Priority Bicycles hangs its hat on belt-driven, non-traditional drivetrains. In fact, there isn’t a metal chain or external derailleur on any bike in the brand’s extensive lineup. 

From kids’ bikes to electric commuters, every Priority bicycle uses a low-maintenance Gates Carbon Drive belt. The drivetrain systems vary from single-speeds and internally geared hubs to gearboxes like the new Pinion Smart.Shift.  

Gearboxes are having a moment in the mountain bike world, but haven’t seen much use or acceptance in the gravel market — the Priority Gemini Smart.Shift aims to change that. This is one of the first widely available drop-bar gravel bikes featuring Pinion’s latest Smart.Shift gearbox system.

I’ve been testing the Priority Gemini Smart.Shift Gravel ($3,499) bike for the past 4 months on the gravel roads and trails near Reno, Nev. From smooth singletrack to pristine high-desert gravel and plenty of miles on gritty pavement, I’ve put this bike through its paces.

In short: The Priority Gemini Smart.Shift is a unique entry to the gravel bike market. It has a Gates Carbon Drive belt and a Pinion Smart.Shift gearbox. While this drivetrain has some notable advantages, it takes getting used to and has one primary drawback. Otherwise, the Gemini’s geometry, ride quality, and weight lend themselves well to all-day comfort and far-flung adventures.

Looking for a new gravel bike? Check out our guide to the Best Gravel Bikes.

Priority Gemini Smart.Shift Review

I’ll spend most of this review discussing the performance of the gearbox drivetrain. While that is arguably the most compelling aspect of the Gemini, there’s more to this bike than the gearbox. I’ll start with a rundown of the bike and its performance before moving on to the Pinion Smart.Shift system.

Priority Gemini Smart.Shift Details

Priority sells the Gemini with the 6061 aluminum frame I tested or a titanium frame. The complete build with the aluminum frame costs $3,499. Upgrading to titanium costs an additional $2,000 and gives you a 1-pound weight reduction. Regardless of frame material, both options come with a carbon fork. 

Priority designed the frame to house the Pinion Smart.Shift. The Pinion gearbox is housed at the bottom bracket, in the downtube. Otherwise, the frame looks fairly standard, with a traditional shape and design. The frame has internal cable routing, including ports to add a dropper post. 

The front triangle has mounts for two water bottles, plus one on the underside of the down tube. There’s also a set of three-pack mounts on the top tube, front and rear fender mounts, and rack mounts. Curiously, given the Gemini’s adventure and bikepacking focus, there aren’t three-pack mounts on the fork.

Priority sells the Gemini in four frame sizes, small to extra large, and claims these fit riders between roughly 5’2” and 6’4”. The bike has a total weight capacity (rider, gear, and cargo) of 275 pounds. My size XL test bike weighed 26 pounds, set up tubeless and without pedals.

Geometry

Priority defines the Gemini as the “lowest maintenance gravel bike available for adventure riders, tourers, and recreational gravel riders.” As such, the relatively neutral geometry caters to user groups and riders interested in all-day comfort. You’ll want to look elsewhere if you’re looking for a racy or aggressive ride. 

The head tube angle, seat tube angle, and chainstay length are at or around the norms for modern gravel bikes. Its moderate length reach — 400 mm on the XL frame I tested — and high stack contribute the most to the more casual and upright body position. Riders can also tinker with stem spacers or stem length to dial in the fit as needed.

Components

The Priority Gemini Smart.Shift’s retail price is $3,499 — no small potatoes. The bulk of that cost goes toward the Pinion gearbox and associated components. The rest of the build won’t exactly turn any heads, but it is functional and fairly well suited to the bike’s intentions.

The Gemini rolls on a set of 700c WTB KOM i23 wheels with a matched set of 40mm-wide WTB Vulpine gravel tires. The tires and the wheels can be set up tubeless; however, the wheels came with just a standard rim strip installed. Converting these wheels/tires to tubeless required installing tubeless rim tape and valve stems.

The cockpit has a size-specific alloy drop handlebar — 440 mm wide on the XL — with a gravel-oriented 12-degree flare. Priority wraps this bar with a comfortable and grippy Microtex tape and clamps it to a 90mm alloy stem (my XL test bike has a 100mm stem). Out back, a comfy WTB Volt saddle sits atop a carbon fiber seatpost.

A set of TRP Hywire hydraulic disc brakes with 160mm rotors front and rear handles braking duties. As of now, the TRP Hywire is the only drop-bar-specific brake/shifter that pairs with the Pinion Smart Shift electric shifting system.

Priority Gemini Smart.Shift Gravel Bike: The Ride

Before I get into the weeds about gearboxes, let’s discuss how the Gemini rides. Well, it rides exactly how you’d expect a 26-pound gravel bike with a relaxed geometry would. I found it easy to get along with, surprisingly smooth, and generally well-suited to its recreational, touring, and adventurous riding intentions.

The neutral and comfort-oriented geometry put me in a fairly upright riding position. The shorter reach was most noticeable, so I stretched that out a bit by lowering the stem under the spacer stack. Otherwise, the touchpoints worked well for me. The WTB Volt saddle, TRP brake hoods, flared handlebars, and bar tape were comfortable.

With its beefy aluminum frame, I assumed the Gemini would feel a bit harsh. On the contrary, one of the first things that stood out to me was its forgiveness over chunky gravel and chatter. I took it down some seriously rough gravel roads, and it surprised me with its supple and compliant ride feel. Some of that can probably be attributed to the WTB wheels. They’re perfectly adequate, but they aren’t the stiffest wheels around. 

At 26 pounds, the Gemini is heavier than most gravel bikes on the market. A fair portion of that weight is in the gearbox, which weighs more than most traditional drivetrain setups. Fortunately, that weight is centered and low, and I didn’t notice it from a handling standpoint. However, the weight was noticeable in the flats and on climbs compared to lighter and zippier bikes. 

The WTB Vulpine tires worked great on surfaces ranging from pavement to loose, dry gravel. The versatile tread rolled surprisingly quickly on the tarmac and gripped predictably on dirt and gravel surfaces.

The 40mm width was reasonable for mixed terrain rides, with time split between pavement and gravel. But they felt narrow for pure gravel riding, especially in loose conditions. With clearance for up to 50 mm tires, there’s plenty of room to go bigger.

I’ve never used TRP brakes on a drop-bar bike, but they performed surprisingly well. The lever feel was great, and the brakes were plenty powerful. 

Pinion Smart.Shift

Gearboxes aren’t new, but they’ve steadily gained traction in various cycling segments. While more traditional chain-driven derailleur setups are the dominant drivetrain, there is a vocal minority of gearbox advocates. Weight distribution, low maintenance, reduced risk of damage — gearboxes have some notable advantages.

Until recently, the available mechanically actuated gearbox systems weren’t practical for a drop-bar bike. Pinion’s latest electric Smart Shift gearbox and the TRP Hywire brake/shifter levers have provided a solution. TRP designed these for the Pinion gearbox, making it possible to shift it from the levers, like traditional drivetrains.

Pinion bases the Smart.Shift gearboxes on its C line of gearboxes. The Gemini uses the 12-speed C1.12i. Pinion builds 18-speed, nine-speed, and six-speed Smart.Shift gearboxes for other applications. As the name suggests, the gearbox houses all shifting components, which function more like an automotive transmission. The sealed magnesium housing keeps dirt and moisture out of the system.

Unlike a more traditional derailleur drivetrain, the gearbox sits around the cranks. The crank spindle passes through the gearbox and directly drives the gears. The spur gearing uses two sub-units that mate together to create varying gear ratios. In this case, a four-gear and a three-gear unit pair make the 12 separate gears.  

The C1.12i gearbox provides a massive 600% gear spread across its 12 speeds. That range is much wider than SRAM Transmission’s 520% and Shimano’s 510%. Additionally, cyclists can shift gears while coasting or stopped, and Pinion even claims that the Smart.Shift system shifts well under load — more on that later. Instead of a chain, a Gates Carbon Drive belt connects a sprocket on the cranks and a sprocket on the rear wheel. 

The Smart.Shift system is electric and runs off a battery that occasionally needs charging. Pinion says the battery can last up to 20,000 shifts (approximately 100 hours) before recharging. Pinion also has an app to get firmware updates, calibrate your shifting, customize shift buttons, and more.

So why choose a gearbox over a derailleur drivetrain? Low maintenance is one of the main reasons. The Gates Carbon Drive belt lasts for a claimed 30,000 km (18,000 miles). It never needs to be lubed and rarely, if ever, needs to be cleaned. The gearbox itself has a 6,000-mile service interval before the oil needs to be changed. Additionally, there is no derailleur to break or knock out of alignment.

For these reasons, a gearbox drivetrain could be an excellent option for riding super long distances, overnight touring, or bikepacking adventures. It could also be great for anyone who simply loathes bike maintenance.

Riding With Pinion Smart.Shift

So what’s it like riding a gravel bike with a gearbox? It was a bit of a mixed bag, if I’m being honest. In some ways, it was fantastic, but in others, it fell short of my expectations.

While I think that gearboxes are generally pretty cool and the technology is advancing rapidly, I’m not sure it’s the right choice for me. That said, I see the appeal and how a gearbox gravel bike could be a good fit for specific riders and types of riding.

The Bad

I’ll start with what I disliked about riding with the Pinion gearbox. Despite Pinion’s claim that the Smart.Shift gearbox shifts well under load, I felt it had some serious limitations. Downshifting under heavy load was problematic. I’ve read that it works much better than the previous non-electric systems, but I’ve never tried them, so I can’t compare them directly. 

The main problem was that the times I needed to shift most, grinding uphill while climbing, there was too much load in the system. When the system was overloaded, it would cancel shifts. Unlike a derailleur drivetrain, which will shift even when you probably shouldn’t, the gearbox would simply refuse.

The inability to downshift at critical moments meant I was often stuck in too hard a gear while climbing. Or I had to back way off the power and dump a bunch of momentum to get into a lower gear. Neither of those was ideal when I was working my hardest up a steep incline.

To be fair, sometimes the system would shift under power. Shifting into higher/harder gears was consistently more successful. Downshifting, however, required perfect timing of the shift and the lowest torque in my pedal stroke. Downshifting with any power going into the pedals required an adapted shifting technique. 

Of course, there are limits to shifting any drivetrain under load, but I found the limit was much lower with the Smart-Shift system. Essentially, I needed to relearn how and when to shift to time it perfectly with cadence and load. Otherwise, I would hear the noise of my shift being canceled again.

Did I adapt to it over time? Yes, somewhat, but … I never got to a point where it wasn’t still frustrating. I needed to reset my expectations and had a hard time doing that. 

Another thing I didn’t love was the TRP Hywire shifters. The hoods were comfortable, and the brakes worked well, but I struggled with the shifters. The shifter paddles are small, very close together, and quite sensitive, leading to many instances of accidental shifts or hitting the wrong button at an inopportune time. 

The Smart.Shift charging dongle also stuck out in an awkward spot by the head tube and would occasionally rub on my knee while pedaling. The charger was also comically large, so it would be awkward to bring with you on bike tours. Surely this could be improved.

The Good

I’ll finish with what I liked about riding with the Pinion gearbox. First, it was always super quiet and stayed that way over hundreds of miles of testing. This was remarkable since the belt never needed to be lubed or cleaned, and I never had to make any adjustments. 

I also enjoyed the ability to shift without turning the cranks while coasting downhill and while stopped. When I was at a stoplight, I could drop a couple of gears so that I wasn’t awkwardly starting from a stop in too high of a gear. 

One of the big claims about Smart.Shift system is lightning-fast shifting. I can confirm that the actuation speed was impressive. With a light tap of the shifter, you can hear the little motor in the gearbox go to work almost instantly. In that regard, it worked very well.

Additionally, the Smart.Shift system’s battery life was fantastic at 100 hours or 20,000 shifts between charges. Sure, you need to charge it occasionally, but 100 hours is easily several weeks of riding for most people. Plus, the 6,000-mile service interval should keep most riders out of the shop for a very long time. That’s a year or two, depending on how much you ride.

Priority Gemini Smart.Shift: Who’s It For?

If you’ve been wishing for a gearbox on a drop-bar gravel bike, consider your wish granted — the Pinion Smart.Shift gearboxes and TRP Hywire drop-bar shifters have finally made it possible to combine the two. There are some other boutique options, but the Priority Gemini is one of the most accessible in terms of price and availability.

It’s not light or racy, but the Priority Gemini Smart.Shift is exactly what Priority intended it to be. While the gearbox may be its most notable feature, the Gemini’s forgiving ride and agreeable geometry are well-suited to its touring, bikepacking, and recreational riding intentions. Add the super-low-maintenance gearbox to the mix, and this could be the perfect bike for long-distance rides and adventurous bike tours. 

While the new Smart.Shift gearbox may work better than its predecessors, but it still takes some time to get used to it. Riders must adapt somewhat to account for the shifting performance under load. Assuming you’re willing to do that, then this might be the low-maintenance adventure bike of your dreams.