Please check my math on Jack limits

[1930artdeco]

I just got a Weaver WA-72 floor jack rated at 2 tons. I am going to use it to jack up my 88 F150 at some point to change shocks, brakes etc.

So it is rated at 2tons (4000lbs.) and the truck weighs in at around 5000 lbs. if I lift just the back half up to swap shocks I am only lift 2500 lbs. correct? I just don’t want to get close to the 2 ton limit. Is my math correct?

Mike

 

[CGarage]

That is correct, likely less weight actually. But to be safe, use quality jack stands rated appropriately to support the vehicle in addition to the jack.

 

[1930artdeco]

Always!!!!! Good to know I can still add-more or less.

 

[drmarkr]

The center of gravity on the truck is not centered at the middle of the axles....it's more to the front (engine/etc), so you're lifting less than 2500 on just the rear. Conversely, the front will be more than 2500, but not likely to exceed 4000. You could weigh all four wheels and then calculate the center of gravity, but for what you're doing here, not necessary, IMO. If the jack won't lift the front, then borrow/buy (Garage Journal way!) a bigger jack.

 

[Beerhippie]

If it takes all your body weight on the handle to lift the truck, you've found the limit. If oil suddenly shoots out of the jack, you've exceeded it.

 

[rooster59]

I would just do 1 wheel at a time. Trans in park, parking brake on if you can, chock the wheels. Use jackstand(s).

 

[OccupantRJ]

If it takes all your body weight on the handle to lift the truck, you've found the limit. If oil suddenly shoots out of the jack, you've exceeded it.

Does that mean that the jack climaxed?

 

[CGarage]

Wheels need to be chocked.
The 2 ton jacks are a lot more maneuverable than the 2.5 / 3.0 ton and weigh less, which is an advantage.

 

[yatg]

Does that mean that the jack climaxed?

prematurely

 

[ajchien]

FWIW, the weaver WA72 has a built in safety overload valve. The jack will know when you have exceeded 2 tons, and refuse to lift anything higher than 2 tons.

Do you see the spring at the pressure release valve mechanism? That spring is calibrated to resist the equivalent of 2 tons. If you exceed 2 tons, then that release valve will automatically open preventing any damage to the jack.

That said, the spring was calibrated to 2 tons from the factory. There are a few jam nuts that adjust the tension of the spring. If someone has messed with the spring/jam nuts, it could be out of calibration.

see this linked diagram. part s-2591 is the spring: https://media.hcrcnow.com/uploads/drawings/weaverwa72.pdf

 

[RoninB4]

But to be safe, use quality jack stands rated appropriately to support the vehicle in addition to the jack.

+1 on using better quality jack stands. Those stamped steel jack stands rely on the welds to hold them together, some have been known to fail. This is especially relevant if you're going to be underneath the vehicle. Be safe, live to tell the tale.

 

[1930artdeco]

My jack stands are the stamped steel kind but they are old-as in made in Los Angeles, U.S.A. or just plain USA. Not sure about the cast ones as I have seen them crumble under weight.

Mike