Sideway movement of the rear wheel

Strida Forum Strida Problems and Answers
19

Hi BSA,

I was actually wrong in my statement about the torque :blush: . And you were right when you wrote that adding a washer would increase the spring preload. The sketch below shows that bolt 373 is actually torqued against axle 340 end. So the cupped spring preload is purely dependant on distance X (spring built-in length).

I think I now have an explanation for the angular movement of the wheel on my bike: the sharp edges of cupped spring 367 eat the surface of the bottom tube and of washer 364 away (as can be seen here), which increases the cupped spring built-in length. These springs are very stiff, which means that a small variation of their built-in length greatly affects their preload.

I have not checked the dimensions of the cupped spring 367, buit I think they are close to these ones: inner diameter: 12.2mm, outer diameter: 28 mm, thickness: 1.25mm, total height: 2.1mm

In a catalogue (http://www.bellevillesprings.com/disc-springs-din-2093.html) you find out that when you compress such a spring by 0.64mm, you achieve a force of 2083 N. If you now compress it by only 0.38mm, the force drops to 1395 N.

So, the wear/deformation that can be stated on both bottom tube and washer 364 will make the preload of the cupped spring drop sensibly.

Looking now to the exploded view of the Strida in the manual, you can see a washer 363 between cupped spring 367 and the bottom tube. According to me, this is a flat washer that prevents the wear of the tube and also increases the preload of the spring. I wonder why they have removed it.

I get mad when I see that such cheap parts and poor design can affect the functioning of this otherwise nice bike. :imp: :imp: :imp:

This poor design has following consequences:

  • Irreversible damage of the aluminium bottom tube.
  • Clicking noise
  • Angular movement of the rear axle + wheel : this can trigger the belt to jump on the flanges of the freewheel and definitively damage the belt.
  • Bad guidance of the rear wheel: it accelerates the wear of the rear tire and causes bike instability.

I sincerely hope that these problems have been solved on the EVO3, as its high price should go together with a high quality level.