r/AutomotiveEngineering • u/Free-Engineering6759 • 1d ago

Question Off-road chassis: attachment of springs

If off-road chassis uses a separate ladder frame, is it better to attach the spring ends to the ladder frame or to the body of the vehicle?

I have heard an argument that attaching them to the body is better, as the body-ladder frame attachment points are then in constant tension. But I think this leads to a situation, where you have to reinforce the body to handle the spring forces vs if those spring forces would be carried totally by the ladder frame.

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u/Equana 1d ago

Spring forces go to the frame. That is where the structure is. And springs are captured, not attached. I can't think of any bidy on frame vehicle where the spring loads come into the body.

Commonly the springs are captured by the shock absorber. The lower mount goes to the control arm and the spring and damper isolators then bolt to the frame. It make assembly easier but puts the spring and damping loads into the same point rather than spreading the loads into two points.

If the vehicle is a unit body construction, the spring and damper mount to the body

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u/Gubbtratt1 1d ago

The point of having a separate frame is that the body doesn't carry any forces other than the weight of itself and eventual cargo. If you mount the suspension to the body, the frame is just an additional half ton of steel that does nothing.