axle stand point

Nearly all VWs are like this AFAIK - 4 circular jacking points. They're designed to be easily serviced with a 2 post lift (4 arms that swing out to meet the circular pads). On my MK2 there's a lack of one at the back, but it's not a horrific bodge to use a suspension mount.

The axle stand / jacking point conundrum is a PITA. I tend to jack off the suspension mounts then drop the car onto an axle stand on the jacking point. Cars are designed to be serviced on lifts now, so the manufacturers tend to skimp on proper jacking points. The sill points and supplied jack are alright for changing wheels, but they're not much use for anything else, unless you have a suitably shaped head for a trolley jack.

Thanks AC :@)

I really dont like jacking on suspension points - they are generally for taking forces in the same plane as the floorpan of the car, not vertically. Take, for example, the main wishbone pivot points. They look fairly hefty on my car but all the force from an impact actually goes up through the shock into the turret - the pivot location only controls the front to back and side to side movement of the arm - low forces. If im jacking and axle standing I use the main subframes on my car to jack then axle stand onto the wishbones as close ot the wheel as possible. This isnt ideal unless you watch them carefully though - unlike a lot of cars my wishbones are only just off-horizontal (about 15 degrees) when fully suspended so unlikely to slip during loading. My old peugeot had them at about 45 degrees and I'd have used the pivot points on that. Common sense really I suppose.

They'll bend quite quickly then, they take forces in the plane of the wishbone.

Now the wishbones aren't designed to take that bending moment :-)

Duncan Wood proclaimed to uk.rec.cars.maintenance ...

No, the wishbone mount points are only to hold the arms still while they rotate about that point, and to prevent the relatively small radial forces presented during normal driving position (wishbone flat). Clearly there ARE some radial forces but nothing like the weight of the corner of the car. With the wishbone flat almost all of the force is transmitted vertically through the hub area, up through the strut to the towers, and next to zero is converted to radial force on the inboard wishbone joint.

Not if you jack it at the outside edge as I said, that way the force is transmitted through the bottom ball joint and up through the strut as it is in normal driving. Jack it half-way and yes you impart a large bending moment on the wishbone. Mind you, looking at mine they are 2.5mm box section steel (about 4x1 inches) and weigh in at about a kilo each despite only being short - id probably risk lifting the whole car on one lol.

__ J __________________________________________

Till you hit a bump. If they where that lowly stressed they wouldn't need M10 bolts.

I'll happily bet the inboard arm pivots more structural than the wishbone. Anyway if you jack it half way along one half the force will end up on the inboard joint.

Duncan Wood proclaimed to uk.rec.cars.maintenance ...

Even when you hit a bump the forces are not that great, and tend to rotate the arm backwards, pivoting it in the plane of the floorpan, as i said from the start, not loading it directly upwards like a jack does. M10 bolts are piffling, but used partially because they fit neatly through a bushing which has to be fairly large in internal diameter to be clamped in place properly.

Lets just think about this - you're telling me arms transmitting the force are less strong than the thing they are transmitting the force too? :-) Wild sweeping statement, which depends how they are loaded to determine if you're right. However I'll happily bet that neither are designed to take vertical load on them of the order of magnitude presented by the weight of one end of the car. People seem to assume that wishbones and inboard joints take huge loads - they dont, they are just pivots to help guide forces up the strut, and are designed specifically NOT to interfere with the load carrying of the strut. I use my wishbones, but only at the far end. My wishbone inner pivots are noodly protrusions from a main chassis area, if you jack on them you can visibly see them flex in a vertical plane.

If you impact a pothole/brick in the road the outer end of the arm goes diagonally back and up. This resolves to two component forces in the floorpan plane and the vertical plane. The vast majority, the floorpan plane, is taken up the strut, the rest goes into a sideways bending moment of the inboard pivot. At no point does the inboard pivot take a noticable vertical load (unless of course you take the suspension to the its very extremes, where you are likely to rip the thing off or cause lasting damage for that very reason).

Now try clipping a brick sideways. You can apply some really quite large forces, hence why a 30cm long strut ends up being 2" square. The dynamic loads are far higher than the static ones.

Duncan Wood proclaimed to uk.rec.cars.maintenance ...

I'm not sure how you clip a brick sideways?! But generally sideways impact do large amounts of suspension damage - this is why when you see cars slide round bends and knock into kerbs they often cause terminal suspension damage. Someone in my family has had this happen on two occasions. Hit that same kerb at the same speed relatively straight and no damage will be done as the loads are taken correctly. Dynamic or static is of little relevance, its the direction in which the force is applied that matters, and a sideways impact on anything is not what the suspension is designed. It still wont load the inner joint in very much of an upward direction unless your suspension is set, at rest, to have severe wishbone angles - common of vans and 4x4s, but not so much on normal cars.