One Man String Alignment

Several of the cycle rags have printed a procedure for “string alignment” to more precisely align the rear wheel to the front, since the OEM adjusting marks on the swing arm are notorious for their inaccuracy. Their procedure requires 2 people. This procedure takes one person, is more precise and it’s easier to boot! Here's how:

 

  1. It’s suggested you do this in a well lit garage. Set your bike on rear wheel stands. Center the front wheel. Put the bike in neutral.
  2. Loosen the rear axle nut so that the eccentrics can turn independent of each other. Loosen the eccentric clamp bolts on both sides, slack the chain, then tighten the eccentric clamp bolt on the left side.
  3. Make a plum bob using any convenient weight and a piece of string. Hang it so the top edge touches the “top” of the front tire (missing the axle, brake disc, etc.) and note if it doesn’t touch the “bottom” edge of the tire or is hard against it. When the bike is sitting vertical, the string should just kiss the bottom edge. Shim the axle stand as necessary so that the centered front wheel is vertical and the bottom string gap is 1/16” or less.
  4. Cut a piece of string about 20’ long. Loop it around the front tire low enough so that it misses the bottom of the engine, brake discs, etc. when pull the ends back to the rear tire and let them lie for now.
  5. Rotate the rear tire so that a spoke is at about the 7 o’clock position viewed from the right side of the bike. Put the transmission in gear. Loop one end of the string around the back of the rear tire tread and then over the spoke. Tie a convenient weight, such as a nut or washer to the end and let it hang (this keeps tension in the string). Do the same to the other end of the string on the opposite side. You should now have two strings running along each both right and left sides of the tires, front to rear.
  6. Adjust the string loops up or down at the front and rear tires as necessary so that they touch only the edges of the tires, as high up on the tires as possible and at the same height measured from the floor to the string, within 1/16”.
  7. Cut a plastic soda straw approximately 1/4” to 1/2” wider then the rear tire. Notch the ends of the straw and slip the straw between the two strings so that it’s supported by them. Slid it back until it’s about 1/2” from the rear tire.
  8. There should be a gap between the back edge of the front tire and the string on each side. Using a pocket scale or ruler, measure the gap on each side and turn the front wheel so the gap is the same on both sides within 1/16”.
  9. Go to the rear of the bike and sight down the string on one side and then the other. Note the gaps between the string and the front edges of the rear tire. Carefully and gently rotate the free eccentric to make the gap on each side equal.
  10. Check the front tire gap as in step #7. If adjustment is necessary, repeat step #7, then repeat step #8.
  11. When the front gaps and the back gaps are equal within 1/16”, carefully tighten the right eccentric clamp bolt, then torque the axle nut. (Once the axle nut is tight the eccentrics will turn together.)
  12. Loosen both eccentric clamp bolts and adjust the chain for specified sag. Note the difference in the left and right swing arm marks with the tires aligned correctly and write it down. If you ever loosen the rear axle nut, as when changing a tire, you can re-establish alignment by offsetting the alignment marks the noted amount.

Don’t be surprised if the alignment marks on the swing arm are off quite a bit after you do this alignment. Enjoy the fact that your bike will now track straight down the road and rear tire wear due to misalignment will have been eliminated.