Auto lifting points

[lemmy999]

I have a simple question that is probably a stupid question, but here goes. I have read that the center of gravity for a FWD vehicle is usually in front of the front seat (so well forward of the mid point between the lifting points). Also the lifting points (pinch welds) for many vehicles are located just behind the front wheel and just in front of the rear wheel. For a symmetric lift should the automobile be positioned such that the post and arms are as shown in the top of the picture (lift arms are swung out at the same angle and are the same length and the post is lined up with the mid point between the lifting points) or as shown in the bottom picture (the middle of the post lines up with the center of gravity)?

Thanks.

 

[olytdi]

On my TDI Golf, the lift points differ from the jack points on the pinch weld. As such, that math has already been done so you center the pillar between those front/rear lift points. This does result in it being more along the lines of the bottom image to account for the nose heavy front-wheel drive and heavier diesel engine.

On my Gen 1 Trooper, you can put the lift points anywhere along the truck frame. As such, I have figured out where to offset those such that the vehicle is balanced and not nose-heavy. If I put the arms equally between the wheels, the load is unbalanced in favor of the engine side.

I find both vehicles are greatly nose heavy. I ALWAYS use front/rear tall jack stands to lock in the vehicle once it's up in the air. That makes things rock solid and provides for an extra margin of safety.

 

[firebirdparts]

You don't have a choice with a symmetric lift. It doesn't have enough adjustability to get the posts to the CG on a front wheel drive car, and probably some rear drive cars. My opinion.

Lining up the CG with the posts will certainly reduce the friction on the carriage when it move, but ultimately it's made to take it.

 

[lemmy999]

Thanks. I lifted my car tonight on the lift and it worked great. I lined it up more like the top of the drawing and it was very stable and lifted and lowered without any issues.

 

[Fluelikesymptoms]

I was wondering why in the world someone would make a thread asking this.

Then I realized I would do something like that.

And then I also realized your the same guy who got his truck stuck on his brand new lift last week, suddenly the world made sense agian.

In my experience the decision of where the posts are on relation to the CG of the vehicle is not going to be up to you, but up to the lift arms themselves. Often times you dont have the adjustability of the arms in your favor and you have to get it the best you can, often times meaning more center of the car because the front arms just aren't short enough to make a good contact with the lift points.

Some trucks the arms just aren't long enough, on my 99 Silverado I have to lift the truck using underneath the leaf spring bushing as a lift point. Kind of sketchy but also the safest place, any optimal points along the frame is too far up the body and leaves the rear end tilted.

I once had to lift a vehicle where the lift point was designed to be use with the actual arm itself and not the adapter. I cannot for the life of me remember what it was and no amount of googling seems to jog my memory. I think either a bmw or Mercedes, I want to say it was a high end german vehicle, I remember being very put off and concerned about damaging the vehicles side skirt but it was actually more stable than most lift points on other vehicles.

Anyways point is, usually the lift is going to tell you where. Obviously you will be able to tell when you go to set the arms if you should and can move the car back for a more stable lift. I mean if the car is pulled way forward and you think to yourself "I can probably pull this car back a foot and lift it" then you should probably do so.

Another thing that is going to give you the best opportunity to get as close to CG as possible is making sure you pull the vehicle in between the posts evenly.

If you pull your car/truck and you have 1 inch between the left post and the left side of the vehicle, but you have 7 inches on the right, your going to have a difficult time getting to center gravity as the left side arm will be too long for its lift point and the right side will line right up.

In the end it's pretty much going to come down to what you have to work with and some common sense. I suspect you'll be fine

 

[Fluelikesymptoms]

Another thing I want to add that I dont ever see mentioned that I wont speak too much on due to disclosure agreements. My experience in manufacturing is that many manufacturers actually have multiple lift points designed throughout the vehicle to support changes in the way the vehicle gets carried throughout the plant for various processes.

I wouldn't go experiment some of these points are only used when the vehicles isnt as loaded down with weight such as getting painted.

Point is if your careful and use common sense you shouldn't have too many problems, but dont take that as in it's okay to take risks sometimes avoidable user errors happen and it can been catastrophic or even fatal.