Swingarm failure - torque arm mounting point

[MC680x0]

Im still scratching my chin on this whole tourque arm thing.
How come then if you should loosen it (both ends ) before you pull back the wheel-------- how come you CAN still pull back the wheel without loosening said arm.
And what exactly is the tourque arm providing tourque against or what tourque is it countering, I always thought it was to stop the caliper spinning around the disk when you brake --- but isnt it bolted in place?

edited out my response: changed my mind !  :eek kebab , you have answered your own question and also seen the results of not having a torque arm or having one that isnt to spec, non OEM, or has been stressed out of normal parameters

try to visualise in math terms...

imagine a triangle made of tough steel rods connected by bolts at each corner. One side is your vertical on the swingarm, one side is from the vertical to the caliper along the swingarm horizontal, and the final side is the torque arm. Now imagine pushing and pulling on the calliper , what do you think is going to happen to the shape of the triangle. Push hard, force, its going to "bend" the triangle and eventually one side is going to bust (or a corner).

Now, undo some of the bolts and the triangle now starts to change its shape, its still a triangle but the angles are changing  -and thus the shape - as you move the corners around pushing and pulling. It moves freely now but there is no rigidity - things can move around the pivots (corners) and so can the calliper !!!.

Tighten up the bolts again and you have a rigid triangle shape. Try to bend it now or apply forces too great, and it will break but under normal parameters the shape remains rigid and the pivots stay where they are (the calliper doesnt move!)

So if one of the sides is weak (a non OEM torque arm or an arm not to spec) then the forces applied when braking are going to try to move that triangle shape and the weak point (the arm) is going to give or a pivot (the mount) is going to shear

When you adjust your chain you are changing the wheelbase and the shape of the triangle; loosening the bolts allows the calliper to rotate slightly around the pivot and bring the triangle into a slightly different shape and moves the torque arm slightly (the swingarm "sides" of the triangle cannot move). Without allowing the calliper to rotate, you are trying to apply those forces to the triangle without allowing the shape to change in reciprocation and thus "blow" the triangle out of shape or make it come loose at the weakest point - a pivot point (the swingarm mount in your case).

Its all very minor adjustments but the sum of the parts is greater.

. Voila!

You have your answer