Geometron has bolted a Pinion C1.12i gearbox – with its 12-spur gear system and electronic Smart.Shift shifter – into its G1 gravity-focused bike, with a Gates Carbon Drive belt drive completing the package.
With a near maintenance-free drivetrain, extensive geometry adjustability, mullet-wheel setup compatibility and a focus on reliability, the Geometron G1 GPI is a bike built to last – and adapt as a rider's interests or trends move on.
While excitement over gearbox bikes has bubbled along for years, 2025 seems to be the year they've caught the zeitgeist – helped no end by the relative explosion of Pinion-equipped downhill bikes about to be raced by the likes of Atherton and Intense.
Why has Geometron added a gearbox?
Gearboxes have always been a popular wish-list item for many riders. Their low-slung position, lack of low-hanging derailleurs and sealed mechanism offer numerous advantages.
The system's weight, centred around the bottom bracket, is low and central between the wheels' contact points, which should give a bike a much more balanced feel.
It also means there's less unsprung mass at the rear wheel, because there's no cassette and derailleur. This means the rear wheel is better able to react to impacts, enabling it to track the ground more effectively.
One factor rarely mentioned, which Geometron highlights, is that building a bike around a gearbox has a positive impact on designing the suspension kinematics – specifically, how the suspension system reacts to force inputs.
Anti-squat is the force that counteracts pedal bob. Brands frequently quote this in their marketing material, but the figure depends on which gear is selected – with a typical derailleur drivetrain, the amount of anti-squat depends on the gear selected.
The Pinion system has a constant rear-sprocket and drive-sprocket size, so this figure can be controlled easily, because the designers only have to work with one physical gear ratio.
As such, Geometron's G1 GPI has a constant anti-squat of 115 per cent at 30 per cent sag.
As a brand that focuses on reliability, the reported advantages of a gearbox are also a natural fit.
Pinion quotes a service interval of 10,000km for its system, and the belt drive requires no lubrication.
At the heart of the matter
The G1 is a 162mm/175mm-travel bike built for exploiting gravity to its fullest.
The brand was among the first to push extreme geometry figures – long reach, slack head angles and steep seat angles.
The G1 is still at the forefront of geometry, even if the rest of the market has started to catch up.
Head angles sit below 64 degrees, seat angles above 78 degrees and reach ranges from 459mm to 534mm over the five sizes on offer.
Geometron extolls the adjustability on offer with the G1.
Its 'Mutators' enable quick and easy adjustments to the chainstay length, head angle and bottom bracket height. They are also used if riders want to switch rear-wheel size.
In addition, longer or shorter shocks can be used to alter travel, while 150 to 200mm-travel forks can be fitted.
Pinion's C1.12i Smart.Shift
Pinion's gearbox offers a 600 per cent gear range (the equivalent of a non-existent 10-60t cassette) across 12 gears, with consistent 17.7 per cent steps between gear ratios.
The internals ensure that power is delivered via two pairs of gears in every selected gear.
The gears can also be shifted while the cranks are stationary – something Charlie Hatton expressed to BikeRadar was great on a DH race course, because gears can be shifted mid-air, ready for quickly changing track pitches, meaning every pedal stroke is made in the right gear.
The Smart.Shift system is an electronic shifter for the Pinion gearbox. This includes Pinion's Start.Select tech, which automatically puts the gearbox in an appropriate gear for setting off. Pre.Select can be used to enable automatic cadence-dependant shifting when coasting.
Geometron G1 GPI prices and specs
You can buy the frame and gearbox for £5,099, or add in an EXT Storia shock, bringing the package to £5,849.
Adding an EXT ERA fork takes the package to £7,224, while selecting a BikeYoke Revive dropper post brings it to £7,524.
A rolling chassis, which includes Hope Fortus 30 wheels, brings it all up to £7,849.
Geometron offers a full custom-build programme, too.
