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Accurate Triumph 650 Rear Wheel Alignment Using Mason Line

Poor rear wheel alignment results in excessive wear to rear tire, sprockets, and chain.

The method that's given me the most accurate alignment results is using mason line.

Advantages

Disadvantages

Materials

Method

  1. Bike on center stand

  2. Begin by fixing the line to a rear tire spoke on the drive side and wrapping it across the back of the tire about seven inches off the ground. A picture-hanging hook tied to the line works great.

    Then, on the timing side, run the line through the center stand and around the front tire tread, keeping the line parallel to the ground. If necessary, adjust the height of the line so that it is as high as possible without fouling the center stand.

    As you go around the front tire, pull the line on the timing side good and tight before going down the drive side, through the center stand, and returning to the rear wheel.

    A finger-sized loop knotted into the line just ahead of the center stand on the drive side makes it easier to keep the line taut while you thread the loose end through the center stand.

    Diagram of rear wheel alignment using mason line.
    Back at the rear tire, pull the line taut, cross over the tire, and wrap it around the TS shock absorber bolt before making several turns around the folded passenger foot peg and securing it with a half-hitch.

    You now have a taut line all the way around the outside of both tires. If it's not taut, go back and teach it.
Shimming string from tires
  1. Next use the shims to space the line away from both front sides of the front tire, and both rear sides of the rear tire.
  1. Carefully, make side-to-side adjustments to the front wheel until the measured distance between the line and both sides of the rear of the front tire are equidistant. I use a 6-inch machinist's rule.

    Measuring gap, front tire

    Once the front wheel is centered between the lines, it should be immobilized, either beforehand using the steering damper if fitted, or afterwards with concrete blocks or wooden blocking.

  2. Now measure the distances between the line and both sides of the rear tire. If they are not equal use the axle adjusters to move the rear wheel side-to-side until it is centered between the lines.

    After this initial alignment, go back and check if the front wheel is still centered between the lines. Re-adjust front and rear wheels if necessary. When both tires are perfectly centered between the lines, they are aligned.
Measuring gap, rear tire
  1. Alignment completed, tighten the axle nuts incrementally to factory-recommended torque: 100 pounds for 1969 T120R.

  2. It doesn't hurt to make a final check after tightening the axle nuts.

  3. Remember to check the tension of the drive chain before you go for a ride on your perfectly aligned Triumph motor bike.
650 Triumph