Toe angle change Vectra C if not weighted correctly

[NickT]

Just a quick question Tony

 

My car is a Vectra C 3.0 cdti v6 on a 57 plate. I've noted that the car should have weights in the front and ideally have half a tank of fuel to have the geometry set correctly.

 

If the car had the geometry done on a hunter machine without the weighting, how much would it affect the toe angles at the front?

 

Also, another question. If the car is weighted with 70kg both sides, what effect would it be to transfer the weight all to the drivers side and take into account the crown angle of the road?

 

NickT

 

ps I do apologise for a sensible post. I'll get to posting inane crap and awful jokes later on

[Tony]

The pre-loading is to position the suspension between bump and droop so it's more a camber based measurement rather than toe. On most cars we pull down and push up the unsprung chassis to observe the toe tenancy on and off bump.

 

Theoretically the road crown differential should be lost in the independent suspensions loading but there would be a difference in the caber positions and the tyres lateral shape. On some cars the camber and castor angles are slightly staggered but only slightly otherwise corning would be effected.   

[NickT]

So Tony, the values observed with front camber were more on the "within spec" but at the more "positive end" of the camber range.

 

If it was pre loaded then I can understand the equal distribution of weight wrt drop and change of camber on the ramp that is calibrated flat, in an ideal situation.

 

But, what about the distribution of weight to the drivers side only and road camber and the change to the cars camber?

 

I assume that the side with the greatest negative camber induces a pull to that side so the corrective action is to move the when to the right by about 2 degrees. This is what's happening on my car but it feels like it's toe effect.

 

Ps I apologise profusely for another sensible post. ..

[Tony]

As odd as reads the drivers weight moves the camber transversely.... There would be little gain on the OSF but much more negative gain on the NSF, 

[NickT]

If there is more negative gain on the NSF would this not induce the car to move to the left, so a corrective action to hold the dyeing wheel to the right slightly be the net result?

[Tony]

The conical effect of negative NSF camber would push right..... To me the angles tolerance is the dynamic range the camber moves during the suspensions transitions and if you think about it as each wheel independently hits a bump and gains negative camber the car doesn't bolt off to one side does it.

[NickT]

No it doesn't Tony.

 

I am wondering now if the wheel want set perfectly straight before setting the geometry and the electro pneumatic steering is doing the "pull"

 

I'll have a go at adjusting the track rod ends to centre the steering and see if the effect goes away