Hi all,
I’ve been looking at the Tantan FM121 as a potential frame for my next build. It looks good and seems to check a lot of boxes for a full-suspension setup. However, after taking a closer look at the design, I can’t help but notice something about the rear triangle that raises some concerns about its durability and functionality.
Does the Geometry Add Too Much Stress?
From what I can see, the seat stays look relatively short, while the swingarm appears longer than expected, with a flatter overall angle. This design could cause the swingarm to travel in a larger radius than the rear triangle, which might not align well with the suspension’s intended motion. Can anyone who has this frame test if you disassemble the swingarm and the rear triangle if they move the same radius.
This mismatch could lead to some flex and stress in the rear triangle. If the swingarm is forced to move differently than the linkage was designed for, it could create excessive tension and strain on the rear end of the frame.
Potential for Restricted Movement
Another point I’m concerned about is how this might affect the frame’s ability to move freely. With the geometry as it appears, the rear triangle might be under constant stress, making it harder for the suspension to pivot smoothly. Did anyone of you check if you can move the rear triangle freely if the Frame is assembled without a rear suspension because it should move without any resistance to the whole 120mm.
This could result in:
Stiff or restricted movement at the pivot points.
Reduced suspension performance, especially on technical terrain.
Long-Term Durability Questions
What worries me most is the possibility of long-term wear and tear, because if the rear triangle is under permanent tension the frame is more likely to crack.
Has Anyone Experienced This?
For those who already own the FM121, I’d love to hear your thoughts. Does the rear triangle’s geometry hold up well in practice, or have you noticed any issues with flex, stiffness, or wear? Does the rear triangle move smoothly, or does it feel tensioned?
I’m still considering this frame, but these potential concerns have me hesitating. If you’ve built or ridden the FM121, please share your experiences .
Thanks in advance
