Wheel Timing

Good wheel timing is important to consistent shooting. Have you ever pulled back a cam bow expecting to find a hard wall and discovered that the bow felt mushy at full draw? This problem is usually associated with wheel timing. Its not uncommon to receive a brand new bow with wheels that are out of time. It is up to you to properly adjust the wheel timing and tiller of your bow. Poor wheel timing can also make it difficult to stay on the spot when aiming.

Quick & Dirty Wheel Timing

You can do a fair job of wheel timing with no special tools as follows:

	Slowly draw the bow back while watching the bus cables and cams.
	When you pull through the valley into the wall, one bus cable will come to rest on the back side of the cam before the other cable.
	If the Back Side of the Top Cam touches the bus cable first, you will need to shorten the bus cable connected to the bottom limb by adding twists to the bus cable.
	If the Back Side of the Bottom Cam touches the bus cable first, you will need to shorten the bus cable connected to the top limb by adding twists to the bus cable.
	Do not adjust cable lengths by more than one or two turns at a time. You will be surprised at how quickly the wheel timing will change.
	When you have the wheel timing close, make your adjustments by twisting the bus cable in 1/2 turn increments.
	Note that shortening bus cables will slightly increase the draw length of the bow. If the draw length is getting to long, adjust wheel timing by untwisting the opposite bus cable described above.
	It was necessary to shorten the bus cable connected to the bottom limb by 5 1/2 turns to bring these wheels into alignment.

Note how the bus cable is in contact with the back side of the top cam in the photo below.

Note how the bus cable is well away from the back side of the bottom cam in the photo below.

Figure 1

Figure 2

Precision Wheel Timing

The following technique provides detailed instructions for obtaining perfect wheel timing on two-wheel compounds. You will require the following tools to perform these adjustments.

Bow Square

Narrow Straight Edge

Ruler or Calipers

Bow Jig, to pull bow back for measurements.

Bow Press, to take tension off of bus cables for adjustment.

Adjust wheel timing as follows:

Remove cable guard slider from bus cables.

Place Bow on Bow Jig and draw the bow back until one of the bus cables comes in contact with the back side of a cam (see Figure 1 above). Note, it is important that you draw the bow back pulling from the same location as you would if you were shooting the bow. You may need to draw with an arrow on the string to draw from the correct position on your serving. I tie nocking points above and below the nock which allows me to time the wheels with no arrow on the string.

Place a bow square on the bus cable as it exits the cam as shown in Figure 3. Use a pair of calipers or ruler to meaure the distance from the axle to the bow square. It is very important that the bow square be placed the same distance from the top axle as the bottom axle when making your timing measurments. As shown in the figure, I chose a distance of 1.5" away from the axle as my reference point.