In this blog post we explain the design intent of the GMX+, our bottom up, redesign of an off-road bikepacking platform. It has definitely taken some time for our community to understand the very specific geometry we have arrived at after years of in-the-field testing in some of the toughest riding conditions on the planet. What follows applies to both the steel and titanium GMX+ bikes, which have the same geometry.
To start, we should mention that we have not just thrown a bike together from a back-of-the-napkin sketch. We have some credentials in this space that we are very proud of. Over the last five years, the GMX+ geometry has been tested, refined and proven over thousands of kilometers of bikepacking racing and touring in remote outback Australia, and elsewhere around the world. We're lucky to have some great ambassadors who have proven the geometry works on some impressive rides. Each week we hear from customers who have ticked off another rugged, bucket list cycling adventure thanks to the GMX+.
Yes, It is true! The GMX+ is a big bike. It's a long bike. But there are very good reasons for this. A long wheelbase is beneficial for control on rough corrugations, sand and river stones. It also results in a super stable platform for both climbing and high-speed descending especially when carrying a substantial load.
We regularly see comments about the long reach on the GMX+ and so we would like to address that topic here. Comparing geometry charts, the reach is certainly longer than other bike models in the same segment. But, when analysing reach it's important to consider both stem length (and to a lesser extent, bar sweep back) and seat tube angle.
Geometry charts and comparison websites like Bikeinsights.com do not normalise their outputs for stem length. The GMX+ is designed to be paired with a short stem and the Curve Walmer Bar, which has some back sweep. Both serve to shorten the effective reach. As an example, for a complete XL GMX+ (or XXL in titanium), we would specify nothing longer than a 60 mm stem - going shorter is totally fine, too.
Another element to consider when investigating reach is seat tube angle. The steep seat tube angle on the GMX+ moves the riding position forward, more forward than many bikes in its category, again reducing the effective reach. We've found this position beneficial for endurance riding in our years of testing.
Next on the list is stack height. The GMX+ is not designed to be an Australian version of a Salsa Fargo. If you're looking to emulate the tall stack, drop bar setup offered by a Salsa Fargo, perhaps the GMX+ will not be for you. Adding more than 40 mm of spacers under the stem is not recommended on a carbon steerer.
The GMX+ stance is longer and lower than most bikes in its segment but this uniquely allows three modes - a drop bar or flat bar setup which is reasonably low, or a more relaxed and upright set up with a riser bar (like an Oddmonē Bar) without getting too high. The GMX+ in this third mode is a great, relaxed and upright bikepacking set up. We would love to see more bikes in this mode kitted out with baskets.
We've also deliberately designed the GMX+ with a high standover to maximise frame bag and water-carrying space, critical for touring in more remote places we love to ride. A large central triangle is important for maximising load-carrying capacity.
As always, we're super happy to discuss the sizing of our bikes with you. With a few measurements taken from a your current setup, we'll be able to suggest the best size for you. If you'd like to chat more about the GMX+ Titanium and GMX+ Steel get in touch with our sales team at: sales@curvecycling.com