Home Brompton Shifting problem #189

Shifting problem #189

by Petrelli

A rider is having some shifting issues between the gear 3 & 4. After some testing and inspections, we found the tensioner in a whole was “pushed out”. The caused of the shifting issue was a wrong flange bolt was being used to secure the wheel to the bike. The tensioner (body) is suppose to sit flush to the side of the Brompton rear triangle. There should be enough room for the wheel’s safety catcher and the bolt that secures the wheel to the rear triangle within┬áthe tensioner .

The gap between the red and blue line was the additional gap created by the flange nut.

The gap between the orange and red lines are the thickness of the safety catcher, the tensioner is designed to have such thickness included within. The additional gap created by the bolt’s flange, between the red and blue lines (about 2mm), are pushing the tensioner further out from the frame. This would have an impact on the tensioner wheels’ travelling range. Hence, bad shifting experience.

What did we do to make it works?

Since the wrong nut was being used, all we had to do was to replace the nut with a normal hex nut that is no thinker than 8mm.

Once we remove the tensioner, we found a flange nut is being used.

Instead of using the flange bolt, we put on a regular bolt to it.

After swapping out the flange nut with a normal nut, the tensioner can sit flush on the Brompton rear triangle.

Job done and its good to ride again!


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