Nicolai / Geometron G1 GPI
Wheel Size: full 29’’, 29’’ front / 27.5’’ rear, and full 27.5’’ setups possible
Travel:
- Standard configuration: 162 / 175 mm rear (adjustable); 170 or 180 mm front
- ST configuration: 142 / 155 mm rear (adjustable); 140 or 150 mm front
- LT configuration: 182 / 200 mm rear (adjustable); 190 or 200 mm front
Geometry Highlights:
- Sizes offered: S, M, L, XL, XXL
- Headtube angle: 63.3° (Factory 29’’ setup; adjustable, and varies by size)
- Reach: 498 mm (Factory 29’’ setup, size Large; varies slightly based on geometry settings)
- Chainstay length: 456–463 mm (Factory 29’’ setup; adjustable)
Frame Material: Aluminum
Price (including VAT):
- Frame and Gearbox: £5,099
- Frame, Gearbox and EXT Storia V4 Shock: £5,849
- Frame & fork packages, rolling chassis, and full builds available; see Geometron’s website for details
Intro
We’ve been big fans of the Geometron concept over the years here at BLISTER, to the extent that our Bike Editor owned the G16, the prior G1, and is now testing the updated version of the G1. For those unfamiliar with what Geometron is all about, the current brand emerged from a project between Mojo Rising founder, Chris Porter, and high-end German manufacturer Nicolai as a means of testing some rather novel (especially for the time) geometry concepts. Nicolai is known for their obsessive attention to detail and fabrication quality, but the bikes that emerged from that partnership are more than just nice to look at. Though they still might qualify as extreme in some regards, they arguably ushered in the modern long-and-slack geometry that is now seemingly ubiquitous for bikes with aggressive intentions.
Nicolai has clearly never been afraid to experiment with new concepts, and they have an extensive track record of some wild-looking gearbox bikes over the past couple of decades — heck, these days they’re offering gearbox and belt drive-equipped XC/Trail bikes and Gravel bikes. As with the origins of the Geometron partnership, it appears that Nicolai may again be a part of the next chapter in mountain bike design. While gearboxes have previously been rather niche, momentum around belt drive-equipped gearbox designs has been picking up thanks to Gates’ Belted Purse initiative, which offers a €100,000 prize to the first rider to win a World Cup round on a bike equipped with a Gates belt drive.
While most of that belt drive activity has centered around downhill racing, Geometron has now jumped on board by announcing the new Geometron G1 GPI. GPI stands for Gates/Pinion, and the new bike mates a G1 chassis to a Pinion C1.12i Smart.Shift gearbox and Gates Carbon Drive belt system. That combination of Geometron geometry and adjustment range matched to a belt-driven gearbox is about as unique as it gets, so let’s wade into the details.
The Frame
While the big differentiator here is the gearbox, the frame itself is quite unique, too. As with the updated Geometron G1, the frame is made of 7020 aluminum by Nicolai in Germany. The suspension design is the familiar Horst Link layout used by Geometron’s past bikes, with a flip chip at the shock mount pumping out the same 162 mm or 175 mm of rear travel in the factory configuration. Geometron says that the kinematics deliver a 30% progression rate (we’re not sure which travel setting this refers to), but unlike cassette-equipped bikes which have variable anti-squat due to the changing chain position, the fixed rear cog of the G1 GPI provides a constant anti-squat value of 115% at 30% sag. Anti-squat is 70% at sag.
As with the standard G1, the G1 GPI retains the massive amount of adjustability afforded by Geometron’s Mutators. Located at the rearward chainstay pivot and the forward seatstay pivot, Mutators are essentially replaceable chips that allow for geometry adjustment without impacting suspension characteristics. The G1 GPI can accommodate full 29’’ setups, mixed 29’’ front and 27.5’’ rear wheel setups, or a full 27.5’’ arrangement.
As with the standard G1, different Mutator configurations can also unlock shorter or longer travel configurations by swapping in different shock sizes. So, while the stock 230 x 65 mm shock allows either 162 mm or 175 mm of travel via the flip chip in the rocker link, a 210 x 55 mm shock creates the option for 142 mm / 152 mm, and a 250 x 75 mm shock bumps things to 182 mm / 200 mm. The G1 GPI is approved for forks ranging from 150 mm to 200 mm, and it’s dual crown approved, too.
Drive System
Let’s get into the heart of the G1 GPI: the Pinion C1.12i Smart.Shift gearbox. Pinion has been one of the big players pushing the proverbial gearbox boulder up the hill, and their C1.12i Smart.Shift system is their most advanced offering.
The C1.12i system offers 12 gears, with consistent 17.7% steps between each gear and a huge 600% total range. Gearboxes are unique in that while they aren’t as accommodating of shifting under power, they can shift while coasting, without any pedal movement.
Unlike the mechanical version of Pinion’s gearboxes which use a rotary shifter (think Grip Shift), Pinion’s Smart.Shift system uses a wired but electronic paddle shifter. The real benefit of the Smart.Shift system though is that the electronics in the gearbox help to time when the gearbox shifts, ultimately aiming to work around some of the conventional limitations of gearboxes when it comes to shifting under power. While Pinion still says that the system can cancel shifts in certain situations to protect the gearbox from damage, we’re curious to see how well the electronics help bring the gearbox shifting experience closer to conventional derailleur systems when under power.
While gearboxes can use chains too, the Gates Carbon Drive belt system used with the G1 GPI is also exciting. Belt drives offer appeal in that they don’t need regular lubrication or cleaning like a chain, and they also run quietly. The end result is that the gearbox and belt combo should require virtually no regular maintenance. As a side note, because the gearbox moves the heart of the drive system to the main frame, the rear wheel drops a whole lot of weight typically associated with a cassette and derailleur. That reduction in sprung mass should yield better suspension performance, but again, we’ll have to see for ourselves.
It’s worth noting that the Smart.Shift system requires charging of a small battery pack, but the battery life is rather impressive — claimed to be about 20,000 shifts or roughly 100 operating hours. In the event that a buyer wants to go the fully mechanical route, Geometron can supply the G1 GPI with Pinion’s rotary shifter (again, think Grip Shift) and their mechanical C1.12 gearbox.
Fit & Geometry
As hinted above, the Geometron G1 GPI offers a dizzying array of configuration options thanks to the Mutator chips. We’ll focus here on what Geometron calls their Factory Setups, which is the stock configuration.
The G1 GPI varies slightly from the regular G1, but by rather tiny amounts — for example, a 2 mm difference in reach on the baseline 29’’ configuration for size Large. As we noted in our First Look for the new G1, Geometron has actually reined in the reach figures a good bit from the prior generation G1, though they’re still on the longer side for each nominal size. The size range runs from Small to XXL, so we’ll use the Large as a middle reference point.
In full 29’’ guise, the G1 GPI gets a 63.3° head tube angle mated to a 498 mm reach. Chainstay length is set at 456 mm for sizes Small through Large, which is quite lengthy, particularly on the smaller sizes, and steps up to 463 mm on sizes XL–XXL.
Another signature aspect of the Geometron design is the steep seat tube angle mated to the long reach, which goes a long way toward mitigating the effective top tube length and, therefore, the seated cockpit length. In the case of the Large, the seat tube angle measures 78.4°, paired with a long, but not crazy long, 634 mm top tube length.
Stack heights are quite tall across the board. The Large features a 658 mm stack, while the XXL towers above any other bike I’m aware of with a 688 mm stack. Buyers looking to run an existing fork (or a dual crown) should bear in mind that the long head tube lengths (140 mm on a Large) demand a whole lot of steerer tube — massive 160 and 170 mm head tubes on the XL and XXL could pose some challenges in running a dual crown fork.
There are also mixed wheel (29’’ front / 27.5’’ rear) and full 27.5’’ setups to account for, too. Different Mutators are required for those wheel size changes, so be sure to order additional Mutators from Geometron if you want to make wheel size changes at home. Each configuration varies slightly from the full 29’’ version, but not by much — the chainstay length on the Large remains the same, while the reach varies by a few millimeters (495 mm on the mixed wheel configuration, and 499 mm on the full 27.5’’ one). The stack gets even taller on the mixed wheel bike, jumping to 670 mm on a Large, while the 27.5’’ mode stays relatively consistent with the 29’’ one at 657 mm.
Geometry charts for full 29’’, mixed 29’’/27.5’’, and full 27.5’’ setups are as follows — though Geometron publishes a “Mutation Chart” on their website which shows the range of geometry adjustment available for each frame beyond these Factory Setups.
The Build
Being an extremely boutique bike, it’s perhaps unsurprising that Geometron offers several options for purchasing the G1 GPI, ranging from frame and gearbox to a single complete build option.
For starters, the frame and gearbox option costs £5,099, whereas shelling out £5,849 gets you an EXT Storia V4 specially made for the G1. Other options include adding an EXT ERA V2.1 fork (£7,224), fork and Bike Yoke Revive seatpost (£7,524), or a rolling chassis that includes Hope Fortus 30 SC wheels (£7,849).
The one complete build option is as follows, but it’s quite a nice one — retail is £9,100 including VAT:
- Drivetrain: Pinion C1.12i Smart.Shift w/ Gates Carbon Drive CDX belt and sprocket
- Brakes: Formula Cura 4 or Hope Tech 4 V4 (203 mm front / 180 mm rear rotors)
- Fork: EXT ERA V2.1 (170 mm)
- Shock: EXT Storia V4 G1 Spherical
- Wheels: Hope Fortus 30 SC
- Dropper Post: Bike Yoke Revive (185 mm or 213 mm options available)
Non-UK buyers should note that all prices include VAT.
Some Questions / Things We’re Curious About
(1) It’s unique that Geometron offers a gearbox-equipped version of the G1 that we’ve already been spending time on — so how much of a difference does the centralized mass of the gearbox design make, particularly in suspension performance?
(2) Pinion’s Smart.Shift system seems like a clever way to engineer around some of the shifting limitations of a gearbox, but how well does it work in practice, particularly while shifting under load?
(3) How much different does the belt drive configuration feel compared to the chain-driven bikes we spend so much time on otherwise, and what advantages or drawbacks does it bring?
Bottom Line (For Now)
With the G1 GPI, Geometron has adapted their proven frame design to the world of gearboxes — and with all of the buzz around gearboxes at the moment, their timing couldn’t be better. Perhaps we shouldn’t be surprised to again see the Geometron / Nicolai collaboration yielding some interesting bikes, but the G1 GPI has us rather intrigued. Watch this space, as we’ll certainly be trying to get our hands on one in the not-too-distant future.
Such a sweet rig. I’m hoping you guys can get one of these to compare to the standard drivetrain G1. I’m thinking my next bike will be a G1. The low maintenance of the gearbox combined with the sealed pivots might be an the ticket for PNW riding.
The G1 platform is definitely special, and we are as curious as you are to see how the gearbox and belt drive combo fares in our damp climate. Keep an eye on the site as we are very much hoping we can get our hands on one of these.