The 2023 Specialized Diverge STR gravel bike adds a unique rear Future Shock seat tube with a hydraulic top tube motion damper to control the flex. Combined with their steer tube Future Shock up front, the bike keeps the rider floating over chatter for a smoother, faster ride.
The design is wild, leveraging almost the entire length of the seat tube (not seat post, but seat tube) to provide flex, giving it a lot of travel. Here’s everything you need to know about the new Diverge…
What’s new? What’s the same?
The Specialized Diverge STR will sit at the top of their gravel bike lineup alongside the Crux S-Works, just with a very different rider in mind. The Crux will remain their lightest, race-focused bike, but the Diverge STR will likely be the bike of choice for their pros on rougher courses.
The standard Diverge design, without the rear Future Shock, will remain in the lineup, too. In fact, the new STR model shares the almost the same geometry, with a few subtle tweaks:
- Stack & Reach are identical
- STR BB drop is 85mm, 5mm more than standard
- Chainstay length is 429mm, 4mm longer than standard
- Seat tube angle is 0.5º steeper, but…
…the slightly steeper seat angle is offset once you sit on it and the system is sagged, making the effective seat angle the same as the standard Diverge once your weight is on it. Specialized suggests sliding your saddle 5-10mm more forward to account for the sagged flex, putting you in the same position as on a fully rigid bike.
Tire clearance is 700×47 (or 650Bx2.1″), and downtube SWAT storage comes standard with included tool bags (fill it with whatever you want, or stuff a rain jacket in there).
How much does the Diverge STR weigh?
An S-Works Diverge STR frame weight is just 1,100g (claimed, FACT 11R frame, size 56, painted with no hardware, and without damper…keep reading), about 100g more than a standard S-Works Diverge frame.
And it’s a “rigid” frame, which was the point. Specialized wanted to maximize power transfer and overall efficiency, so the bike handles like a normal rigid bike. Stand up and the rear Future Shock does nothing, turning your arms and legs into the suspension. Thankfully the front Future Shock still delivers its 20mm of travel, standing or sitting.
All in with the full rear Future Shock system, an STR frame will weigh almost 400g more than a standard frame, but that includes the headset, SWAT system, and hardware.
A complete 56cm S-Works Diverge STR weights 8.5kg (18.75lb) setup tubeless, out of the box. A Pro model weighs 8.9kg (19.6lb), and an Expert model weighs 9.5kg (20.9lb).
How does the Diverge STR rear Future Shock work?
To be clear, this is not a “full suspension” bike in the traditional sense. The goal is to suspend the rider so they can remain seated, comfortably, and power through chunky courses without wasting energy hovering over the saddle or bouncing around.
Specialized has been working on how to do this since at least 2017. Recent versions of the Roubaix and standard Diverge dropped the seatpost clamp lower to give the seatpost more room to flex. That was fine for endurance road bikes, where you may race on cobbles occasionally. But gravel bikes were taking on ever more challenging terrain.
Clockwise from top left in the image above are prototypes starting with an eccentric bottom bracket that allowed an inner shaft to move inline with the seat tube. From there, they moved to a vertically suspended seatpost with a rear air shock connected to the bottom bracket, keeping effective saddle height unchanged even as the rider “felt some suspension.
Both of those early designs worked-ish, but would be far too complicated to manufacture at scale. Eventually, they moved to the extended flexible seatpost concept, which was simpler and provided the desired benefits while maximizing stiffness and minimizing weight.
The rear Future Shock provides up to 30mm of travel by using what is effectively a really long seat post anchored very low in the frame that’s unattached to the top tube or seat stays.
There are, actually, two seat tubes on the frame. The external one you see, and a separate internal carbon-and-glass fiber tube that bolts into the frame just above the bottom bracket. That attachment point acts as the pivot, allowing the entire tube, and the seatpost inserted into it, to act like a leaf spring.
The external seat tube is ovalized near its top, creating room for the internal tube to flex rearward.
Specialized will offer 9 different seat tubes, and each of those has two distinct flex characteristics thanks to different layups and material combinations, providing 18 total “tunes” to work for almost any rider weight.
Each bike will come with two tubes covering the expected range of rider weights for that frame size, in total covering riders from 110lbs to 275lbs. (The bike has a total rider+cargo weight limit of 275lbs)
Here’s the catch: A really long carbon leaf spring could flex a lot, and then rebound quite forcefully, bucking the rider. So it needed to be controlled, and that’s where the hydraulic damper comes in.
Essentially the same as the damping circuit found in a suspension fork or shock, the STR damper has separate compression and rebound circuits.
The compression (which, in this case handles the extension of the “shock”) has a three position adjustment – open, medium, and firm. This controls the motion, preventing it from catapulting you forward on every rebound, and eliminating any “bobbing” that could occur from an undamped system.
The rebound is adjustable with a hex wrench through a port under the top tube, making the system fully adjustable.
How do I adjust the Future Shock seat tube suspension?
Each internal post has two effective layups, with a clocking groove that keeps it aligned. Simply rotate it 90º to switch the stiffness. The posts are clearly marked with numbers.
The higher the number, the stiffer the post, and it’s a linear progression. Meaning, a post marked “60” is twice as stiff as a post marked “30”. Or, a 30 post will flex twice as much as a 60 post.
The numbers indicate their flex as measured in N/mm, which, honestly, means nothing in terms of which post you should choose…but, you know, fun fact?
Specialized says the two posts included with each bike should make most riders happy, giving them four distinct options. They also say most riders can tell a noticeable difference with a 10% change (ex. going from a 40 to a 44 post), and that a 20% change is very noticeable. Combine those with the three compression damping settings and it makes it easy to fine tune for anyone’s preference.
The damper connects to the post with an alloy “tendon”, and it has a wrench faces to hold it level when unbolting it so that you don’t bend and damage it when swapping posts.
But you only need to loosen it to swap internal posts; your actual seatpost can be adjusted and removed like normal. And it uses a normal 27.2 seatpost, so you can use any post you like, even switching to an alloy post if you want to reduce overall flex.
What about frame bags, racks & fenders?
The fork has three mounts, letting you run accessory cages or a lowrider rack, and fender mounts. The rear, though, has no mounts for either rack or fender.
Top tube bag mounts come standard, and strap-on frame bags can be used as long as they don’t interfere with the damper or rub the rubber boot around the seat tube. Saddle packs and bags can be used like normal, but if it’s heavy you may want to use a stiffer post.
2023 Specialized Diverge STR prices & options
All models use a threaded bottom bracket, flat mount brakes and thru axles with full internal routing…for brake hoses and wires, it’s designed only for electronic shifting groups. You’ll notice only SRAM builds here, however you should still be able to build a bike with Shimano Di2 since the inner seat tube is hollow and would allow the battery wires to pass through to the seatpost battery.
An S-Works frameset ($6,000), including fork with Future Shock steerer is available if you’d like to do just that. A small wire entry port sits under the rear brake hose entry at the head tube, and there’s an exit port just above the rear dropout.
As for dropper seatposts, there are no mechanical routing options, but you could install a Reverb AXS post. The frame is 1x only, so you won’t be giving up front derailleur compatibility to add the wireless dropper.
All bikes get Supacaz Super Sticky Kush handlebar tape, which is awesome.
2023 Specialized S-Works Diverge STR
The S-Works model gets the top of the line FACT 11R carbon frameset. MSRP is $14,000 (€15,000 / £13,000). Spec highlights include:
- SRAM Red eTap AXS shifters, Quarq power-meter crankset, brakes
- SRAM Eagle XX1 derailleur, 10-50 cassette, chain
- Roval Terra CLX wheels w/ Roval LFD hub & ceramic bearings
- Roval Terra carbon handlebar
- Tracer Pro 700×42 tires
- Body Geometry S-Works Power carbon saddle
- S-Works carbon seatpost
- Satin Forest Green/Dark Moss fade
It’s worth noting that this is the first complete bike that’ll ship with the 3D-printed S-Works Power saddle, and that these Roval Terra CLX wheels are new, too.
They combine the already light Terra rims with the lighter LFD hubs from the Alpinist CLX II road wheels, which uses a DT 180 Ratchet EXP 36T internal (10º engagement) and SINC ceramic bearings. They’re light, but will have their own official launch with all the tech details in the near future.
2023 Specialized Diverge STR Pro
The Diverge STR Pro comes in a bright Satin Blaze/Violet Ghost Pearl color and retails for $9,500 (€9,500 / £9,000). Spec highlights are:
- SRAM Force eTap AXS shifters, crankset, brakes
- SRAM Eagle X01 derailleur, 10-50 cassette, chain
- Roval Terra CL wheels w/ DT350 hub
- Roval Terra carbon handlebar
- Tracer Pro 700×42 tires
- Body Geometry Power Pro saddle with ti rails
- S-Works carbon seatpost
2023 Specialized Diverge STR Expert
The Diverge STR Expert downgrades to standard FACT carbon and retails for $7,500 (€7,500 / £7,500). Spec highlights are:
- SRAM Rival eTap AXS crankset, shifters & brakes
- SRAM GX Eagle AXS derailleur, cassette & chain
- Roval Terra C wheels w/ new DT 370 Star Ratchet hub
- Specialized Adventure Gear Hover alloy handlebar
- S-Works carbon seatpost
- Tracer Pro 700×42 tires
- Body Geometry Power Expert saddle with ti rails
The Diverge STR Expert comes in two colors – Satin Black/Diamond Dust, and Satin Harvest Gold/Gold Ghost.
Framesets are only available in the US and Australia ($8,500 AUD), and Australia only gets the Expert complete bike ($10,500 AUD).
Stay tuned, we’ve been riding one and will post the review soon…
