F.A.O. madisonmonkey & guv (Anti lift kit, alternative views)
19 October 2008, 09:40 PM
#1
F.A.O. madisonmonkey & guv (Anti lift kit, alternative views)
Had to put this here as too big to prvt msg! Others feel free to comment on subject also.
Just a few extracts from an old thread on ALK (Pro-Lift). Yes its advantageous & improves turn in & reduces understeer, but is it essential & what it does can be achieved with a good coilover setup & thats without reducing the built in anti dive & without dropping the suspension mount points. I prefer a flatter feel & dont want increased lift & dive just to reduce understeer, there must be a better way to do this i.e good coilover setup & thicker adjustable ARB?
From here:
https://www.scoobynet.com/suspension...-lift-kit.html
ANDY F- SUBARU TUNERS
"The main benefit is from the stiffer bush reducing castor change under braking/power. There is also a slight increase in castor due to the strut bottom being pushed forward slightly. This can improve 'feel' with the standard over assisted steering.
Contrary to popular belief the 'anti lift kit' does not actually reduce lift !!! In fact if you work out the geometry (and I have) it actually increases the lift/dive moment arm (CG height/Instantaneous pitch centre) under acceleration or braking conditions."
"It seems to me that by lowering the rear mount you will increase dive & squat (in theory), and will have virtually no effect on castor for the small amount of lowering involved. Has anyone measured a castor change?
I'd suggest that the active ingredient in the ALK is the stiffer bush and that the small change in geometry is insignificant and further-more if you want to reduce dive/lift then the rear mount should be raised (not lowered) relative to front mount."
"I think I can see where you got that from, if you look solely at braking then if you kept increasing anti-dive you would eventually get pro-lift ie hit the brake and the nose of the car would lift. When you reverse the longditudinal force (acceleration) you also reverse the vertical component and anti-dive forces become anti-lift forces.....it follows that any reduction in anti-dive = a reduction in anti-lift.
As a practical experiment (not suggesting this for you Jim) try pulling on the handbrake on a Peugeot 206 (or probably any modern small FWD car) whilst going forward (slowly )....result - **** dips sharply (dive / squat)
Reverse the force by doing it with the car rolling backwards and **** leaps up (lift)
WHITELINE AUTOMOTIVE
"I have to admit that the basic conclusion is a little embarrassing when compared with the existing text of the product description. Specifically, our testing data found that the fitment of the ALK increases from lift under power while reducing understeer and delivering the positives described by customers and quantified thru extensive track testing. How to answer this apparent contradiction?
The basic design for the ALK was done over 5 years ago with the help of a consultant. During the initial research stage we referred to the concept as an “anti-lift kit” meaning that it dealt with the geometry of “anti-lift”. The concept delivered the dynamic results we wanted with reduced lap times and understeer however the name stuck through. A great deal of time and further research has since been invested yet the description has remained unchanged. Our apologies for any confusion we have caused in the meantime but we very much appreciate the opportunity to revisit the issue and learn from this debate. Here are the key excerpts from the report we prepared;
------------------------------------------------------
Effect of Whiteline Automotive ALK
The ALK effectively modifies the position of the side view instant center on the front suspension. The side view instant center is the pivot point for the side view swing arm (also the pivot point for the suspension at that instant), which is a line drawn from the tire contact patch to the side view instant center. The slope or angle of this swing arm (effectively the position of the instant center) describes the amount of anti-dive and anti-lift present in the front suspension.
The instant center is found by the intersection of the two lines. The first is the projection of the lower control arm, say through the chassis mounts, behind the front wheel the second is the normal to the axis joining the tire contact patch to the top of the strut tower, from the top of the strut tower.
(Note: To be absolutely correct these lines should be projected onto the wheel center plane, so any lateral angles in the lower control arm will effect the instant center position. However the lower control arm in the WRX is relatively flat which will give minimal effect)
Together with the position of the instant center, the WRX’s wheelbase, CG height above the ground, % front torque (for anti-lift) and % front braking (for anti-dive) are required to calculate the anti features of the front suspension.
With the ALK fitted, the rear mount of the front lower control arm is lower by about 20mm. There is also a castor change by moving the mount outwards (however this has not been taken into account). This has the effect of lowering the instant center and decreasing the angle or slope of the swing arm resulting in the following anti-dive and anti-lift coefficients, expressed as percentages.
As can be seen in the above calculation spreadsheet (can supply separately as can not embed into message), with the ALK fitted the anti-lift and anti-dive coefficients reduce to 0%.
The effect of lowering the % anti-lift / anti-dive
If the suspension has 100% anti-dive / anti-lift, then all the longitudinal load transfer experienced when braking and accelerating is carried through the control arm, leaving the springs unloaded and no deflection present. If there is 0% then the springs take the entire load, giving full spring deflection.
By lowering the % the front suspension becomes “softer” under acceleration or braking. This gives rise to the higher diving and lifting that has been experimentally shown. (These results are also in a table
A softer front suspension during acceleration and braking will even out the load on the front tires, giving a higher total cornering load available or more front grip. This will lead to less understeer when cornering under power or brakes.
Softer front rate will also allow better wheel tracking over rough roads, keeping the wheels in contact with the ground. In simple terms, fitment of the ALK has the effect of delivering a softer effective spring rate during the pitch moment.
------------------------------------------
From this you can see that the product name is misleading and inappropriate. This will be changed and qualified even though it deals with the geometric concept of “anti-lift”. However we can happily report that the improvements claimed for the product are still valid and quantifiable.
I look forward to continuing this discussion once everyone has had a chance to digest the above.
Best regards
Jim Gurieff
Whiteline Automotive
911- SUSPENSION GURU!
"Don't bother with them, fit Noltec top mounts and get rid of understeer.
Graham
ZEN PERFORMANCE
"no ALK for me then
So Noltec allows you to adjust the castor? Is that correct?
On the fronts yes david
"Hi,
If you don't want to get rid if the 'anti' geometry, Whiteline also manufacture a castor (KCA375) bush that leaves the pick-up point at the original height.
This will give about 0.5 degree of static castor and more importantly, reduce the castor loss under cornering load.
The main reason for wanting increased castor for me is not the increased negative camber on the outside front wheel but the increased load on the inside front wheel during cornering. The reduced 'anti' geometry helps this effect of castor to 'push the inside front wheel down' to increase front end grip and traction.
Just a few extracts from an old thread on ALK (Pro-Lift). Yes its advantageous & improves turn in & reduces understeer, but is it essential & what it does can be achieved with a good coilover setup & thats without reducing the built in anti dive & without dropping the suspension mount points. I prefer a flatter feel & dont want increased lift & dive just to reduce understeer, there must be a better way to do this i.e good coilover setup & thicker adjustable ARB?
From here:
https://www.scoobynet.com/suspension...-lift-kit.html
ANDY F- SUBARU TUNERS
"The main benefit is from the stiffer bush reducing castor change under braking/power. There is also a slight increase in castor due to the strut bottom being pushed forward slightly. This can improve 'feel' with the standard over assisted steering.
Contrary to popular belief the 'anti lift kit' does not actually reduce lift !!! In fact if you work out the geometry (and I have) it actually increases the lift/dive moment arm (CG height/Instantaneous pitch centre) under acceleration or braking conditions."
"It seems to me that by lowering the rear mount you will increase dive & squat (in theory), and will have virtually no effect on castor for the small amount of lowering involved. Has anyone measured a castor change?
I'd suggest that the active ingredient in the ALK is the stiffer bush and that the small change in geometry is insignificant and further-more if you want to reduce dive/lift then the rear mount should be raised (not lowered) relative to front mount."
"I think I can see where you got that from, if you look solely at braking then if you kept increasing anti-dive you would eventually get pro-lift ie hit the brake and the nose of the car would lift. When you reverse the longditudinal force (acceleration) you also reverse the vertical component and anti-dive forces become anti-lift forces.....it follows that any reduction in anti-dive = a reduction in anti-lift.
As a practical experiment (not suggesting this for you Jim) try pulling on the handbrake on a Peugeot 206 (or probably any modern small FWD car) whilst going forward (slowly )....result - **** dips sharply (dive / squat)
Reverse the force by doing it with the car rolling backwards and **** leaps up (lift)
WHITELINE AUTOMOTIVE
"I have to admit that the basic conclusion is a little embarrassing when compared with the existing text of the product description. Specifically, our testing data found that the fitment of the ALK increases from lift under power while reducing understeer and delivering the positives described by customers and quantified thru extensive track testing. How to answer this apparent contradiction?
The basic design for the ALK was done over 5 years ago with the help of a consultant. During the initial research stage we referred to the concept as an “anti-lift kit” meaning that it dealt with the geometry of “anti-lift”. The concept delivered the dynamic results we wanted with reduced lap times and understeer however the name stuck through. A great deal of time and further research has since been invested yet the description has remained unchanged. Our apologies for any confusion we have caused in the meantime but we very much appreciate the opportunity to revisit the issue and learn from this debate. Here are the key excerpts from the report we prepared;
------------------------------------------------------
Effect of Whiteline Automotive ALK
The ALK effectively modifies the position of the side view instant center on the front suspension. The side view instant center is the pivot point for the side view swing arm (also the pivot point for the suspension at that instant), which is a line drawn from the tire contact patch to the side view instant center. The slope or angle of this swing arm (effectively the position of the instant center) describes the amount of anti-dive and anti-lift present in the front suspension.
The instant center is found by the intersection of the two lines. The first is the projection of the lower control arm, say through the chassis mounts, behind the front wheel the second is the normal to the axis joining the tire contact patch to the top of the strut tower, from the top of the strut tower.
(Note: To be absolutely correct these lines should be projected onto the wheel center plane, so any lateral angles in the lower control arm will effect the instant center position. However the lower control arm in the WRX is relatively flat which will give minimal effect)
Together with the position of the instant center, the WRX’s wheelbase, CG height above the ground, % front torque (for anti-lift) and % front braking (for anti-dive) are required to calculate the anti features of the front suspension.
With the ALK fitted, the rear mount of the front lower control arm is lower by about 20mm. There is also a castor change by moving the mount outwards (however this has not been taken into account). This has the effect of lowering the instant center and decreasing the angle or slope of the swing arm resulting in the following anti-dive and anti-lift coefficients, expressed as percentages.
As can be seen in the above calculation spreadsheet (can supply separately as can not embed into message), with the ALK fitted the anti-lift and anti-dive coefficients reduce to 0%.
The effect of lowering the % anti-lift / anti-dive
If the suspension has 100% anti-dive / anti-lift, then all the longitudinal load transfer experienced when braking and accelerating is carried through the control arm, leaving the springs unloaded and no deflection present. If there is 0% then the springs take the entire load, giving full spring deflection.
By lowering the % the front suspension becomes “softer” under acceleration or braking. This gives rise to the higher diving and lifting that has been experimentally shown. (These results are also in a table
A softer front suspension during acceleration and braking will even out the load on the front tires, giving a higher total cornering load available or more front grip. This will lead to less understeer when cornering under power or brakes.
Softer front rate will also allow better wheel tracking over rough roads, keeping the wheels in contact with the ground. In simple terms, fitment of the ALK has the effect of delivering a softer effective spring rate during the pitch moment.
------------------------------------------
From this you can see that the product name is misleading and inappropriate. This will be changed and qualified even though it deals with the geometric concept of “anti-lift”. However we can happily report that the improvements claimed for the product are still valid and quantifiable.
I look forward to continuing this discussion once everyone has had a chance to digest the above.
Best regards
Jim Gurieff
Whiteline Automotive
911- SUSPENSION GURU!
"Don't bother with them, fit Noltec top mounts and get rid of understeer.
Graham
ZEN PERFORMANCE
"no ALK for me then
So Noltec allows you to adjust the castor? Is that correct?
On the fronts yes david
"Hi,
If you don't want to get rid if the 'anti' geometry, Whiteline also manufacture a castor (KCA375) bush that leaves the pick-up point at the original height.
This will give about 0.5 degree of static castor and more importantly, reduce the castor loss under cornering load.
The main reason for wanting increased castor for me is not the increased negative camber on the outside front wheel but the increased load on the inside front wheel during cornering. The reduced 'anti' geometry helps this effect of castor to 'push the inside front wheel down' to increase front end grip and traction.
Last edited by rickya; 19 October 2008 at 09:59 PM.
arrrhhhhhh
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