The GSD and HSD wouldn't be nearly so useful without their impressive hauling abilities. Whether you're taking the kids to school, doing the weekly grocery run, or transporting materials for a home improvement project, the ability to carry heavy loads is essential.
But as you can imagine, carrying heavy loads at high speeds—and stopping all that weight once it's in motion—puts enormous strain on a bike's frame and fork. And while making cool bikes is important to us, making safe bikes is an even higher priority. That's why we put the GSD and HSD through rigorous testing to prove that they're safe and reliable up to the claimed load limit.
In this article, we'll tell you everything you ever wanted to know about how we test our bikes. By the time you're done reading, we hope you'll understand what goes into our claim that the GSD and HSD can safely carry your most precious cargo.
What are the load limits for the GSD and HSD?
We've designed and tested the GSD and HSD to the following load limits:
- GSD: 200 kg (440 lb) Maximum Gross Vehicle Weight (MGVW)
- HSD: 170 kg (374 lb) MGVW

Bike = weight of the bike plus batteries; Rider(s) = weight of the cyclist and any passengers
The MGVW includes the weight of the bike and the rider, plus any accessories, cargo, and/or passengers.
How about the load limits for the rear rack?
The rear racks have been tested, too. Here are their capacities:
- GSD: The extra-strong frame-integrated rear rack effectively has no load limit, as long as the bike's overall MGVW is observed.
- HSD: 60 kg (132 lb)
How do we know these loads are safe?
In short, because we designed these load limits into the bikes from the very beginning, and then ruthlessly tested the bikes for strength and durability at every step along the way.
Tell me more. How does Tern's testing process work?
We start by defining the limits under which the bike will operate, including:
- The bike's cargo capacity,
- The maximum weight of the rider (120 kg [264 lb] for both GSD and HSD), and
- The terrain where the bike is permitted to be used.
With these limits in mind, we use specialized software to simulate the stresses we expect the bike's frame and fork to face. The software helps get us in the right ballpark before we start making real prototypes.
Next, we make and ride a series of prototype bikes. We typically put a few thousand miles on these, making improvements with each new prototype design.
To make sure the product development team gets well-rounded feedback from all kinds of riders, we encourage team members organization-wide to ride these bikes. Our Bike to Work program provides incentives and support for team members who commute to work using our bikes, including models still in development. Feedback from Tern team riders across a wide variety of roles helps the product development team make improvements to the initial design.
After this lengthy iterative design process, we begin lab testing the frame and fork to ensure that they can withstand the forces associated with the claimed weight capacity. We perform multiple rounds of internal testing on-site at our factory using the relevant testing standard (more on that later).
During internal testing, we generally try to "test to destruction" to identify the weakest parts of the frame or fork. However, a few of our recent frames have just been too strong for that—and at that point, our lab turns the machines off.
Next, we move on to even more demanding testing at an external laboratory. For the GSD and HSD, we worked with EFBE Pruftechnik, a German company that is an international leader in bike durability testing.