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Tech Made Simple: The J-Bar

Billy Moyer Jr.

Billy Moyer Jr.

The J-Bar Explained

By Billy Moyer Jr.

We are going to talk about the J-bar on a race car today. It is sometimes called the pan-hard bar and is located on the rear of the racecar.

It hooks to the left side of the frame and goes across in the shape of a “J,” which is what gives the part its name. The other side of the J-bar hooks connects to the car, adjacent to the drive shaft (pinion side).

We have different options when it comes to a pan-hard bar such as the straight bar, bud bar (also known as the Rayburn bar), and the most popular is the J-bar. We use the J-bar to keep the rear-end of the car in the desired position. The placement of the J-bar controls several settings on the rear of the car.

J-Bar

With it we are able to set the side-to-side measurement, which allows us to define the placement of the rear-end from one side or the other. The placement of the rear-end directly affects how and where your shocks and 4-bar rods are attached. As you can already see the J-bar can have a major impact on how well or how poorly the car handles.

The J-bar can vary in length from roughly 18 – 22 inches from center to center. We have numerous adjustments on our race car, and moving the J-bar left to right can really change the handling characteristics.

Moving the J-bar to the left side of the car tends to make the car tighter, which creates more traction. Conversely if you pushed the bar to the right it would result in or freer or looser handling car.

A longer – 22 inch – bar tends to stick the car harder in the corners. You have to be careful because this can also create a “push” in certain conditions. A shorter J-bar makes the car react a little quicker, but tends to make the car looser. I usually run a long BSB Manufacturing J-bar on my Billy Moyer Victory Race Car. I like the feel of the car sticking harder on entry and try to adjust the car elsewhere if I am stuck too hard or if the car is too tight.

You can adjust the J-bar with the measurement on the frame side or the pinion side. However, it’s just important to be consistent on how you are documenting it. Otherwise your notes might not always match, and you could be in for a big surprise the next time you hit the track.

The higher the measurement from the frame side tends to stick the car harder and make it tighter in the corners. The lower the measurement would make the car turn in easier and have less stick.

You can lower the J-bar on the pinion side in order to tighten the car on corner exit, which gives the car more traction

J-Bar 2
Example
Too tight

If I am at a track like Tri City Speedway (Pontoon Beach, Illinois) – which is known for being a “tight in” type of racetrack – I would take a look at my J-bar placement on the frame if I was too tight getting in the corner. I would lower the J-bar on the frame with hopes of it making my corner entry freer, which would allow me to carry more speed into the corner.

Too loose
If I am at a track like Belle-Clair Speedway (Belleville, Illinois) – which is known for being a “looser” type of race track – I would think about dropping my J-bar on the pinion. It is a very low speed track, and you need all the scotch you can get. If I drop it on the pinion, it would tend to give me more scotch and allow more traction since I am stuck harder in the center of the corner and on exit.

A standard setting for most J-bars would be 8-9 inches from the bottom of the frame to the center of the J-bar heim. The standard setting on the J-bar would be the center of the pinion.

Hopefully this article gives you some insight on exactly what a J-bar is and its function on a race car.


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