J Bar Frame Mount

[7uptruckracer]

When you see people talk about 8 1/4, 9 1/4 and so on hole on the frame mount where are they getting that measurement from

[andy16]

from j bar bolt on frame to ground subtract j bar bolt on pinion to ground sometimes and sometimes is from the bottom of the 2x2 square tube to j bar bolt. they usually both are close to each other although not the same. the subtraction method i use for comparing different chassis makes. if they are the same chasis just measure from bottom of 2x2 imho

[7uptruckracer]

Anyone else care to chime in? How does rocket determine which one is which?

[rocketdent]

Measure from bottom of the 2x2 sq tubin to the center of the bolt going thru the jbar.

[Matt49]

I have always measured from the bottom of the frame rail, not the bottom of the vertical 2x2 that the slider attaches to. But maybe when you guys are saying 2x2 you mean the frame rail (if it's a square tube car). But I can see where one might get confused and think that you meant bottom of the vertical 2x2.
MasterSbilts are measured from the bottom of the frame rail.

[dfhotlm33c]

Let's be clear. If you want to know the amount of actual rake in the j-bar, you need to follow the procedure listed where you measure the distance from the center of the mounting bolt on the frame to the ground, and then measure the distance from the center of the bolt on the pinion to the ground. Subtract these two measurements, and you will obtain the amount of rake.

However, chassis manufacturers list the starting points for j-bar frame height: this is a dimension that is usually measured from the bottom of the frame rail to the center of the bolt.

Hope that clarifies!

[andy16]

the bottom of my 2x2 is equal to bottom of frame on my car im pretty sure? rocket bfe cant confirm till later but pretty sure.

[rocketdent]

Same for my mastersbilts and rockets. The 2x2 vertical bar j bar connects to chassis is flush w bottom of frame rail. Call ur manufacturer if yours is diff and ask what should be and where to measure.

[Matt49]

Interesting. On our MasterSbilt the vertical 2x2 sits on top of the frame rail right where it ends. It's an 1-3/4' car though so that could make a difference. I guess I haven't paid close enough attention to the 2" cars I've messed with.

[7uptruckracer]

Thanks guys I found it in the book I had I was looking right at it just didn't see it for looking. I was from the rail to the mounting bolt!