Anti Lift Castor Kit

Background.
The current WRX, Impreza, Liberty/Legacy/Outback and Forrester are based on the same floor pan as released on the original Liberty in 1989. That's why many of the suspension parts are interchangeable. The original platform was not designed for performance, but rather for reliability, potential ground clearance, passive safety and above all else, ease of manufacture.

The front geometry was maintained with struts and a Y shaped lower arm which reflected the industries change to unrestricted crumple zones for better energy absorption in frontal collisions. The arm is located at the front by the pressed metal cross-member and by the floor pan at the rear. The last branch of the Y locates the bottom of the strut allowing the wheel to be controlled in a fore-aft direction while the arm pivots at the front and rear locating point, allowing vertical wheel travel through bump. The original geometry of this arm and its subsequent operation meant that the designers had provided (albeit unwittingly) anti-dive, better off-road "clamberability" and a lower centre of gravity at the front.

More importantly however, there was an issue of packaging, how to fit a larger engine lower with out also having to modify the floor pan and rear pickup point. One of the costs for this design compromise was front lift under acceleration. Being the original 2.2litre Liberty, gross acceleration and resulting front lift was hardly a major compromise at the time but then along came the RS followed by the WRX. These cars were/are performance bargains because Subaru changed what it considered as important/cheap, but left other items that they felt would not greatly detract from the overall performance.

Handling Issues.
The WRX is a poor handling car with great grip. In a pure sense it does NOT handle well, but is saved on the limit by its all wheel drive. It will not please WRX owners to know that the WRX is consistently knocked off at the race track (tarmac) by 200SX's and many others, but they lead on the dirt. Again, more grip than handling. The WRX really tested the original design because of its enormous acceleration. As any WRX owner will confirm , powering out of corners means nose up and loads of understeer as the weight shifts to the rear and the front tyres scrub for traction. Power launches will see the nose lift while 70% of the available torque tries to find a release through the front wheels. These are the very symptoms that has been succeeded in doing with the anti-lift kit. I will not go into the specific geometry changes made by the kit, but those that are interested should look underneath a current (new) Outback (and STi if available) and compare the rear of the front control arm mount on the Outback with that of their WRX, Liberty etc. The problem still exists on the Outback and STi, however the STi models with alloy arms have stiffer bushings, this is better, but they STILL benefit form the part.

How the Kit Works.
So, the anti-lift kit changes the location and geometry of the control arm pick-up point to remove the "lift" resulting from the original geometry. The new mount also relocates the arm in another plane to add 0.5 deg. static positive castor. The new mount also features a performance polyurethane bush which replaces the original high compliance rubber type.

This serves to maintain a closer link between static and dynamic alignment settings through reduced compliance and distortion under load. The 0.5 deg. additional static positive castor coupled with the low compliance bush means over 1.0 deg. more positive dynamic castor.

If you don't know the benefits of positive castor, see MRT "how it works" separately about this, or ask someone that does race car prep. I hope I have adequately explained what the anti-lift kit does. To put this into perspective, you have to also understand that every car is designed to a compromise.

Products are available for immediate purchase on-line at the MRT-Shop. Hundreds of items with photos available now. Both Australian and International shipping is no problem.

A Word on Ride Quality.
Moving the "compromise" toward better handling would suggest a deterioration in ride, but not exactly true. Technically, the ride does NOT change because we are not changing spring, shock or sway bar rates which are the main factors in ride compliance. In fact, the change of geometry through the use of the anti-lift mount marginally improves (more direct) the relationship between wheel and strut, making it easier for the strut to respond to wheel travel/bump.

The downside is actually in levels of NVH or noise, vibration and harshness. In this area there is a 10-15% increase in NVH (felt through wheel and cabin according to MRT's tests) as the new low compliance polyurethane bushes do not absorb as much NVH as the original rubber. But then again, that's why they work better in the handling department, specifically in steering turn-in.

From a big picture point of view, it may interest you to know why we went down this development path in the first place. Our fleet WRX was first used to develop a full handling package back in September '97. We found that we had to disproportionately increase rear spring and damper rates to slow down rear squat in response to front lift. This also meant higher front damper rebound rates to slow down front lift, all of which meant that we had to apply "band-aid" solutions to the symptoms rather than fixing the actual problem. The result was greatly improved handling at the expense of ride comfort due to the high rear spring and damper rates.

Tests using constant average lateral G force measurement proved that our suspension combination had the goods in the handling department. But, we pride ourselves on providing the best ride/handling compromise in the industry so we started the search for a true solution to the problem. January saw us making our first long term development prototype of the anti-lift kit. The prototype worked even better than expected, forcing us to change ALL spring and damper rates (softer) as the original problem was pretty much fixed.

This is why we have so much confidence in the product as the best compromise solution to ride and handling. With the anti-lift kit we can maintain the same high constant lateral G's as before but with decent ride quality.

ACKNOWLEDGMENT: Above information supplied by Jim Gurieff, Whiteline Automotive.

"Hi Sam - fitted the anti lift kit, as well as the sway bar links - WOW!!! What a difference - car feels much more solid - you guys (as always) were right!"
-adam

Anti Lift Castor Kits