EFBE TRI-TEST® GRAVITY – The Gold-Standard Test for Gravity Frames
The Remastered Stamina has a lot more going on than the shiny new electrophoretic finish.
Considerable structural changes have been made to the design. When coupled with the even further refined manufacturing process, the result is a frame that can withstand the most demanding riding and come back for more, day after day.
A testament to this is that the Stamina frame passed the rigorous EFBE test protocol. Here we talk in more detail to learn more about what goes into it and get a perspective of the phases the frame needs to pass.
First of all, why test? Objective testing is the basis of the scientific method. Everything outside of that is more or less educated guesswork. Testing done scientifically in a controlled lab setting can validate the tested design, or point out possible shortcomings, and therefore the need for further developmental work.
Can real-life riding conditions (over multiple years of intensive use) be replicated in a tightly controlled lab setting in just a few days? Perhaps not. The forces and stresses that a frame and components are subjected to on the highest levels of riding are very, very hard to quantify and according to the current understanding, no verified data exists on this front. What we can do though, is to test the frame – or other components – according to the strictest testing protocol there is, and that’s exactly what we did.
A Stamina 180 frame was sent to EFBE Prüftechnik GmbH in Germany to go through the EFBE TRI-TEST® GRAVITY (the TRI-TEST also comes in other flavors) which is a test designed specifically for gravity bikes. The test consists of the following;
- Pedaling Forces Fatigue Test
- Vertical Force Fatigue Test
- Head Tube Fatigue Test
- Brake Load Fatigue Test
- Rear Axle Load Fatigue Test
- Lateral Load Fatigue Test
- Maximum Load Test Pedal Load
- Maximum / Overload Test Jump/Drop Load
When going through the list it becomes quickly apparent that the full test forms a demanding decathlon that the frame needs to withstand in order to meet the full criteria. Forces, the direction in which those are applied in and the number of load cycles depends on the test stage in question. Let’s dive in to see what the TRI-TEST® is all about!
The Test Procedure
Before going through the test details, it’s worth going over a bit of elementary physics. Newtons are the units used when quantifying forces. To get a simplified understanding of the situation, you can divide the number of Newtons by 10 to get a corresponding mass in kilos (assuming we are operating in Earth’s gravity field). For example, a force of 1200N would equal roughly a static mass of 120kg. Engineers might be appalled by this dumbed-down approach but a simple calculation like this helps to put the forces used in scale when getting familiar with the testing protocol.
Let’s go through the test stages one by one to see what they entail. In all of the tests, the frame is mounted to the testing rig and the shock is replaced with a rigid member with the suspension set either to 30% (approximately around sag point) or 100% (full compression). A rigid dummy fork is used to connect the headtube to the testing rig to simulate the loads a suspension fork would encounter and transfer to the frame in real riding conditions.
A word of warning though! This section is somewhat technical. Feel free to skip it and jump straight to the conclusions if you wish…
Pedaling Forces Fatigue Test
The test simulates stresses caused by the pedaling forces. Dummy cranks are attached to the bottom bracket at a 45degree angle from a horizontal line. A force of 1300N is applied to the cranks for 100 000 cycles with a frequency of 10Hz or less. The test is similar to that of ISO 4210-6:2014, 4.3, but the forces are greater.
It’s worth pointing out that the pedaling forces simulated are much more than just light spinning. A world-class sprint track cyclist might be able to produce a pedaling force of 1300N, but numbers of this range are unattainable by most mortals.
Vertical Force Fatigue Test
In this test, the frame is mounted from the axles to the rig while a vertical force of 1300N is applied to the seat post with an insertion of 120mm. The loading parameters are nearly identical to the first test: 1300N, 100 000 cycles, and 2-5Hz.
The loads the seat mast area of the frame heavily, and everything below it. A similar loading in real riding conditions would most likely require a year’s worth of laps on a bike park – seated.
Head Tube Fatigue Test
As the name implies, the test is used to strength and fatigue characteristics of the headtube area. A dummy fork is used to mount the headtube while an alternating + 600N/-1200 N test force is applied at the front wheel axle, perpendicular to the steering axis. The rear axle 100,000 load cycles are used once again with a frequency of less than 10Hz.
Brake Load Fatigue Test
This stage stimulates stresses caused by braking with a 203mm rotor. The frame is mounted to the rig from the rear axle and from the head tube with the aid of a dummy fork. An alternating horizontal force of +200N/-400N is applied to the disc brake rotor jig which in turn stresses the disc brake mount, simulating braking action.
Once again, 100,000 load cycles were used with a frequency of 10Hz or less.
Rear Axle Load Fatigue Test
The frame is fixed to the rig from the bottom bracket and from the head tube with the aid of a dummy fork. A vertical force of 2100N is applied to the rear axle for 100,000 cycles with a frequency of 10Hz or less. As opposed to the previous tests, the rear suspension is set to 100%, to simulate a full bottom out situation.
Lateral Load Fatigue Test
The lateral load test simulates a situation in which the frame is loaded heavily in a lateral direction (meaning sideways). A prime example of a corresponding real-world situation would a high-speed berm where a change of direction happens very fast – something Mr. Nation does day in, day out.
The frame is mounted to the rig from the bottom bracket and headtube similarly as in other test stages, while an alternating sideways load of +-400N is applied to the rear axle for 100 000 cycles at 100% suspension travel.
Maximum Load Test Pedal Load
The two most critical areas in frame design are the headtube and bottom bracket area. A sudden failure in either one of these areas can lead to dire consequences. This test verifies that the frame is up for the task when the bottom bracket is loaded heavily. A single-sided static load of 2500N at a lateral angle of 26degrees is applied to a dummy crank arm placed on the 6 o’clock position and then held for 10 seconds.
To pass this test, the frame must not show visible cracks, fractures, or permanent deformation at the point of application greater than 10mm.
Maximum / Overload Test Jump/ Drop Load
Finally, we have “the Big Case test”. The frame is once again supported by the dummy fork and a from the rear axle. The rear axle support fixture is placed 15degrees from the vertical to replicate a situation in which the wheelbase lengthens. A force of 6000N is applied vertically to the dummy crank arm mounted to the bottom bracket and held for 10 seconds.
The passing criteria are the same as in the previous tests, no cracks or deformation greater than 10mm should be observed. It does not end here though! After the test, the frame needs to withstand a force of 1000N applied in the same manner with no brittle fractures or other catastrophic failure modes.
One sentence followed every test stage: “The test was passed.”
Here to Stay
Passing the very demanding EFBE TRI-TEST® doesn’t happen by coincidence. It requires either an overbuilt frame or smart engineering. We rely on the latter. First, the test in question is developed to test downhill bikes which gives some strong hints of its highly demanding nature. Very few enduro frames have been tested this way and even fewer have completed the grueling eight stages of the test which gives it almost a prestigious status.
Thanks to the superior 7075 T6 aircraft aluminum, and our self-developed, and much-refined bonding procedure, the Remastered Stamina is one of the few frames belonging to this rare club.
The aerospace-grade aluminum has nearly 1.5-fold tensile strength compared to the weldable 6000 and 7000-series alloys. The refined frame design, with its internal support structures, keyed headtube inserts, and bigger bonding surface area has only added strength to an already robust design. Besides the base material and the design, the bonding is more than adequately strong to cope with the high demands of modern gravity riding – and passing the EFBE TRI-TEST® with flying colors is a testament to this.
The new Remastered Stamina is here to stay. It combines modern confidence-inspiring geometry with top-of-the-line pedaling efficiency. The Stamina will keep ticking for years to come and will maintain its eye-catching looks thanks to the electrophoretic coating which is one more technology of which we are the first to use in the bicycle industry at this scale.
The Remastered Stamina is available now in Raw Clear or the ever-popular True Gold. Order yours now to enjoy the capabilities of a true modern Super Bike with its 180mm ground-hugging, but still efficient travel.
The Stamina is built to last and backed up by rigorous scientific testing.
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