Best of Test 2023: Most comfortable gravel bike - Specialised Diverge STR Expert
Julian Schultz
· 31.12.2023
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Modesty is not exactly the ornament of the Diverge STR. On the contrary. The Specialized attracts attention, or more precisely the frame - because where the top tube and seat tube of a diamond frame are usually firmly connected, a carbon and metal construction stretches into the gap: a hydraulic shock absorber. In combination with the suspension element on the handlebars, this makes the Diverge STR the first full-suspension road bike from the Americans - and earns it the award for the most comfortable gravel bike in the 2023 TOUR test.
Purists who value the gravel bike as a robust and uncomplicated companion on gravel tracks and roads will probably question the point of a gravel full-suspension bike at this point. Complicated technology definitely makes gravel racers heavier, generally more maintenance-intensive and possibly more susceptible to defects. But does this also apply to the Diverge STR Expert?
Gravel bike with full suspension
Gravel bikes with full suspension, which almost resemble mountain bikes, are nothing new in the increasingly colourful gravel segment; prominent examples include the BMC Urs LT with suspension fork and elastomer bumpers on the rear triangle or Cannondale's Topstone Carbon Lefty. On the Diverge STR, Specialized has supplemented the familiar Future Shock suspension on the handlebars with an active hydraulic damping element on the rear triangle, which keeps the springy seatpost in check. The development department in Morgan Hill put a huge amount of effort into this, with the Americans spending around five years tinkering with the frame.
It was literally blood, sweat, tears and overtime - peppered with nagging doubts as to whether the technology would ever make it across the finish line. | Chief developer Luc Callahan on the Diverge STR
"It was literally blood, sweat, tears and overtime - peppered with nagging doubts as to whether the technology would ever make it across the finish line," head developer Luc Callahan is quoted as saying on the Specialized website. After several prototypes, the result was a frame with rear suspension, the centrepiece of which is the hydraulic damper on the top tube. The seat post itself is located in a second carbon tube, the end of which is clamped low down in the seat tube, roughly at the height of the bottle cage.
The seatpost springs backwards/downwards over its entire length, resulting in up to 30 millimetres of travel at the saddle; this travel is tamed by the shock so that the seatpost does not bob annoyingly when pedalling. The firmness of the system can be adjusted: On the shock in three stages while riding or in the workshop by turning the carbon insert. Depending on the mounting position, the carbon insert has two different degrees of hardness and is supplied in two versions.
No rocking, no creaking
Not only does this sound complicated in theory, it also takes some time in practice to understand and adjust all the setting options. Even Specialized point out that the system should "only be fitted by a professional mechanic" due to its complexity. During the ride, however, the US bike is completely convincing and irons over bumps impressively and effortlessly. The Diverge STR absorbs particularly rough impacts with the suspension at the front and rear, whereby the Future Shock System raises the handlebars relatively high and puts the rider in an emphatically upright sitting position.
If you have to take your foot off the accelerator on an unsprung gravel bike to avoid hitting potholes or roots, the Diverge in the softest setting of the damper simply skips over them. No bobbing, no creaking. The system simply works. Despite the high wheel weight of 9.7 kilograms, the Specialized with its locked suspension system is surprisingly fast, even on asphalt. The 42 millimetre wide tyres, which were fitted to our test bike without a tube, provide more than sufficient damping.
It remains to be seen which target group the bike and its sophisticated technology will appeal to - but it is likely to remain comparatively small: The Americans have put a price tag on the Diverge STR that excludes many potential buyers from the outset. The cheapest model we tested with a combined single drivetrain from SRAM Rival and GX Eagle costs €7000. At the market launch, it cost 500 euros more. For the S-Works version, Specialized is even asking 14,000 euros. Do you really want to regularly expose such a fine piece of technology to mud and dirt and the bombardment of swirling gravel?
Specialised Diverge STR Expert at a glance
- TOUR grade: 1,8
- Price: 7500 Euro >> e.g. available from Liquid Life
- Weight: 9.7 kilogrammes
Weights & geometry
- Frame/fork/steering bearing weight: 1652/452/64 grammes
- Frame sizes: 49, 52, 54, 56, 58, 61 (test size bolded)
- Seat/top/head tube: 490/570/131 millimetres
- Stack/Reach/STR: 618/388 millimetres/1.59
- Wheelbase/caster: 1045/53 millimetres
Equipment
- Drive/gear shift: SRAM Rival eTap/SRAM GX Eagle eTap (1x12; 40, 10-50 t.)
- Brakes: SRAM Rival (160/160 mm)
- Wheels/tyres (weights): Roval Terra/Specialized Tracer Pro 42 mm (f./h. 1525/2317 g)
Measured values & individual scores
- Weight of complete wheel: 9.7 kilos | Grade: 3.7
- Steering head stiffness: 112 Nm/° | Note: 1.0
- Lateral stiffness fork: 0 N/mm* | Note: 1.0
- Bottom bracket stiffness: 64 N/mm | Grade: 1.0
- Seatpost spring stiffness: 35 N/mm | Grade: 1.0
- Spring rate fork: 0 N/mm* | Note: 1.0
*The lateral stiffness of the fork cannot be determined with the TOUR test stand due to the design. In addition, the comfort measurement of the fork does not provide any indication of the actual suspension travel at the handlebars due to the design. The evaluation takes into account both the design and the measured value on the handlebars.
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