In this example, we have mounted the rear wheel in the frame, and used a frame jack to set the “Attitude” of the frame stance. This step is important, as changes to the angle of the lower tubes to the ground can change the neck height, and neck angle as the frame pitches upward.

We typically use a Digital Inclinometer to establish the neck angle for our calculations to measure the angle within one tenth of a degree. We do not expect everyone to have one of these, and we’ll show you a few other ways to get the neck angle pretty accurately with common tools

To accurately measure the neck angle relative to the table, we need to zero the device. In Photo 1 above, you can see that we have used a long straightedge set on top of the table surface to average the table surface. This is important because these lift tables are NOT flat, and we need to establish a flat average surface plane to measure from.

 Photo 2 below illustrates the error we will correct out by zeroing the gauge.

As you can see, there’s a little error here. Our floor is pretty flat here as well. Most garage floors at home slope toward the door, and can induce more error. If you are using a lift in your garage, try to set the table across the natural slope of the floor to eliminate that possibility. Most garage floors are pretty flat side to side.

By re-setting zero on the gauge, we get a relative zero measurement as you can see in Photo 3 below:

After the gauge is set, simply set the gauge across the top of the neck as shown in Photo 4 below:

The Neck angle on this frame for purposes of building a front end is 33.7 degrees.

Keep in mind that:

1.The better these measurements are, the more accurately the front end can be built.

2. There are other ways to do this, but this is how we do it.

3. The smaller the neck angle, the less effect small errors have on the length of the fork

OK. Let’s take a look at other ways to measure the angle. A Machinist Protractor is very inexpensive, and can be used as shown in Photo 5:

Keep in mind here that as we use a level to determine the angle, you must use the same technique on the table to subtract (or add) the correction angle into the measurement for a relative angle.

Another tool to use like this is available at lots of tool stores, and is pretty easy on the wallet. We see it in use in Photo 6 below:

Now that we have the neck angle, we need to know how far from the ground the neck bearing is.

 We call this measurement Lower Neck Bearing Height.

Measure from the centerline of the lower neck bearing race (Bearing IN PLACE) directly to the table as shown in Photo 7:

It’s important to measure the lower edge of the bearing in the race, along the centerline of the neck axis, as shown in Photo 8.

This one measures 32 and 3/8” from the table surface. Try to get within 1/16” here.

This allows us to calculate the length of the fork, as long as we know the tire size, type and brand you will be using. We have a table of “loaded” radius dimensions for most major tire types we can use to determine the distance from the table to the front axle.

With this information, we will build you a springer to fit in the space required, and  we will pre-load the springer so that it will settle to this height when it is fully loaded with the bike weight and average rider.