S4 static ride height

[JohnMorin]

Hi

My S4 is almost ready to go back on the road. One of the jobs I have left until last is tightening all the wishbone and A-frame bolts. Having checked the factory manual I checked my car to find that both the front and rear are already below the figures stated in the manual, the front by about 1/8" and the rear by about 1/2". The car doesn't look as though it is sitting oddly.

Should I just tighten them as they are or is something amiss here?

Thanks

John

[661]

Do you have adjustable spring platforms?
Do the wishbones look as if they are sitting below the horizontal at the chassis ends?

[JohnMorin]

Hi

No adjustable spring platforms, everything is standard apart from Koni dampers. Standard wheels with 155/80 13 tyres correctly inflated.

The front lower wishbones are at about 10 degrees to the horizontal with the outer ends lowest. The rear A-frames are about 5 degrees to the horizontal with the outer ends lowest.

Thanks

John

[661]

Good point mentioning the tyres, apologies for that omission.
The geometry sounds pretty close, indeed it may verge on suggesting a slightly raised ride height, which is not the impression from the body height.
If the body is spaced correctly I would just tighten everything up at this height, run it for a few miles and see where it settles. ( you may need to loosen and re tighten wishbone bolts) I think the suspension geometry is more important than the actual body heights, although aesthetics and tyre clearance is to be borne in mind.
I like to run with some rake, ie the rear up a bit. You may find you need/want to lift the rear a fraction. Tricky spring length equation without adjustable platforms, or the use of spacers, easier with narrow springs.

[JohnMorin]

Ok, thanks. I'll tighten it all up and see how it goes. From memory l remember that understeer was definitely not a problem, I would suspect that raising the rear would tend towards oversteer given that the rear centre of gravity would rise, I don't want that, neither do I want to spend a fortune on suspension components especially as I have now put it all together.

John

[661]

We've only spoken of ride height.
Your vital alignment is another story

[JohnMorin]

Hi

I take it by vital alignment you mean toe, castor, camber etc.

Not something I can measure with any real accuracy myself but one of the first places I will be taking the car is somewhere with decent wheel alignment equipment to see how it is sitting, front toe will definitely need adjusting as the track rod ends have been renewed. I do have experience in that area having been involved the the provision of data for 3D WA machines. The car has a Spyder chassis which has never had any use, I checked all the wishbones for wear and straightness and all seems OK.

I measured the body ground clearance today at either end of the sill and the front is 160 mm, the rear 170 mm so I do have some rake.

Until I get it on the WA machine and drive it I don't think I am going to be able to make any decisions about changing anything.

John

[661]

In the first post you stated that you were below the 'stated ride heights'.
These last measurements are above what I would consider the accepted road ride heights of 6" ( 150mm) front and back.
I'd just run it, let it settle and see where you are.
Consider castor fixed.
Front toe is easy to adjust, rear toe and both cambers would need adjustable wishbones to adjust. There will be some influence on some of these by altering ride height which why it's probably best to let that get to where you want it first. I would not drive the car in a spirited manner until the alignment is checked.

[JohnMorin]

In the first post you stated that you were below the 'stated ride heights'.

Those measurements refer to the places specified in the workshop manual for setting the static ride height with blocks of wood, that is under the rear struts and under the front trunnions.

I measured the body ground clearance today at either end of the sill and the front is 160 mm, the rear 170 mm so I do have some rake.

These measurements refer to the distance between the body measured under the sill behind the front wheel and in front of the rear wheel and the ground.

So I'm thinking that the figures in the manual refer to a newly built car, one with new springs all round. Over time there will be settlement which is where my car now sits. So I will tighten as is and see how it goes.

Thanks for your input

John

[661]

I assumed you were using the sill height from the floor in your first comment. That is the usual measure.
I don't consider trunnion and strut heights useful for ride height as they are outboard and relatively static (Tyre sidewall depth being the major contributor to their position)