Msport

Further to the above, Corner Weighting will not improve the handling of the car per se. It is a bit like saying more power will make you go faster! The grip that a car can generate depends on the vertical loading of it's tyres - an axle will have it's greatest grip when the tyres on that axle are evenly loaded. (Milliken & Milliken wheel pair theory) Load transfers in a vehicle normally occur diagonally accross the vehicle - hence corner weighting is usually carried out to give a 50% cross weight. The reason for this is so that the car will react the same in both right and left turns so the chassis engineer can then apply understeer/oversteer corrections to dial this out. A typical example of incorrect corner weights is when a car will be fine in right hand turns and understeer/oversteer on left hand turns - this is very difficult to dial out. The chassis tuner can also 'add wedge' (alter the cross weight percentage) for certain tracks so the car will turn better in right or left hand turns (most UK circuits run clockwise - Mallory is a good example of when you would not run a 50% cross weight) and also add 'stagger' (different tyre pressures to change rolling diameters of wheels) to improve drive out of the corners. Due to the fact that corner weighting is done to equalise load transfers so that each tyre 'sees' the same vertical loadings it is vital that the part of the suspension responsible for the load transfers is tested first - i.e. springs/dampers. Unless you know that the spring ratings are identical and the dampers are well matched by a damper dyno (even top grade dampers require dyno matching) then the corner weighting will be an approximation at best. The car should be weighted for it's running conditions - we weight ours for the last 25% of a race - fuel is measured accurately to the nearest litre as is driver weight/helmet etc - it is vital these weights are placed in the correct position during the excercise. As previously stated the vehicle should also have adjustable ARB droplinks to corner weight - the ARB's are disconnected for corner weighting to stop inaccurate readings then re-connected with no pre-load.

Thanks for the reply Tony - I agree the SAI does change dynamically in bump/droop but not as a result of steering wheel input but as a result of weight transfers.

Tony, I'm sorry but I don't agree! The SAI never changes on the vehicle - it is set by the positions of either the top & bottom ball joint in a double wishbone set-up or the bottom ball joint and top of the Mcpherson strut. No matter what steering angle the vehicle assumes this angle stays the same. As the wheel is turned it gains and looses camber - it is therefore the included angle that changes (SAI + Camber) and NOT the SAI. Likewise the definition of caster is: The angle in side elevation between the steering axis and the vertical. Therefore no matter what steering angle is applied the castor angle remains the same - unfortunately the Hunter machine does show the castor reading changing but the actual angle remains the same - this has been highlighted to Pro-Align. The 'axis' remains the same - it is the stub axle's relation to this axis that changes. (and how the Hunter measures caster) Regarding the gain/loss of camber (or migration as you incorrectly call it as they do not gain and lose at the same rate in dynamic situations due to body roll). The suspension is designed so the outside (loaded) wheel gains negative camber in the turn whilst the unloaded wheel increases positive camber - this is good because as the chassis rolls you want the unloaded wheel to become more vertical so its contact patch increases.