Parallel Engineering

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Motorcycle Frame Alignment For All Bikes.

Parallel Engineering

As is the case with other chassis components e.g front forks and rear suspension, for the frame to work at it's best it requires precision manufacture and alignment.

The relationship between the swing arm and steering head axes is critical. Mis-alignment here puts the rear wheel out of line with the vertical and horizontal planes and not parallel to the frame centre line, as the swing arm moves up and down the rear wheel centre line moves left and right relative to the frame centre line and creates instability. It's as if the swingarm bushes are permanently worn out.

Rather than assume dimensions are within effective tolerances it makes sense to accurately check relationships between components prior to assembly. Any discrepancies can be rectified at this stage rather than problems becoming apparent only when the motorcycle is complete and on the road, thus saving time, money and disappointment.

Problems with Classic Motorcycle FramesProblems with Frames

Welded assemblies suffer from distortion. This occurs during the welding process due to concentration of heat and the molten weld pool to which filler is added. As the weld pool cools it shrinks and creates stress and thus distortion within the welded assembly. This also occurs to welded assemblies mounted in production jigs.

Variables in manufacturing also add to the above problems.

Solutions for Classic Motorcycle Frames

The following steps are required to establish complete alignment.

  • Steering head axis and swingarm axis are checked for square in two planes.
  • Swingarm is checked for square and alignment marks are accurately machined to the swinging arm rear wheel adjustment slots.
  • Fixed frame centre line reference point transfered to chassis.
  • Rear wheel is centred to frame centre line.
  • Fork stanchions and yokes are checked and front wheel centred to frame centre line.

On assembly, front and rear wheel centres and axes are now inline and square with each other and the frame centre line.


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