Hello dear readers. Are you ready?
Buckle your seatbelts, put on your out-of-office. Be sure to prepare a too-carefully-constructed pour-over coffee, or maybe a glass of tap water, and settle in. We are about to embark on a journey together, an unbiased, at times fanciful, long-term review of the GMX+ adventure bike from Curve Cycling.
But first, a quick disclaimer: I have never been very good with the mathematics associated with cycling. I have a Fine Arts degree, not a science, math, or engineering degree that biases left brain thinking. Geometry, angles, and the use of descriptors like “steep” or “slack” are something I hope to get a better grasp on in the future, but they don’t play a huge part in this review. Did I have to google things like “bike geometry for dummies” and “the ultimate guide to bike geo?” I did and for this I have no shame. For those who rely heavily on these numbers and holistic geometric indicators to make their cycling-based decisions, I hope you can read between the lines of the sweet prose herein to get what you need. I paid for this frame with a lot of pennies from the proverbial couch cushions, so rest assured what lays ahead is my completely honest opinion.
What is the GMX+?
According to Melbourne-based framebuilding company, Curve, the GMX and (its successor) the GMX+ were inspired by overlanders in the late 1800s, covering long distances, in the unforgiving terrain of the Australian outback. To draw on these self-sufficiency ethos, Curve wanted to create a frame that would serve as a capable and resilient adventuring platform while also allowing for the advantages of modern technology. The original GMX proved it could withstand the abuse of long distance riding and harsh conditions in multi-day races like the Race to the Rock, a challenging desert route in the heart of Australia. Through this testing came new ideas and improvements, and ultimately, the GMX+ was produced. In true adventure bike style, the GMX+ is built to accommodate flat or drop bars and expands the capabilities of the GMX by accommodating 29+ tires, utilizing boost spacing, and features a t47 bottom bracket shell, all on a frame that’s ultimately a bit slacker (see, there I go with the lingo!). Additionally, there are more mounting options on this second generation version for all the gear and water you could ever wish to strap to it. Since then, we’ve seen the GMX+ present in numerous, long-distance races, proving itself again in Race to the Rock in addition to the Tour Divide and Silk Road Mountain Race.
The GMX+ runs in XXS – XXL, including an Extra-Medium option. The SM-XXL are designed around 29” wheels, and the XXS and XS around 27.5 counterparts. As a smaller-statured person, I appreciate the fact that this frame was designed to be able to carry up to 7 bottles using the various mounts and still utilize a full-size frame bag. To state the obvious, this is a burly bike. Observing the tubing and the welds, I have to say, compared to something you might see at hand-made bicycle shows, functionality seems to have won out over aesthetics. Though cleanly executed, the tube set is large, and the thick welds belie their strength and durability. The GMX+ seemed perfectly suited to the type of riding and exploring I like to do.
Why did I Choose the GMX+?
With the GMX+ I was setting out to solve a problem for myself; one of bikes versus space and also one of terrain. Over the years, I’ve been lucky enough to build a handful of bikes, buying and selling them as different I entertained different interests in different aspects of cycling. Recently, I ended up with two steel bikes that I truly loved and didn’t have any intentions of deviating from. Yet, when my partner and I moved recently, we needed to downsize. Along with her bike, and the occasional bike I might be testing, borrowing, or photographing, we just didn’t have the space for me to have two bikes. I asked myself: could I sell my current fleet and combine them into one? I don’t believe in quiver-killer designs, but this new bike would still have to tick a few boxes.
Ideally, I would have a frame suited to both drops and flat bars. Of course, switching between the two can be rather inconvenient, but sometimes the option is all you need. I wanted something durable, with the ability to carry a lot of gear. On the other hand, I also wanted a bike that would feel nimble and as quick as my legs could make it when stripped down. I’ve always run large tires, and the ability to fit wide tires, but having something that didn’t feel out of place on a smaller tire was a priority. The gravel we ride near my home of Squamish, BC is not what most sane people would even consider “gravel.”
We are either riding on decommissioned or active logging roads. Regardless of their use status, these roads get harsh. Our gravel is mostly what I would describe as rubble, riddled with edges of razor-sharp granite, and potholes that would swallow a smart car. I certainly have friends with more remarkable riding abilities than I, who are able to run more traditional gravel tires with ease, but I’m happy to let the tires make up for any ineptitude when it comes to skill versus the terrain.
So, I took the plunge, sold my bikes to some very stoked folks, shed some tears at their departure, and clicked “check-out” on the Curve website after exchanging a few emails about sizing with the helpful staff over at the shop.
For reference, I’m 5’6″ and have roughly a 29” inseam. I previously rode a 49cm All City Gorilla Monsoon and a size medium Crust Scapegoat. I settled on a size small GMX+ frame.
Set Up Overview
Although the most popular option I have seen out there with the GMX+ is to run it with super wide drop bars (Curve’s own Walmer bars being the widest of the wide and specifically designed for this), I opted for a very fun flat bar to steer this titanium ship. I dropped a line over to Whit at Meriwether Cycles about sourcing a set of his Ti Double Bend Sweeper bars. Not too long after Whit kindly answered a few questions for me, I had in my hands an 800mm, beautifully bent piece of 22.2mm titanium. This also came with a Shimzilla, to accommodate a 31.8 stem clamp. The bars are flat with no rise and sweep back around 19 degrees after going forward. You can now find Whit’s bars through Agave Finishworks.
I like to use big front bags, and with the exception of going with the widest Walmer bar, a flat bar is just the easiest way to make this work. It also allows me to run small tri-bars, or SQ inner bar ends, if I want to provide more hand position options for any really long rides. I’m running a 60mm Salsa Stem, which I plan on bumping to a 70mm. And yes, I know. I need to cut down my steerer tube. I was initially just too afraid to take a saw to an expensive carbon fork.
Fairly inexpensive, reliable, and utilitarian for not a lot of money was the goal. I had a set of Hope Pro 4 hubs, which I laced up to a pair of Chromag Ally Rims. After chatting with a few friends that have had them, I ordered a set of Vittoria Mezcals in a 2.6″. I couldn’t be happier. The tread is just enough for the loose dry summer we’ve had here in BC, and I’ve had no punctures, tears or issues with this setup.
Okay. If you haven’t gathered this already, I am a person of simple pleasures. The majority of my life I’ve had simple mechanical disc brakes and it’s likely I will continue to do so. They work for me (most of the time) and as you can see by the loaded photos, I don’t exactly pack light. In hunting for parts for this build in various corners of the internet, I came upon a set of BB7s and levers for $40 on the buy and sell. Are there sexier options out there? For certain. Do these do what they need? Yes.
Oh my. I do love bike bags. It’s an issue. I tapped my friend Matt over from Vancouver’s HMPL for a couple of new bags for this rig. He took advantage of the bag maker guides that Curve has to sew up a beautiful double zip frame bag, with big oversized zippers. I’ve never run a double zip, and I’m hoping it helps organize my packing a little bit. He also sewed up one of HMPL’s Double Buddy barrel bags (extra big for cameras, layers, and snacks). Both bags are made out of a combination of Challenge Sailcloth Ultra 400 and Challenge Sailcloth Ecopak EPX-200. Light, durable, and with a lot of space. It’s going to be dark and rainy here in British Columbia for the next seven months, so the hi-vis accents are a must. Make sure you check out HMPL for custom work and their in-stock goods.
Okay, this drivetrain is also a bit of a Frankenstein, basically due to the parts I could find at the time. I’ve had good luck with Sram GX on my bikes, and I didn’t particularly feel like deviating. At the time, I couldn’t find a GX shifter and derailleur, so again I went hunting through the local classifieds. I picked up the cassette, shifter, derailleur and chain for $200 off of Craigslist.
The cassette and chain are Sram GX, the derailleur is SX and the shifter is NX. Crazy as that sounds— it all works. The SX and NX feel plasticky and like they might turn to dust if you look at them wrong, but for all the trips and riding I’ve done this summer, it has all worked seamlessly, even shifting under load up steep coastal grades. Once we are done with our wet and grimy winter, I’ll be swapping out to all GX. Spinning the whole system are some Race Face Aeffect R cranks, and a Race Face 36t chainring. I like the Aeffect R because they are simple, fairly light and inexpensive (and, the chainring is purple!). I decided to go with Chris King bottom bracket for the GMX+. They are pricey, but I’ve become a CK BB disciple over the years and I don’t think I’ll go with anything else in the future.
Parts Upgrades For the Future?
There are of course some things I would change in the future, bar a recession, inflation, and in general, just being a bit of a cheap chap when it comes to bike parts. This is a fancier frame than I could have ever imagined owning, and I appreciate the less glamorous parts that have allowed me to ride it.
Rims: Would I love to eventually be rolling on a pair of carbon hoops? Of course, these Chromags are heavy as sin.
Brakes: Paul Love levers? The best I’ve ever used, the only set I’ve had were accidentally sold to me way too cheap, and I didn’t know what a deal I had scored. Honestly, I’ll just keep the BB7s. As our lord Bicycle Pubes so aptly stated, “BB7s are probably fine”.
Cranks: Dreaming? EEwings of course. Reality? Some used carbon cranks off of the buy and sell are a more likely possibility.
Drivetrain: I’ll shortly be replacing the stress-inducing plastic shifter and derailleur currently on this build, but I would love to eventually try out the AXS upgrade on here, since I don’t have enough tiny expensive things that I need to charge in my life.
Shout out to my friend Zach over at Corsa cycles for putting this bike together after I showed up with a frame and bag of parts!
Real World Riding
I’ve spent the last five months or so riding the GMX+ in a variety of conditions and terrains, and I’ve been honestly quite happy with it overall. Am I happy because I don’t have any other bikes, and don’t really have a choice? Well yes, and there are little things that bother me, but that’s always been the case with any bike. So far, I’ve taken this bike for our weekly local gravel meetup rides, which tend to be fast-paced, and short distances, rain or shine. Did the big tires and beefy frame feel too sluggish to keep up? Not at all.
I’ve taken the GMX+ on completely loaded down (and I mean the heaviest-bike-I’ve-ever-ridden type of loaded down) multi-day, bike-to-climbing trips. It has carried me on 100km+ rides during solo long weekends, with confidence, and so far without a single mechanical, or question mark. Can it also do beer or coffee runs, and flat pedal-fitted rides down to the beach? Yes indeed. Just because it’s titanium doesn’t mean you need to go fast.
All the types of riding above, for where I live, usually involve thousands of meters of steep climbing (with the exception of the aforementioned beer and coffee spins) and the GMX+ has proved more than capable of delivering. Two very clear things come to mind when I think of the riding and handling characteristics of this bike.
Under a light load, it seems to accelerate incredibly fast for its size. I can’t think of another term besides zippy. And that “zippiness” doesn’t come at a sacrifice of the bike feeling stable, as the only time I notice what I would describe as twitchiness is riding one-handed while snacking. Things tend to get a bit squirrely then. Likely, this is more due to the wide bars than anything else. The oversized tubing, seat post, and T47 bottom bracket all have a relatively stiff feel, but this does translate to feeling a lot of power from each pedal stroke.
It did take me a few rides to get used to how the frame feels under a heavy load. I didn’t think I really noticed a difference in titanium, but when fully loaded, the responses to rider control shift a bit. It, by no means, becomes sluggish but takes a bit more thought in handling from the rider. Ultimately, I have found that the GMX+ responds just as well as any other frame I’ve ridden, but you do feel a subtle difference in the way the material absorbs and responds to rider input when heavily loaded in rough terrain.
This frame is slacker than the GXR, and the 55mm fork offset implies stability at speed, but does also feel fairly agile in more technical and challenging terrain. I’ve found this to be fairly accurate. When hitting that oh-so-sweet combination of high speeds, on a loaded ride, the GMX+ doesn’t get knocked off course. Rather, it mows over the terrain. It is happiest when it gets moving. This is the first bike with 29” wheels I’ve ridden and I did notice the handling difference so commonly talked about, in tight terrain. The wheelbase sits between my two previous bikes, so while not the longest bike I’ve ridden, the larger wheel size took some getting used to though, any reservations are far out shadowed by how well the chasis rolls.
Fork: Is Carbon a Compromise?
Consider the fork. It’s been a work in progress mentally, but I now love how confident I feel with this fork. I was initially really hesitant to go with carbon, knowing that I like to strap things all over the place on loaded trips and care needs to be taken when it comes to protecting carbon. For my style of riding, the fork is really the only place I might truly gripe. However, none of my complaints really are to do with the actual construction or design. The number of mounts is fantastic, but I miss having fork crown and lower rack mounting points. Obviously, this is due to the nature of the load-carrying capacity, but it narrows down front bag, and front rack options. In the future, if I am doing more truly exploration-based riding, I could see getting a custom steel fork made, with endless mounts, and no worries from straps sawing through precious carbon.
I have to say, I’ve been really happy with my choice to try this rig out with flat bars. The flat bars make it feel like a big BMX bike to me. It’s playful, easy to maneuver, and I can accommodate accessories if I ever need to feel fast. I think I will try this setup with drops one day, but not anytime soon, as I’m having too much fun. Cyclists take themselves too seriously, and I usually get a few good chuckles when I roll up to a ride while I’m hanging onto the ends of these 800mm bars. But it’s so great!
Cargo carrying capacity has been a shining point for the GMX+. There are really endless mounts that allow you to mount cargo cages or bottles all over the frame. I’ve used this frame, carrying micro panniers and a small rack on the rear of the bike, three bottles on the main triangle, and cargo cages on the fork. The ability to carry cargo cages or bottles on the rear triangle is also a win. It’s becoming more common, but you still don’t see it on too many bikes. The bottle mounts on the down tube, close to the front wheel, have become my favorites, mostly because they are strange, and my brain doesn’t understand how the tire clearance is possible. If you ride around a lot of cow shit, beware – these bottles do get dirty.
So what do I think? Afterall, this is all just one opinion, and each bike is influenced by the attitude you bring to it. Well, I’m happy. Speed, reliability, shredability, all have me with a smile on my face every time I throw a leg over the GMX+.
If you fancy races, long trips loaded to the nines, and just generally want to have fun on a bike, the GMX+ is worth consideration.
There you have it, I hope you come away entertained, and ideally with some questions answered on whether or not the Curve GMX+ is for you. Ultimately, I feel incredibly privileged to have been able to build this, and I’ve enjoyed my time with this bike so far. It is, after all, just another bike in the world. All that matters for me is where I ride it, who I ride it next to, and ideally, not having any massive mechanicals along the way. Thanks for reading friends.
GMX+ Frameset Details
3Al – 2.5V Aerospace Grade 9 titanium
7x cage mounts
Rear rack mounts
Clearance to 3.0″ tyres (on the 27.5 and 29 models respectively)
1x only (38t max)
T47 Bottom Bracket
31.6 Seat post
Made in Taiwan
Headset: 44/56 zero-stack
Seek 430 Carbon Fork Details
Full carbon construction
12 M5 mounts (6 per side)
1.5” tapered steerer
Load Capacity of 3kg on either side of the fork (6kg total)
The frame ships with a headset, carbon spacers, thru-axles, spare derailleur hanger, bolt-on cable guides, and a curve seat clamp. See more at Curve Cycling!