Dude,
Get a small length of 2X4, and run the front wheel/tire over it and jack up the front side of the car to address one side at a time. I don't believe that applying pressure to the middle side is the way to go.
You can jack up the entire back side of the car by putting your jack on the "pumpkin" differential. But if you want to save a little time, just run the front wheel over a 2X4, jack up the car from the front jack point, and you'll have both wheels up in the air. As you know, the car frame is stiff, but use jack stands for safety.
Work on one side at a time for the garage floor mechanic. My S is lowered because I have the KWs as low as suggested and I can't get a jack under any jack point until I run over a 2X4. So, what I do now is jack up the front and work on one side at at time. It works well. I do both front and back on each side at a time.
Before each track event, I go for the work required on the right side, then do the work on the left side to include all fluid changes and exhaust mods.
One side at a time.

CB

 

Why not?

 

It also "doubled" the load on the welded box spanner Increasing the shear forces that it saw by quite abit (ADDING the weight of the lower level).

Multiplication or in this case the use of the word doubling is misleading. Force is being added not multiplied. The planned for shear was the weight of the platform P1 against the spanner mounting point. With 2 platforms hanging from a single spanner mounting point the weight of the shear increased by the weight of a second platform P2. resulting in P1 + P2. If the assumption is made that both platforms are pretty much equal in weight and distribution then you get P + P = 2P.

If the box spanner was reinforced enough between the two mounting points then it likely would not have deforemed enough to cause the failure that occured.

I'm pretty sure it wasnt the nut and washer that failed but the deformation of the spanner box that resulted in the failure. The nut and washer were pulled thru the spanner.

Spanner box = spacer, for this argument.

In the case of the spacer the maximum shear force (that exists between two adjacent mounting holes) with pass thru studs is zero. Regardless of the lateral forces the studs/hubs/wheel see.

In the case of the H&R mounting method the shear force seen by the spacer goes from zero (with pass thru studs) to some new maximum value proportional to the substantial later grip of the slicks.

And, each hole pair will see substantial shear cycle with each rotation of the mounted wheel during high lateral G turns.


I've pulled this off the top of my head, or out my ass, and likely have gotten some aspect of it wrong. But i'm pretty sure the gist of it is correct.

 

What shear forces do you mean? The spacer will carry the same circumferential shear loads either way. The thrust/braking forces are being carried by friction. The studs are just carrying a tension force that provides the normal force for the friction surfaces.

So the spacer is in circumferential shear either way, as it is transmitting the thrust forces from the rotor to the wheel.

What is different is that in the case of the pure spacer design it is not carrying any of that tension load. Instead, it is in pure compression. In the H&R design it is carrying all of that tension load and is not in compression at all. There will be an axial-direction shear between the studs pulling in to the hub and the studs pulling out to the wheel.

The internal loads in the H&R spacer will be much higher than in the pass-through spacer.

 

I vote pass-through spacer and long studs, though neither is ideal.

 

well the reason for the spacer is so that you now have 4 of the same wheels instead of different front and rears.

So imo thats more "ideal"

 

True. I'd do either for that reason.

 

Because it doesn't appear that the middle - underside has the construction to handle a single lift-point.

CB

 

"Appears"

Many of us have been lifting from there for over half a decade. I don't even trailer my car to the track, so for me it's two to three tire changes a weekend. There is NO issue jacking the car from there.

 

[QUOTE=msm_s2k,Nov 4 2006, 08:24 PM]"Appears"

Many of us have been lifting from there for over half a decade.