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Why Chain Alignment Matters

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  • Why Chain Alignment Matters

    Why does rear wheel alignment matter and how sensitive is it?

    I changed my chain recently and aligned the rear wheel by measuring the adjustment bolt and other reference points. I also eye-balled the chain.

    I have seen various alignment tools, laser, alignment bar etc. I am wondering if that level of precision is necessary and why?

    Perfectly aligned chain pulls more efficiently
    Perfectly aligned chain wears better
    Perfectly aligned wheel tracks and wears better


    Miss-alignment might pop clip master link?

    Is perfect necessary? How good is good enough?

  • #2
    If the rear wheel is not aligned with the chassis there will always be some side push being delivered to the bike. It may be minor, but it will still always need steering compensation. How good is good enough? Does the bike track straight?

    The most accurate way to check alignment is to measure from the swingarm pivot's center to the axle's center. On many bikes however, there's no easy way to do this. Second best is to measure from the swingarm pivot's center to the markings that are stamped or engraved on the swingarm. Do this to verify the location of the markings. Sometimes one side's markings are a little bit forward or aft of the other. Once you have determined the difference (if any) between the two sides the markings become usable.

    There are other, usually more complex, ways to measure, but they usually begin to depend on more and more parts being square and properly adjusted.

    When you are setting the alignment, and chain tension, don't back off of your adjustment. It's best if everything is under tension when you reach the correct setting. Start a little loose and draw the axle rearward. When it reaches the correct spot for chain tension, lock the axle down.


    • #3
      My bike has adjust markings only on one side and they are a sticker.

      The adjuster nut is behind that axel rather than in front of it. It stops the axle from moving forward. When I get it adjusted where I want it, I am pushing the wheel forward to keep it where I want. I push my thigh against the rear tire to push it forward from behind the bike while I am locking down the axle.

      As far as I can tell the bike tracks straight. But I have not ridden it much since I changed the chain and did the alignment. It runs and shifts noticeably better than it did before the chain change.


      • #4
        Critical. Use a long string to check it. With the bike totally vertical, One wrap around the rear part of the rear tire, draw both ends of the string forward so the just barely touch the front part of the rear tire, your front wheel should sit right between the strings.

        but is sounds like you have it right.


        • #5
          View this 1 minute in:


          • #6
            Get real good at it and you can do motorcycle wheel alignment checks for all your friends at 100 bucks an hour, just don't show them how easy it is


            • #7
              First try I am off by about 5 mm. But I need to refine my technique a bit. Not sure my first attempt is accurate.

              Going to make a perfectly sized wooden dowel for the front and use braided fishing line to get a more precise measurement.

              But I think I am pretty close.


              • #8
                Working in metric I see too I'm impressed


                • #9
                  It is a metric bike. The tires are metric 160 mm. Just going with the flow.


                  • #10
                    I am going to make a dowel with slots (or maybe holes) 16 cm apart (width of rear tire). Wrap braided fishing line (or maybe fine shock cord to keep it snug) around the rear tire and run it forward to the slots. Run it through the slots then wrap it tight and jam it under the front tire. This will cause the line to be downward sloping but it does not seem that should matter. Center the dowel on the front tire and then adjust the rear tire until it is perfectly aligned with string.

                    Then make a youtube video, sell adds and just wait for the millions to roll in.

                    And of course, I will sell my handy dandy alignment tool patent to a tool manufacturer. More millions for sure.

                    Why would I want to make a measly $100 per hour to do actual work when I can make millions for doing nothing?

                    Copyright, all rights reserved 2020.


                    • #11
                      2 Laser beams should work.


                      • #12
                        I’ve used string, flourescent bulbs, rubber bands tied together, bar stock, all to get the rear wheel as close as possible, to the longitudinal axis.
                        Even need to inspect the rear tire carcass for imperfections when doing this procedure.
                        Knowledge speaks, wisdom listens.


                        • #13
                          2 steel rulers, yes, you need to do it on more then one section of the rear tire, if the tire spins wobbly we have yet another problem. lol go for your average wobble alignment, fix your tire or adjust your spokes.


                          • #14
                            Front tire is 120 mm, rear 160 mm. Perfect would be 20 mm space on each side. I am getting 16 mm on the left and 21 mm on the right. 5 mm difference plus or minus some slop since the total does not equal 40 mm. Tire imperfections, inflation, rear tire is elevated and unweighted, front tire is weighted and my process is not perfect yet.

                            So that would mean that the right side of the axle needs to come forward just a bit. But I am also thinking my measurement error is probably a couple mm so I am thinking it is not too bad as is.


                            • #15
                              Everything has an allowable tolerance you'll be the first to notice it when you ride it, that's the cool part about working on your own bike

                              I have one I am thinking about trading in now because I am growing a little intolerant of it.
                              I did something silly, I bought 2 near identical motorcycles except one has more power then the other guess which one I like.