Axle Spikes, Pivot Plugs, and Chains

Unfortunately, Yamaha left huge holes in the ends of the swing-arm pivots and the axles. Try as I might, I just didn't feel confident estimating the precise center of each hole. I firmly held my tape-measure's position, then estimated the center of the corresponding hole. However, I knew it was way too easy for me to be off by as much as 1/16 inch -- maybe more.

The most common solutions to getting better measurement results are as follows:

• Simple, axle/pivot inserts
• Axle/pivot inserts with integrated measuring
• Trammel Points

Simple, Axle/Pivot Inserts

The purpose of these is simply to eliminate the guess work of finding the center of the large axle and pivot holes. That's all they do, but they can improve accuracy and consistency, if done well. They are quick and easy to make -- another plus. They do not, however, eliminate the need for two, steady hands to measure the pivot-to-axle distances.

To create a set of these inserts, an online buddy, Jack (Ripper115 on the Delphi Road Star forums) suggests the following:

Use four 5/16" x 1" bolts. Mark the center of each bolt by scribing an 'X' across bolt-head points, and then smack the center with a sharp punch.

Next, wrap the threads of each bolt with just enough masking tape or electrical tape so that each one snugly fits into one of the four measurement holes (each side of the swing-arm pivot, and each side of the rear axle).

This completes the set. To use them, just insert each bolt into its appropriate hole, and use the center punch mark as your precise center marker.

I would offer the following suggestions:

1. Chuck the bolt shafts into a drill, drill-press, or machine lathe. Then file the spinning head-top a little bit, so as to create concentric circle marks. Then use the circle/spiral marks to locate the bolt's precise center. See photos above and below.
2. If you don't feel confident using a center punch with great accuracy, you could use a light touch with a permanent marker or touch-up paint-pen instead.

Axle/pivot inserts with integrated measuring

This is a 'next step up' from the simple inserts described above. It's more complicated to make, but eliminates the need to hold a measuring tape (or other marker).

Basically, I made four nipples that could be inserted into the pivot/axle holes, and integrated some small chain to act as my measuring-stick. The two nipples for the axle holes had cone shaped ends so as to make it easy to locate their centers. Note: Construction dimensions are given in diagrams later on this page.

Then I attached a long segment of ceiling-fan pull chain to the two swing-arm nipples. See photo below.

Then I inserted one of the chain-nipples into the swing-arm pivot, and inserted the cone-nipple for the same side of the bike into the axle hole. I stretched the chain back past the cone-nipple. Then I located a link right near the cone's point, and wrapped a tiny piece of phone-wire at that link. See photos below.

Finally, I removed the chain-nipple from the bike, held both chain-nipples precisely side-by-side with their chains dangling, located the link with the phone-wire on the one chain, and then wrapped a tiny piece of phone-wire around the corresponding link on the other chain, too.

Note: As an alternative to using phone wire, you could use a permanent marker or paint-pen.

Now all I had to do was stretch the chains back to the axle nipples, and compare chain lengths. See photo below.

To create the nipples for this method, I used my drill press and a file. Their dimensions are as follows (also see diagram drawings below):

• All nipples started as 1/2" aluminum rod
• Swing-Arm Pivot nipples are 2.5" long
• Axle Pivots are 2" long
• Left Swing-Arm Pivot --
  • Outermost 1" = 1/2" diameter.
  • Drill a 1/8" (0.125") lateral hole, 0.6" from the outermost end.
  • Then the next 1" = 0.39" diameter.
  • Then innermost 1/2" = 0.365" diameter.
• Left Axle --
  • Outermost 1/2" = 1/2" diameter.
  • Outermost 0.3" tapered to cone.
  • Next 0.1" = 0.35" (channel cut as a convenience to lay chain on)
  • Innermost 1.5" = 0.48" (with an invisible taper into the 1/2" diameter for a snug fit)
• Right Swing-Arm Pivot --
  • Outermost 1" = 1/2" diameter.
  • Drill a 1/8" (0.125") lateral hole, 0.6" from the outermost end.
  • Then innermost 1.5" = 0.53" diameter (accomplished using electric tape wrapping).
• Right Axle --
  • Outermost 1/2" = 1/2" diameter.
  • Outermost 0.3" tapered to cone.
  • Next 0.1" = 0.35" (channel cut as a convenience to lay chain on)
  • Innermost 1.5" = 0.34" (with an invisible taper into the 1/2" diameter for a snug fit)

This is quick and easy to use, and the chain is fairly accurate. But to my surprise, the chain has a bit of stretchiness to it. Not much, and it's not hard to give a consistent stretch factor. But I was hoping to eliminate this factor altogether. Also, it isn't as easy to detect tiny alignment adjustments as I would have liked.

On the other hand it is FAR superior to eyeballing a tape measure to the pivot/axle centers.

In the end, I went ahead and fabricated a pair of my own Trammel Points. See description below.

Trammel Points

I initially got this idea from another online buddy, Marty (BCHermit on the Delphi forums), but others have recommended it, as well. Below, is what Marty posted about this tool:

"Here is a pic. (See above) They slide onto an aluminum bar or wooden shaft of the required length. They are used for measuring center points on axle and swing arm bolts. Ace Hardware has them for about $24.00." - Marty, BCHermit

I couldn't find Trammel Points at any big-box hardware stores locally, so I decided to just make my own.

It took about four hours for me to make. My work pace was slow and steady, but the results were good.

I cut off two, 2" pieces from a 1/2", solid aluminum rod. I chucked each piece (a.k.a. each nipple) into my drill press, and used a file to create blunt, cone ends on them.

Next, I drilled a 5/32" hole in the side of them to hold a long, 1/8", steel rod. The holes must be located at identical distances from the ends of the cones.

Tip: If I ever decide to do this project over, I would change the following:

• Use a slightly larger diameter steel rod, to increase stiffness.
• Drill the holes closer to the cone-ends, to reduce the effect of any rod-to-nipple misalignment. I would make the holes around 1/2" from the end of the cone.
• Make the nipples 1/2", or so, shorter, so as to reduce the depth needed for threading (see below for details on this).

Note: It is best if the holes are directly through the full diameter of the nipples. It is important that the holes be drilled precisely square (perpendicular) to the nipples. It is most important that the steel rod be straight and true. Deviation from this will defeat any hope of alignment accuracy.

I smeared glue on the end of the steel rod, and slid one of my nipples on. Then I let it set over night. I used JB Weld, but any strong glue, suitable for metal-to-metal bonds, will work fine. See photo below.

Tip: Be sure you allow the steel rod to sit squarely within the nipple while the glue dries. Otherwise alignment readings may not be accurate.

To accomplish this, I just suspended the rod horizontally, put glue on the end of the rod (and into the nipple's hole), slid the nipple onto the steel rod, and wiped off any excess glue. That way, gravity assured me that the dangling nipple would dry squarely on the rod.

Then I drilled a blind hole down into the blunt end of my other nipple. The depth of this hole must be a little deeper than the side-hole. I then tapped the blind hole for a set-screw. See photo below.

To use this gadget/tool, all I have to do is insert the points into the axle and swing arm holes, and tighten down the set-screw. This quickly creates the length reading of my first side. Then I just walk over to the other side and attempt to insert the nipple points into the holes. If the nipples don’t perfectly match, I know I’ll have to adjust the axle. See photos below.

Note: The glued nipple is wrapped with electrical tape because the right-side swing-arm hole is slightly bigger than 1/2" diameter, and my aluminum rod was only 1/2".

Measurements and adjustments continue until I my points precisely rest into the centers of the axle and pivot holes on BOTH sides.