Perhaps noticeable to regular readers is that I rarely write about my folding bike Bino these days. Unfortunately, as of this writing, not all is well with my little blue Dahon Vitesse.
It would be relatively easy and straightforward for me to fix things like the brakes, drivetrain, or touch points. However, when it comes to folding bikes, they all require some sort of maintenance at the frame level, unlike most non-folding bicycles. With the myriad ways of folding a bicycle into a smaller package, many of them proprietary, this isn’t always as straightforward or as easy as it looks.
As one of the larger players in the folding bicycle industry, Tern has published guidelines on what to look for regarding their bikes’ frames.
For Bino, there was a bit of guesswork needed. Dahon isn’t as strong as its sibling company Tern with making customers and owners aware of folding bike frame maintenance, and it doesn’t help that Dahon made a LOT of versions and refinements of the basic main frame joint and clamp mechanism. Fortunately, as a 2013 Vitesse, Bino was made around the time Dahon and Tern “made amends” (the particulars of which make for a very long story), with the two consolidating bike manufacture under the company Mobility Holdings Ltd. Among Tern’s lineup, Bino is closest in frame design to the entry-level Link B- and C-series bikes.
SO WHAT EXACTLY IS WRONG WITH BINO?
At best guess, roughly 80% of folding bikes are patterned against Dahon’s original design of breaking the main frame tube in half, and installing a hinge and clamping system to join the two halves together as a solid, rideable bicycle.
To provide the clamping effect, the main frame hinge and latch mechanism uses special bolts, hinge pins, and threaded rods. Quite obviously, riding around with a loose main frame joint is a recipe for potential disaster.
Adjusting the tension of the mechanism is done by turning the hexagonal rod that lives underneath the main frame lever with a 6 mm open wrench. If the lever opens or closes too easily and with no resistance, the mechanism is too loose. With correct tension, it should take at least three fingers to open the lever, and the heel of your palm to close it. Backing out the hexagonal rod by counterclockwise rotation increases the mechanism’s tension and makes the frame more solid.
By design, the hexagonal rod should have enough screw threads along its length to sufficiently tighten the entire main frame hinge without unscrewing from the joint lever completely. This is no longer the case with Bino — perhaps because of the looseness that developed at the main frame hinge pins themselves. Even with the hexagonal rod barely having any screw thread left to hold it in, Bino’s frame is no longer as solid as it used to be.
It’s not as if this cannot be fixed. One upside to Dahon and Tern’s market ubiquity is that spares are available, if you know where to find them. My plan is to replace the old main frame hinge parts and fully restore frame stiffness.
the accidental randonneur 