e34 up in the air...

[gmu525i]

I finally stopped procrastinating and started on the suspension overhaul today.

Step one: get the car up in the air. The front is easy, but the back was a huge pain. The sub-frame is too far underneath to reach with the jack from the back, so I wound up putting a jack on each side to get it up high enough to get a small set of stands in, then repositioned a jack to the center of the rear sub-frame.

The problem now is that I can't figure out anywhere to put the jack stands in the rear besides the sub-frame by the mounts, or the points for the factory tire-change jack. The sub-frame by the mounts appears to be a great option, except that I am planning to replace the mounts, so the sub-frame has to be free to be dropped.

The factory jack points are an unhelpful shape, and it's not clear if the area around the cylindrical indentation (matching the shape of the jack) is equally as strong as the center, or if the indentation is just a locating device.

So far the Internet has not been any help. It's not even clear to me where you would locate the pads on a post lift.

[gmu525i]

I have plenty of time to work on this project, so I decided to spend the morning figuring out the jack stand situation.

After pondering the design of the factory jack, I decided to fabricate some wood blocks out of pressure treated lumber that would fit into the factory jack points. While there are certainly a variety of opinions out there on the various forums regarding the use of wood blocks with jack stands, after talking to friends with knowledge of structural properties of treated lumber it seems that it mostly comes down to ensuring that the grain is correctly oriented, avoiding any cleaving or shearing forces, using correctly rated lumber, and ensuring that there is as much flat surface contact between any loosely coupled components as possible.

I attached some pictures of what I came up with, and so far it seems to be quite sturdy. After leaving the car on the first block I made for about an hour, I lifted the car up and inspected the block, and did not note any deformation of the wood. After putting both blocks in place I let it sit for a couple of hours before actually working under the car so that I can check for settling behavior, and so far none has been noted. Also, no deformation has been noted in the other blocks I made as adapters for the curved-top jack stands. Shaking the car fairly vigorously does not produce significant movement.

Depending on how motivated I am at some point I may decide to improve the design further to tighten the coupling between the stacked wood blocks to really really ensure that they can't go anywhere, but I think it's OK for the moment.

Maybe I will actually start taking parts off the car soon.... ;-)