Tracking

[chiefmechanic]

Can anyone tell me if the wheel alignment figures for the Audi s2 are the same for a 1993 s4
Changed the two rear upper link arms on the suspension of my 1993 s4 and am looking to get the car tracked now. Does anyone know the correct alignment figures for front and back. Brian

[UrS4boy]

OE C4 UrS4/S6 Alignment Specs

...Changed the two rear upper link arms on the suspension of my 1993 s4 and am looking to get the car tracked now. Does anyone know the correct alignment figures for front and back? Brian

Yup

OE C4 UrS4/S6 specs:

========================================
FRONT:
Camber -1º 15' to -0º 15'
Caster +0º 15' to +1º 35'
Toe +0º 03' to +0º 10'
Turning Angle Diff -1º 40' to -0º 40'

Cross Camber -0º 30' to +0º 30'
Cross Caster -1º 00' to +1º 00'
Total Toe +0º 05' to +0º 20'
========================================
REAR:
Camber -0º 30' to +0º 00'
Toe +0º 00' to +0º 10'
Total Toe +0º 00' to +0º 20'

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Good luck. Make sure your brakes and tires are up to tracking.

[Error404]

Note for reference they are not the same as S2 settings though!

[Rusty]

<1 deg castor

[jaychen]

I've got no idea how each of the values affects the driving of the car.

@rusty can you elaborate?

[Rusty]

AFAIK and in basic terms:-

Camber affects cornering grip but also the ability of the tyre to put the power / brakes on the road. More camber gives better cornering but uses less of the tyre in a straight line. I refer you to F1 at Spa 2012, where camber was a big issue. More complex suspension setups tend to try and ensure that camber increases with suspension travel, rather than decreasing or even going positive (top of the wheel is more outboard than the bottom). 60s british sports cars suffer horribly with this effect, MacPherson strut is a lot better but sill not great, dual wishbone setups are far superior.

Castor affects the centring action of the steering, as well as the dynamic camber (when turning) and steering weight. FWD cars tend to have less castor, as the increased camber that occurs when turning the wheel gives less grip due to the reduction in contact patch. On RWD cars, the front wheels do less work, so they tend to run more castor. FWD/4WD = 1 to 5 deg (S2 = 1.5, 172 Clio = 3, TT = 6?) RWD 5 to 10 deg (BMW = 8-9).

Toe affects the stability of the car and the keen-ness of the car to turn in to a corner / hold the line of the corner. Toe out (front of the wheels are further apart than the rear) makes for a less stable, more pointy car; toe in adds straight line stability. Most suspension setups have dynamic effects due to different mounting points for track control arms. On an S2 coupe, this makes the rear go toe in under acceleration and toe out under braking, hence why you can get a coupe to lift off oversteer like a hot hatch but under power, they're very stable...