It crossed my mind the other day that the flex I'm feeling when I pull on the handlebars of my mark 3 M-type might be a lot to do with the frame hinge clamp design. I was inspecting it closely and there's no doubt that a lot of flex occurs in that region. I don't think too much has changed in the post-2004 hinge design, basically manufacturing tolerances are extremely loose, the plates have a very small area on the left outer edge where they meet and there's a gap from the top to the bottom due to a slight curvature of the inner surface. When I pull on the bars I can see the gap at the top shrinking, i.e. there's visible flex.
In all other folding bikes I've looked at there's a large contact area that forms a complete circle, i.e. it's buttressed in 360 degrees. This, I'd imagine, is one reason why Bromptons tend not to suffer from creaking in the hinge clamps, not because they're better engineered but because there's a much smaller contact area and that contact area is directly under the clamping plate.
Looking at the post 2004 hinge redesign I'm thinking it ought to flex a little less. . . a fractional improvement would be significant amplified through the length of the stem/handlebar.
Has anyone here who's owned Bromptons with both the old and new hinge types noticed much difference in terms of overall flex?