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Mason line rear-wheel alignment

Aligning the rear sprocket and drive sprocket minimizes sprocket, chain, and rear tire wear.

The method of alignment shown below uses a mason line and shims. The shims hold the line off the tires and the measurements are made of the distance between the line and the tires to obtain equal distances from one side to the other.

Advantages

Disadvantages

Materials

Method

  1. Bike on center stand

  2. Run the line: beginning at the rear tire, fix the line to a spoke. A picture-hanging hook tied to the line is ideal.
    Run the line around the outsides of both tires, threading it beneath the frame and through the center stand on both sides before pulling it tight and securing. My habit is to run the string up the timing side and then back to the rear tire along the drive side.
    Diagram
    When the line is back to the rear tire, I tighten it, beginning back at the front wheel and then pulling it tight across the back of the rear tire. Then I wrap around the end of the TS shock absorber before finishing it off around the folded passenger foot peg with a few turns and a half-hitch.
    A finger-sized loop knotted into the line makes it easier to pull out the slack and tighten the line on the drive side.
    You now have a taut line all the way around the outside of both tires.
  1. Using the four shims, space the line away from the sides of the front and rear tires.
Shimming string from tires
  1. Adjust front wheel from side-to-side until the distance between the rear sidewalls of the front tire and the line is equal on both sides. I use a 6-inch machinist's rule.
    Measuring gap, front tire

    A steering damper is quite useful to hold the front wheel immobile during the remainder of the operation. Before I put a steering damper on Bonnie I used a couple of heavy wooden blocks. Concrete blocks would probably work well.

  2. Measure the distance between the line and the tire on both sides and then use the axle adjusters, move the rear wheel side-to-side until the distance between the rear tire and the line is equal on both sides.

    When the distances between the rear tire and the line on both sides are equal, the front and rear tires are aligned. I make it a practice to re-check the centered-ness of the front wheel between the lines in front, and get back down on the ground and re-check the two sides.
Measuring gap, rear tire
  1. Once the alignment is good, tighten the axle nuts, easy at first on both sides, then torque progressively from one side to the other. 100 pounds.

  2. It doesn't hurt to make one last final check of everything before removing the string and going for a ride on your perfectly aligned Triumph motor bike.
650 Triumph