame. 

Geometry Chart

Stack and reach are the same between the previous Diverge and the new Diverge STR. Specialized has made only a few tweaks between the two, all with the intent of creating the exact same fit while incorporating the Rear Future Shock.

The BB drop has increased from 80mm to 85mm, as has the chainstay length from 425mm to 429mm. And because the Rear Future Shock sags ever so slightly when a rider sits down, Specialized has made the seat tube angle about 0.5 degrees steeper to compensate, resulting in a similar fit.

Pricing

The Diverge STR continues the march toward ever higher price points in road and gravel bikes, costing $14,000 for the most expensive S-Works build, a $1,500 premium over the previous S-Works level Diverge.

The Pro model, shown here in “Satin Blaze,” costs $9,500.
  • S-Works: $14,000
  • Pro: $9,500
  • Expert: $7,500
  • Frameset: $6,000