MBMB

I'm shopping for a two-post lift (an Ammco B2900), and I found one used for a decent price. In trying to lay it out on paper, however, I've calculated that the arms are too long to fit under the jack points. Does that make sense?

How can I jack up my 928 if the pads on the lift don't reach the jack points?

Should I be looking for a lift with shorter arms?

TopDownL79

Shouldn't either the pads or arms adjust? I can't recall seeing any two post lifts that didn't have some kind of adjustability built in...

If not, it should be pretty easy to make some sliding mounts for the lift pads.
Assuming, of course, that the price is right!

atb

Our Autolifter two post has telescoping arms. Even so the 928 really has to be correctly positioned to hit all the pads. If each arm were about 6" shorter it sure make like it alot easier. As it is now, when the pads are lined up with the lift points, it's very difficult to get the doors open. Good argument for getting the assymetrics.

Garth S

Most lifts can accommodate cars & trucks both larger and smaller than the 928. I've no clear idea of the swing angles allowed by the Ammco asymmetric lift; however, for my lift, I centered the rectangle of the 4 lift point centers of the car on the 'drive on' centerline of the lift. This rectangle is 52.5"W x 54"L. From that, it is pretty easy to graph the swing angle and mim/max reach of the front short asymmetric arms from their pivot points. I would hope that that would allow many points of contact with the lift pads on the car.
Once there is a satisfactory match here, force the rear arms to contact the car.
That's the process, but somewhat worthless without dimensions ...

MBMB

Here are the dimensions I know:
109" wide between lift posts;
52.5" wide between jack points on the car;
So 28.25" wide between jack points and post.
Lift arm pivots are 4" inside lift posts, and 18" apart.
So 24.25" wide between lift arm pivots and jack points.
Lift arms are 27-41" (front) and 38-59" (back).
54" long between jack points.
So, drawing a parallelogram, the two parallel sides are 24.25" apart and are 18" (lift side) and 54" (car side) long.
One of the non-parallel sides is 27" (the minimum length of the front lift arm);
By my math, the other non-parallel side is 34.2", which is less than the back lift arm's minimum 38" length.

I haven't seen the lift set up, so some of my assumptions may be incorrect. I don't see how I could be 3.8" off, though.

Garth S

As an asymmetric lift, is it correct to assume that the front arm swings backwards beyond the line connecting the two post centers? If so, with the front arm at 27" and swung back at ~15 deg, all four lift points will be met when the rear arm is ~ 46" extended.
If the front is extended to 34" and swept back at an ~40 deg angle, the rear arm will just extend to reach the car at ~57" .... 2" shy of its max travel.
It is best to shorten the front arm to center the weight between the two posts.

Anyway, provided the front arm is free to swing behind the post to post centerline, it looks good to me. Too many numbers on the back of a dirty envelope ... time for a drink!

Jim bailey - 928 International

Think Trapezoid usually the front arms go forward rear arms to the rear

MBMB

I meant "trapezoid" instead of parallelogram.

Seventh grade geometry was a long, long time ago.

If I could swing all four arms to the same side of the lift, the car's center of mass would be frighteningly far from the lift posts. I don't like that idea much.

jebdog

On the rear lift on the forward lower suspension arm mount it is farther back and inward but a major structural element for the suspension.

daveo90s4

The w'shop manual shows two rear jacking points - the normal location we all know about, plus another further inboard of each normal rear jacking point. The 'inboard' ones are, I see, recommended for when lifting the vehicle on a hoist. Because they are further inboard, the effective length of the rear lift arms is longer. So if the rear lift arms are too long to get on the 'normal' jacking points they may not be too long to get on to the inboard lifting points.

Regards
Dave Overington
90 S4
Australia

Garth S

That is a good point - the reference is WSM vol 1, pg 0.1 - "Lifting car". .... strange place to look up - the title is soooo misleading ....
The lift point referred to in not so much further inboard as it is further rearward .... it is the forward mount bracket for the rear lower control arm, a most sturdy spot to place a lift.

MBMB

The car will go up on the B2900 lift if I put the front arms under the jacking points and the rear arms under the lower control arm bracket. Now I need to figure out where the best place for the lift will be. (Note to self: next time you build a garage, make it two feet longer than you think is necessary. :-P )