2025 Nicolai / Geometron G1
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, XL
- Headtube angle: ~63° (adjustable, and varies by size)
- Reach: 500 mm (size Large, varies slightly based on geometry settings)
- Chainstay length: 446 to 480 mm (adjustable)
Frame Material: Aluminum
Price (including 20% VAT):
- Frame w/ EXT Storia V4: £3,600
- Frame & fork packages, rolling chassis, and full builds available; see Geometron’s website for details
Intro
Mountain bike geometry underwent a massive, massive change in the last decade or so, and Geometron arguably did more than anyone else to bring those changes about.
Their original production bike, the G16, seemed unfathomably radical when it first launched back in 2015. Its main geometry numbers — 502 mm reach (on a size Medium), 62.5° headtube angle, 443 mm chainstays, and 77° seat tube angle — still sound thoroughly modern. Sure, the stack was short (608 mm on that same Medium frame) and it rolled on 27.5’’ wheels, but the G16 was, in many ways, the first truly modern Enduro bike.
I owned a G16 long before I ever worked for Blister, and when some of the ways in which it was dated (8.5’’ x 2.5’’ rear shock, 27.5’’ wheels) started to make it less suitable as a parts-testing platform, I moved on to its replacement, the G1, as my personal Enduro bike.
The G1 brought some geometry tweaks, more modern standards in terms of part fitment, more adjustability, and a bunch of other refinements — but still bore a strong resemblance to the G16 in a lot of ways. And while there are a lot of bikes with geometry that’s a lot more similar to that of the G1 than there were when it first launched, it still felt pretty out there in terms of being notably long, slack, and aggressive.
But now there’s a new G1, and the folks at Geometron (and Nicolai, who still build the G1) have found a lot to change — maybe a surprising amount, given the declining pace of geometry evolution in the mountain bike world. Let’s see what they’ve come up with.
The Frame
The overall silhouette of the G1 frame hasn’t changed a ton, but a lot of the details have. It’s still made in Germany from 7020 aluminum and the Horst-link suspension layout with a horizontally mounted shock carries over, but they’ve tweaked a lot of the construction details.
The most visually obvious changes are the new top tube-to-downtube gusset and integrated seatpost clamp / seat tube-to-top tube gusset, both of which look very similar to those used on the Nicolai Nucleon 16. The chainstay protection has been beefed up, the headtube is now a straight 56 mm affair to make more room for offset headsets, and there’s even more geometry adjustability on offer. The top tube has a more complex profile than the old round one, and so on.
As with the outgoing G1, the new version uses “mutators” at both the seatstay / rocker link junction and the chainstay pivot to offer a massive amount of adjustability, covering geometry, wheel sizes, and now shock size / rear suspension travel as well.
The seatstay mutators are essentially spacers that bolt between the end of the seatstay itself and the pivot housing at the end of the stay, effectively varying its length and thus tweaking the G1’s geometry and / or compensating for different wheel sizes and / or rear shock lengths. (I know, it’s a lot.)
The chainstay mutators accomplish a similar goal but do so by replacing the dropout pivot housing with different clamshell pieces of varying lengths. Swapping in a longer chainstay mutator primarily lengthens the chainstays, but also lowers the bottom bracket and slackens the headtube angle a touch; going to a longer seatstay mutator primarily steepens the headtube angle and raises the bottom bracket, but also shortens the chainstays very slightly.
By varying the two mutators in conjunction with each other, the G1 has a ton of adjustability to tweak the geometry and compensate for different size wheels (to the point that it can be run with dual 29’’ ones, a mixed wheel setup, or two 27.5’’ wheels). And then a flip chip at the rear shock mount toggles between two different travel settings, with the higher position producing 162 mm of rear wheel travel, and the lower one bumping up to 175 mm and adding a bit more progression in the process.
That’s all more or less the same as the original G1, but the new version also offers two different lengths for the base chainstay and seatstay parts themselves, which extend the range of chainstay length adjustments far beyond what the original G1 offered — up to a colossal 480 mm when pairing the longer chainstay and seatstay with the longest chainstay mutators. All that geometry adjustability unlocks… even more adjustability, in the form of suspension travel options.
The 162 / 175 mm travel options referenced earlier are in the default configuration for the G1, with a 230 x 65 mm rear shock, which is meant to be paired with a 170 or 180 mm travel fork. But by mixing and matching mutator settings, you can run the G1 with a 210 x 55 mm shock to get 142 or 155 mm of rear travel (paired with a 140 or 150 mm travel fork) or a 250 x 75 mm one, for 182 / 200 mm of rear wheel travel, which Geometron recommends pairing with a 190 or 200 mm travel fork. The G1 is rated for forks up to a 605 mm axle to crown length (roughly in line with a 200mm-travel dual crown) but it is worth noting that the super long headtube on some of the larger size frames might make dual-crown fork fitment a challenge.
The rest of the frame details are focused on durability and ease of service. The brake hose and shifter housing are routed externally, with bolt-on clamps; the bottom bracket shell is threaded and features ISCG-05 tabs; replaceable inserts are used for threaded frame fittings wherever possible; and the pivot hardware all features secondary sealing to keep the elements out and grease in.
The G1 also now features a UDH for SRAM Transmission compatibility. The chainstay protection has also been beefed up and features a pass-through for the derailleur housing. The new rear triangle can be retrofitted to the original G1 front end for owners of the original bike who want to take advantage of the UDH and / or longer chainstay options.
Geometron doesn’t go into a ton of detail about the suspension kinematics of the new G1, but it doesn’t sound like they’ve changed a whole lot from the old one. The total progression is stated at 31% (in which travel setting isn’t clear) and anti-squat and anti-rise are listed at 100% and 62% at the sag point, respectively. The leverage curves for the various configurations are published in their tech sheets (see below); the other kinematic data isn’t published, but Geometron says it’s generally quite similar to the outgoing bike.
Fit & Geometry
The new G1 is offered in the same five sizes (Small, Medium, Large, XL, and XXL) as the outgoing one, but unlike most recent bike updates in recent years, they haven’t gotten longer and slacker — in fact, quite the opposite.
Reach now starts at 455 mm on the Small and grows by roughly ~20 mm between each frame size, up to 535 mm on the XXL. That’s about 15 to 20 mm shorter in a given size than the outgoing G1 (but still quite long overall); the headtube has steepened a touch, from 62.5° to around 63° in the default configuration, though it now varies by frame size, with the smaller sizes getting a slightly slacker headtube (62.6° on the Small, up through 63.8° on the XXL). Seat tube angles start at 77.8° on the Small frame and get fractionally steeper with each step up in frame size, to 78.8° on the XXL.
But while the reach has gotten shorter across the board, the stack height has grown — by a lot. The Small frame’s stack now starts at 628 mm — a number between the Medium and Large on the outgoing G1 — up to a colossal 685 mm on the XXL, with stops at 646 mm, 657 mm, and 678 mm along the way. That’s way, way taller than the outgoing bike — and pretty damn tall in general. I’ll now take my victory lap for predicting that we’d see reach and headtube angles stop getting more radical, with the new frontier for more gravity-oriented bikes being taller stacks and longer chainstays just a few weeks ago on Bikes & Big Ideas. (I promise I hadn’t seen the new G1 yet when I said that.)
And speaking of chainstay lengths: any frame size can be configured with any of the possible chainstay lengths, but the Small through Large frames default to the shorter base chainstay / seatstay assembly, which in turn can be configured to have 446 mm chainstays (default on the Small frame), 454 mm ones (Medium default), 460 mm (Large default), or 466 mm ones via mutators. The longer chainstay assembly can go as short as 460 mm, with options for 468 mm, 474 mm (XL default), or 480 mm (XXL default) and come as standard on the XL and XXL frames, but you can swap things around at the time of ordering if you’d like.
Size-specific chainstay lengths have become commonplace, but the new G1 gets a lot more size-specific geometry, from the headtube angle to the bottom bracket height, and more. Interestingly, the bottom bracket drop varies by size, in a decidedly non-linear manner. The Small frame — which defaults to a mixed-wheel configuration — gets a stated 23 mm BB drop, though it’s not clear if that’s relative to the front axle, the rear one, or the line between them (dear bike industry: please pick a standard way to state BB drop on mixed-wheel bikes and stick with it). The rest of the size range defaults to a full 29’’ setup, but, again, all frame sizes can be configured to your liking there; the bottom bracket drop on the Medium frame starts at 28 mm, with the bottom bracket lowering fractionally on the Large (30 mm drop) and XL (31 mm drop) before coming back up a little (29 mm drop) on the XXL.
Again, those numbers are all in the default configuration for the G1, with the 203 x 65 mm rear shock, a 170mm-travel fork, and the standard options for mutator settings; you can change a whole lot from there if you’re so inclined. The full spreadsheet with all the options for the standard 230 x 65 mm shock configuration is here; if you’re curious about the other configurations, the short travel tech sheet is here, and the long travel one here.
The Builds
The G1 frame comes standard with an EXT Storia V4 shock, again with spherical eyelet bearings as featured on the Storia V3 from the original G1. Geometron has a custom build configurator that lets you spec out a full or partial build of your choosing. The frame kit includes a Hope headset and retails for £3,600 (including 20% VAT); you can add an EXT Era V2.1 fork for a total package price of £4,975 (again with VAT), or keep adding parts from there.
Some Questions / Things We’re Curious About
(1) How different (or not) does the new G1 feel compared to the outgoing one? We’d imagine that the geometry changes — especially the stack height — feel substantially different, but we will need to get on one to find out.
(2) What about the sizing of the new G1? The reach has gotten quite a bit shorter, but with much, much higher stack heights across the board, will the new bike actually feel smaller, fit-wise?
(3) And what about the short- and long-travel configurations? Does the G1 still feel coherent as more of a mid-travel Trail bike, or something approaching a true DH bike, at least in terms of suspension travel and geometry numbers?
Bottom Line (For Now)
Updating what was already (and still, five years after its launch) one of the most progressive bikes on the market geometry-wise might sound like a daunting task, or a case for a very light makeover. But the new Geometron G1 looks to have evolved a lot more than we might have expected it to. We’re very keen to get on the new G1 to see how it stacks up to the old one (and the rest of market), and are working to make that happen.
Flash Review: Our Initial On-Trail Impressions
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Flash Review — Nicolai/Geometron G1
Update 12.18.2024: We’ve spent a lot more time on the new Geometron G1 and have experimented with a lot more of its myriad customization options. Check out what we’ve learned so far.
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Although the nominal reach might have gotten shorter, the taller stack creates a longer reach, when you actually set your handlebar to a certain height.
Essentially you are measuring the reach higher up on the steerer. More stack adds about 0.4 X that amount to the reach at a certain a height. So, 50mm more stack equates to about 20mm more reach at a given stem height.
(I know David knows this, but it’s not really called out in the text)
As a 6’5”/196cm tall rider, I’d love to try one of those XXL’s. I might finally find a bike that is too big for me!
I really love what they are doing here. If only they routed the cable and hoses through the headset, it would be perfect ;-0
@tjaard I’m 6’6” and rode an XXL G1 for a while, but ended up sizing down to an XL and am much happier. I basically had to be game on all the time and commit super hard forward in order to get enough grip. Which is scary if you ride extremely steep skiddy stuff like I do. And requires pretty extreme lean angles to generate grip and exit speed on flatter corners. The XL with longer chainstays and a stupid tall riser bar was the ticket for me. Much more balanced
I suspected that might be the case. When I run some numbers, my XXL Stumpy Evo (also with stupid high stem and bar) is pretty similar in proportions to many well reviewed bikes in size L for 6’ reviewers.
Then again, this new one has substantially longer chainstays, so that might well negate that need to get forward.
Either way, the taller stack heights are awesome for us tall folks.
I have always liked what Nicolai was doing, and they have done some great improvements to this version.
Based off of old interviews with Chris Porter, I was expecting to be the next Geometron to be single pivot w/ spherical bearings and a linkage driven fork with a custom EXT shock