Lowest Leaf Sprung Wrangler

BenE said:

Listen to what you are saying. If the drive train stays in the same spot, and you lower everything else down (frame, body, cage, and all that heavy stuff), you are trying to convince me that the COG is somehow going to rise???
If you lower the weight (the weight is closer to the ground), you lower the COG, period.

I understand why you cant lower your rig any more (same reasons for all of us), but understand, if you did, you would also lower your COG.

I know you are a teacher, and probably way smarter than me, but what you are saying doesn’t make sense (at least not to my feeble brain).

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I agree with this ^^ completely.

Here is an approximation using some numbers that I think are fairly good representations of a lot of rigs (especially full body rigs NOT buggies)

Motor + Tranny + T-case = 450 + 175 + 100 = 725

Assume a rig with roll cage weighs about 3500 lb trail ready with a cage spare tire tools etc.

Disregard the weight of the axles and tires say 1250 lb (they are not moving for purposes of this discussion)

so... rig weight - axles and tires - drive train = body frame interior cage etc.
3500 -1250 -725 = 1525 lb

So you move the drive train 725 lb up 2" into the body and frame and then lower the body and frame and drive train or 1525lb +725 lb down 2". This means that you still move 1525(down)+725(back down)-725(up) =1525 lb down two inches and effectively lower your center of gravity.

Say you raised your drive train up 4" and then dropped the body and frame 2" that would mean that 725 lb was still 2" above its original position and 1525lb went down 2" from its original position. So you still lowered your moved a total of 1525(down)-725(up) = 800 lb down 2" and effectively lower your center of gravity.

It all depends on what the components that make up your rig weigh.

MuddyPaws said:

I can't find the right words to explain it. I am not claiming to be smarter than anyone though. But going on rough "total mass" numbers is just wrong. You might be moving the whole 1525 down 2 inches, but where is the COG in that 1525? Is a large chunk of it high from the cage, seats, top and tools? Might be, depends on the rig Then you move that 750 from the drivetrain into that zone and it "may"...."could"....negatively alter COG.

Like others have said....it really depends on the rig and the components.

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I won't claim to be smarter than anyone either. I learn something new every day!

What you said is very important.

Its a little more complicated than this but...
The center of gravity or center of mass of an object is basically the average location of its mass. This can be loosely translated to the CG will be near the heaviest portion of an object.

And so, its a little more complicated than this but...
The center of gravity of a jeep (or any object) will be the average location of the centers of gravity of its components.

So as we said it depends on the rig and its components but...

Unless someone is packing fat chicks on top of their roll cage or bricks in their frame the CG of a body, frame, roll cage will likely be somewhere below the dash or near the firewall of the tub.

And the CG of a drive train will likely be around the center of the transmission bell housing.

Average the two and you will have a CG that is generally estimated to be near the top of the transmission bell housing

Because your body, frame, and cage is heavier moving it 2" will have a greater effect on CG than moving you drive train 2".

The distance an object is moved will also change its affect on CG. So you don't want to raise the drive train any more than you have to because moving a light object a great distance could have the same effect on CG as moving a heavy object a small distance.

So as long as the body, frame, and roll cage significantly out weigh the drive train and the builder lowers the body, frame, roll cage, and drive train after raising the initial raising of the drive train the rigs center of gravity should still be lower. Unless the drive train was moved up far greater than the body, frame, and roll cages moves down.