Review: The Geometron G1 is Designed to Be Future-Proof & Adapatable

As for the 29er part? Well, everyone's wrong about something.

After Chris's company, Mojo Suspension, parted ways with Fox, Chris setup Mojo Rising with six staff, focusing on Geometron bikes and distributing Formula and EXT suspension.

Until recently there were three options in the Geometron line: the G13, G15 and G16. These have 130mm, 145mm and 155mm of travel, respectively (although the G16 can be run with 175mm travel with a longer shock). The G1 was developed in 2019, and while the name of the other bikes indicates the travel, the "1" in G1 refers to the idea that it's one bike to do everything. According to Chris, Mojo Rising staff were riding the longer travel G16 for everything including long cross-country rides, and you don't need less travel for less technical terrain, just faster-rolling tires.

The G1's "modular" design means it can provide 162mm or 175mm of rear travel with the same shock; accommodate forks from 160-200mm, plus any wheel size configuration you like and a choice of three chainstay length options. With all this adjustability it's designed to be future-proof and adaptable enough for everything - just as long as your idea of everything doesn't involve low weight.

So sure are they that the G1 is all you need, Nicolai no longer make the G13, G15 or G16. "We can make it fit and work for more people in more types of situations," Chris tells me "The G1 is just better!"

Equally important as geometry is the suspension. Mojo Rising worked with Nicolai to fine-tune the kinematics - which have been refined, not revolutionized - since the original Geometron. They've also worked with EXT to provide highly-customized versions of the EXT Storia V3 shock. But perhaps the biggest USP they have for those in the UK is the setup/demo rides and service they offer.

Mojo Riding staff can set up the bike with you from their HQ near Monmouth before heading out for a test loop, during which you can try out different spring rates and suspension settings, geometry configurations, components and even different frame sizes. Can you imagine that from a mainstream brand? Having done this myself with the G1, the experience they have from setting up hundreds of Geometrons for a range of customers, plus the trail-side perspective on your riding, can be immensely valuable even for someone who's confident and experienced setting up bikes for themselves.

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Construction and Features


The G1's frame is all about options. The interchangeable seat stay mutator chips act like conventional flip chips in that they alter the ride height and frame angles simultaneously, except by swapping out chips of different lengths they can theoretically offer eight ride height options. These can be used to compensate for a 27.5" or 29" rear wheel without affecting the geometry, or can be used to change the BB height and frame angles interdependently of wheel size.

The chainstay mutator offers three options for the chainstay length (446mm, 453mm or 458mm). The stock configuration changes by frame size, but there's nothing to stop you running any chainstay length on any frame. The chainstay mutators also affect the BB drop slightly, so it's recommended to change the seat stay and chainstay mutators together if you want to preserve the BB height. This can get pretty complicated, but this spreadsheet on Geometron's website shows all the combinations and their effects.

The shock link has two eyelet positions, offering 162mm or 175mm of travel. The longer travel setting is also slightly more progressive, so the Mojo Rising staff generally recommend the 175mm setting with more sag and similar mid-end stroke support. As if that weren't enough, the G1 is available with an external lower headset cup which allows it to run a 27.5" front wheel with the same geometry. So 27.5", mullet and full 29" setups can be accommodated without affecting the geometry (unless you want to). In theory, you could even run a 27.5" front wheel with a 29" rear, though that's not recommended.


The shock is mounted on spherical bearings which allow the shock to move more freely with less side-loading, and so less friction, as the frame flexes. Cable routing is fully external (except for the dropper cable), with custom aluminum clasps to hold the cables in place. No zip-ties here.



The frame is constructed from 7020-T6 aluminum for its high tensile strength. The raw frame isn't afraid to show off its flat scaled welds, which are produced with a very slow welding speed and multiple passes, which Geometron claim reduces distortion and improves longevity and strength. Less visible are the rubber seals in the bearing preload caps, which are designed to prevent water ingress and improve the longevity of the pivot bearings.

The frame has an industrial, even overbuilt feel to it. The rear thru-axle has a hexagonal nut so it can be used with a spanner or a 6mm Allen key, the seat stay mutator chips are each held in place with two long steel bolts and the reinforcement around the head tube, shock mount and bottom bracket are seriously substantial. I didn't weigh the frame on its own, but aside from the fork the bike I tested has a reasonably light build so a lot of the 37.7 lb / 17.1 kg weight is in the frame.


One feature which is missing is a bottle cage, but on the XL there is space to fit one in front of the shock mount if you get creative. It's also worth noting that tire clearance is relatively tight. The bike is pictured with 2.6" Schwalbe Eddy Current rear tire on a 25mm rim (actual tire width was 64mm or 2.52"), which is a tight fit.

Geometry & Sizing

Because the G1's geometry is so adaptable the above table is really just a starting point. On my XL I measured the BB height at 335mm from the floor. The head angle was a little steeper than stock due to the short axle-to-crown length of the MORC 36 dual crown fork, measuring around 63-degrees depending on how the fork was setup. I stuck with the 453mm chanistay setting throughout testing, but swapped back and forth between 27.5" and 29" rear wheels using different seatstay mutators to maintain the same BB height.

At 190cm tall, I'm on the border between the "longest" (large) and "extra longest" (XL) frame size. "We usually set up both large and XL for a rider of your height to try out," Chris told me, "Or on a ‘distance sell' we would probably spend a bit of time on the phone checking measurements on the current bike and body measurements. Most people at that height are sizing up." Chris also added that clipped-in riders (like me) are more likely to size up as they typically ride more forward.

I've ridden XXL and a Large Geometrons in the past and to a large extent it's possible to adapt to all three. Though there were big time gaps between riding each one, I'd say the XXL was too much work for me when it comes time to manual and hop over trail obstacles. The Large felt big enough when I rode one a few years ago, though its numbers are comparable to a modern XL enduro bike and I'm not sure which suits me better now between the L and XL.

Suspension Design

The G1 uses a Horst-link arrangement, which delivers 33% progression from start to finish in the 175mm setting, and 30% at 162mm travel. That's on the more progressive side, which plays nicely with coil shocks. The leverage ratio drops off smoothly throughout the stroke, resulting in a consistent increase in wheel rate (the suspension stiffness measured at the wheel) throughout the travel.


There's just over 100% anti-squat at sag which keeps the suspension from bobbing too much on climbs, though there's slightly more movement than some enduro bikes with higher levels of anti-squat, like the Privateer 161.

The custom-tuned EXT Storia V3 shock is set apart from the standard unit with its coil negative spring inside the damper in place of an elastomer top-out bumper. In the absence of the main spring, this pushes the shock into its travel a few millimetres. The preload on the main spring can then be balanced against this and so adjust the ride height without introducing any breakaway force like you'd get when using preload on a conventional shock. The negative spring also counteracts the spring force coming from the nitrogen charge behind the IFP, so there's zero breakaway force to overcome to get the shock moving from the start of the travel aside from friction. Chris recommends running the preload light enough that the shock sits into its travel under bike weight, but extends to the point where the main spring has no preload and goes loose when the bike is lifted off the ground and the weight of the rear wheel acts to extend the shock.

This means the "positive travel" measured from how the bike sits under its own weight will be less than fully extended, but the suspension has the ability to extend further when the rider pulls the bike up or the rebound overshoots. In my case, the bike was set to the 175mm travel setting, but about 10mm of travel is taken up just under bike weight. The 335mm bottom bracket height was measured under "bike sag".

The shock has a hydraulic bottom-out circuit, which progressively increases compression damping in the last 11mm of shock stroke (25mm of wheel travel) to resist bottom-out. This allows a small bottom-out bumper to be used. It also gets custom valving for the G1, with lighter low-mid speed rebound valving to allow faster recovery. Chris claims the negative spring allows the rebound to be set faster by resisting rebound before top-out is reached. The low-speed rebound is externally adjustable by hand, the low-speed compression requires an Allen key and the high-speed compression requires a spanner for adjustment. A climb switch closes off the low-speed compression to give a moderately-firm pedaling platform which easily opens up over larger bumps.

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There's no such thing as a stock build with the G1. The suggested build kits listed on the website are there to stop customers being overwhelmed with choice, but customers are encouraged to order off-menu; for example, you can have a 170mm Formula Selva or EXT Era fork, Hope or Formula brakes or supply some of your own parts.

One thing on my test bike that might be hard to get hold of is the fork. The MORC 36 kit adapts a Fox 36 lower and damper with dual-crown upper tubes and offset-adjustable crowns (MORC stands for Mojo Offset Reduction Crown). They can be run with 41.5, 44 or 46.5mm offset, and are claimed to increase stiffness. The longer upper tubes also provide room for Mojo to go to town on a custom high-volume air spring. The lower compression ratios in both positive and negative chambers make for a very linear spring curve, with ample room to adjust the end-stroke progression with volume spacers. Separate valves for the positive and negative chambers allow the ride height and off the top suppleness to be fine-tuned via the difference in pressure between the positive and negative spring. The fork works best with the negative spring over-pressurized by at least 10psi, which causes the fork to suck down into its travel by about 20mm,leaving only around 150mm of usable travel to play with and a short axle-to-crown length.

One component choice which may stand out is the 2.6" Schwalbe Eddy Current rear tire. In order to compare 27.5" and 29" rear wheels I needed tires with identical specs in both sizes, and the Eddy Current was the only tire I could get hold of which fitted the bill. As it turned out, the true width was closer to 2.5", which worked fine on a 25mm rim.

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This setup created a better balance when riding aggressively - over the front and pushing into corners. But the firmer fork made it more important to consciously weight the front wheel on flat terrain.

I spent a lot of time swapping between 27.5" and 29" rear wheels, using seatstay mutators to maintain the same geometry, to find out what difference the mullet makes (feature to come). As a result I didn't experiment with the adjustable offset (I kept it at 46.5mm), with the longer of two stem length options (32.5mm) and stuck with the 453mm chainstay.

Tire pressures were 22-24psi front, 26-27psi rear.

Climbing

How does a 17.1 kg bike with a dual-crown fork climb? Much better than you might think.

Let's start with the fork. I didn't find any climbs where I ride in South Wales where the steering limit of the fork made it impossible to get round. That said, if you live somewhere with tight Alpine switchbacks this may be a problem. And on technical climbs when the wheel slipped out I found myself running into steering lock when trying to regain balance on a couple of occasions. Turning around on a fire road isn't easy either. The 36 fork stanchions are closer together than purpose-built dual crown forks which, combined with the long wheelbase, means the turning circle is wide. But during normal riding this is rarely an issue.

As for the weight, it's maybe a kilogram heavier than an average XL enduro bike with similar tires and coil shock. For a bike and rider weighing 100Kg combined, that's 1% more weight to bring up the hills, so it'll take 1% more power or 1% time. I'm not trying to tell you the weight is a good thing, just that it's not as big a deal as some may think.

It really doesn't feel especially heavy once you get pedaling. What you can feel is the position is super comfortable, with the hips nicely over the bottom bracket when attacking steep climbs. And thanks to the long reach, the cockpit still feels nice and roomy, so my shoulders and arms were relaxed. There's enough anti-squat to keep the suspension from bobbing much when pedalling normally, but the suspension is very free to move when pedaling over bumps. It's not the snappiest when stamping on the pedals, but you can always flip the climb switch if you want a firmer feel. Leave it open and the G1 delivers loads of traction and composure when tackling rough climbs. The steep seat angle means you can remain seated to better manage traction on the steepest climbs around. So while you may get to the top a few seconds later than on a lighter bike, you'll likely get there without having to push.

To illustrate the point, I rode the same steep climb on a Focus Jam, a 150mm-travel trail bike, and the G1 on the same day. The Geometron made the climb much easier because I didn't have to waste energy hunching forward or getting out of the saddle to stop the front wheel lifting.

The slack head angle means there is some wheel flop when turning tight at slow speeds (where the steering creates a force away from straight ahead), but I never find this a problem.

Descending

I spent a lot of time riding the G1 as fast as I could through tight and fast turns to figure out the difference in handling between the full 29" and mullet setup. With either rear wheel, the G1 was remarkably agile in the turns if ridden aggressively. That wheel flop due to the slack head angle means the steering "wants" to tip into the turns, while the low bottom bracket helps it to lean in and out of the corners more quickly. After getting used to the bike I was able to really push on, hitting familiar alternating berms harder than I had before. When pushing into these short, sharp turns there was plenty of support to push against, but with the fast rebound tune the bike would almost jump from one turn to the next. It's not uncontrolled, but there's definitely a springy feel when pushing off short berms.

The long front-center means you can't be shy about getting your weight over the front, otherwise the front wheel is too lightly loaded and won't grip well. This makes the G1 hard to handle if you ride it timidly or hang off the back. But bend your elbows and get your weight forwards and it will reward you with lots of grip and stability, particularly in rough, rutted or steep turns. In an ideal world, you'd want a 50:50 weight distribution between the wheels, and the long front-center means you have to put more weight on your hands to achieve this. But with your weight halfway between the axles, there's more room in front of you with a longer bike, which means the bike pitches and "trips up" less when braking or hitting bumps, and the slack head angle and high trail figure mean the front never tries to tuck or jackknife. For me this makes it easier to "trust in the front," which means I stay tall and centered on the bike when things get steep and gnarly, resulting in better front-end grip than a shorter bike, where I'm more likely to hang off the back.


On the other hand, when I was having an off day, riding tight or timid, the XL G1 can be a handful. This is why some riders at my height might want to size down to a Large, and if I was considering buying a G1, I'd arrange to try both sizes on the same day.

While cornering takes some getting used to, it's when trucking over rough terrain where the G1 is in its element. The rougher, the more hectic, the better. Small bump sensitivity is superb, so the bike takes the sting out of all the small chatter and sticks the wheels to the floor. And when the rear wheel is unweighted, for example when braking or on the backside of bumps, the extra room to extend on rebound allows it to stay in contact with the ground better, which helps to maintain control.

While I've never back-to-back tested spherical bearings against normal bushings, when hammering through a pinball rock section I've ridden countless times, the bike as a whole works so well I could be persuaded they were doing their job. The extra weight of the frame no doubt helps a little in these situations too, as anyone who's ridden an e-bike will know.

The setup Chris suggested with the slightly softer 450lb/in spring and firmer HSC is all about traction and support, but less about comfort. Inevitably, when hitting square-edge hits it sometimes transmits a bit more feedback than you might get from typical digressive compression tunes with less high-speed compression. This seems like a small price to pay though. Despite the firmer high-speed damping and bottom-out circuit, I still I found the bottom of the travel a few times, but not harshly.

The MORC 36 fork wasn't quite as impressive. When setup with enough negative pressure to make it nice and soft off the top, it's only serving up around 150mm of travel. I did try using less pressure in the negative to get it to sit a bit higher, but this ruined the linear feel which is at odds with the rear end. After increasing pressures in both chambers and speeding up the rebound on Chris' recommendation, the fork provided good support and traction, but with the RC2 damper and firm mid-end travel feel it isn't exactly comfortable or forgiving for long descents, particularly when compared to the 170-180mm travel forks I'm used to. But, as with the bike as a whole, if you ride it hard it makes more sense. The fast rebound helps it deal with high frequency bumps without bogging down at all.

The low sagged BB height and long wheelbase make it pretty easy to sump out the chainring on steep rock steps, so a little more care is required on awkward terrain. Clipping pedals is easily done too, so the G1 prefers carving corners and carrying speed over squaring them off and snatching pedal strokes in between.

And while the attention to detail as far as suspension performance is second to none, it's not as refined in some other ways. Despite the coil negative spring, the lack of an elastomer top-out bumper means that, especially if you ride clipped-in, it tops-out with a clunk when hopping over big obstacles like tree stumps. And when rattling over rough terrain there is more chain noise than most modern bikes, even with the derailleur's clutch on.

How does it compare?

I've spent a lot of time on the 161 over the past year, so most of the trails I rode on the G1 I've also ridden on the Privateer. Like the G1, it's a bike for people who aren't too fussed about weight but want new school geometry. My 161 with a Fox 38, alloy wheels and Schwalbe SuperGravity tires weighs 16.3 kg, so a little lighter than the G1. The 161 has an even steeper seat angle (80 degrees) and considerably more anti-squat, which makes it feel a bit more "sporty" when sprinting or mashing the pedals on the steepest climbs. As I said, the G1 is far from inefficient though, and 79-degrees is plenty steep enough, but if faced with a long climb I'd still prefer the Privateer.

The XL Privateer is only 15mm shorter in the front-center and has the same chainstay length, but it feels a bit more lively on the trail and demands a bit less proactivity from the rider. The longer stem (40mm) and slightly shorter front end mean I don't have to remind myself as often to keep plenty of weigh over the front when riding flatter trails. The flip side is the G1 has more of a feeling of steering from behind the front wheel with its shorter stem and slightly slacker head angle, which makes it feel that bit more unshakable when tackling big rocks or steep catch berms. Ultimately, this comparison shows how far other brands have come: the 161 has near-identical BB height, chainstay length and seat angle, while the wheelbase of the XL Privateer falls in between the Large and XL G1. As a result, the handling is not worlds apart.

The rear suspension on the G1 is a little more planted at the rear, although the Fox 38 offers plenty of stiffness and early-travel sensitivity without the steering lock and travel limitations of the MORC 36.

Technical Report


Formula Cura 4 brakes: After a bleed the Cura 4 brakes were impressively powerful, with a short free stroke and a sharp lever feel. I'm a big fan of the more punchy bite point over the more modulated feel of a Code, and the bite-point consistency was faultless. The only downside is that you couldn't squeeze a pensioner's payslip between the pads and disc, so setting them up without any scuffing is next to impossible.

DT Swiss EX471 rims: 25mm wide rims are still ride-able, even when running a 2.6" tire on the rear. But I had to add a psi or two to stop the tires squirming in turns, which I rarely find a problem with 30mm rims even at pressures where I'm occasionally hitting the rim on rocks.

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Pinkbike's Take

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Reviews and Tech Reviews Enduro Bikes Geometron Nicolai Geometron G1