Anti-lift Kit FAQ :
Term usage: "Anti-lift kits" go by several names, among them are Anti-lift kit, ALK, Anti lift, P.S.R.S., transverse link bushings, and possibly a few others. Anti-lift kit or ALK is the common and incorrect term that lumps all of these products under the same term. For the sake of continuity, this post will refer to all of these as Anti-lift kit or ALK.
What are ALK upgrades? The come in either two forms:
a. stiffer bushings alone. (smallest upgrade) Though these aren't traditionally associated with the term ALK, they are a similar upgrade worthy of mention as they are closely associated.
b. stiffer bushings accompanied by redesigned and remanufactured housings. (largest upgrade) Basically these replace the bushing that holds the transverse link (AKA the control arm) and the entire mounting bracket with redesigned and relocated bracket.
Who manufactures ALKs?
Perrin Positive Steering Response System (P.S.R.S.)
Whiteline Anti-Lift Kit (ALK)
GT Spec Antilift Kit
STi Transverse Link Bushings*
STi Group N Transverse Link Bushings*
Whiteline KCA375 offset Transverse Link bushings
*Though listed seperately, both "versions" of the STi tranverse link bushings are identical as they share the same part number.
What do ALKs do? One can separate them into the two varieties for better explanation:
a. The STi/STi Group N bushings are firmer versions of the stock bushings. The possibility exists that these two bushings may be identical though no one has confirmed this either way. They utilize the factory transverse link bushing mounts and will prove better toe control at speed/braking and crisper turn-in. They can additionaly transmit a increased amount of noise, vibration, and harshness (NVH) into the passenger compartment. They are considered a small upgrade. They are designed to increase steering response and better turn-in characteristics.
b. Whiteline's KCA375 offset Transverse Link bushings are firmer versions of the stock bushings and also contain an offset fitment designed to change the suspension geometry by adding additional positive caster. They utilize the factory transverse link bushing mounts and will prove better toe control at speed/braking and crisper turn-in. They can additionaly transmit a increased amount of noise, vibration, and harshness (NVH) into the passenger compartment. They are considered a small upgrade. They are designed to increase steering response and better turn-in characteristics.
c. Whiteline's, Perrin's, and GT Spec's offerings are firmer versions of the stock bushings and also replace the stock factory transverse link bushing mounts with redesigned units that will prove better toe control at speed/braking and crisper turn-in as well as change the suspension geometry by adding additional positive caster. They can additionaly transmit a increased amount of noise, vibration, and harshness (NVH) into the passenger compartment. They are considered a large upgrade. They are designed to increase steering response and better turn-in characteristics.
How do the large upgrade units (Whiteline, Perrin, & GT Spec) work?
Layman's Explanation
They relocate the transverse link mount by varying degrees (depending on manufacturer specs) changing the car's OEM suspension alignment by adding additional positive caster. To imagine the physical working of this technical change, please consider the following analogy: Imagine you are arm wrestling someone using a straight arm. You have an equal chance of winning if you keep a straight arm. Now imagine you are arm wrestling someone with their hand bent at the wrist. This transmits your straight arm force from one direction to two directions, straight down and a sweeping motion towards the table. This is the exact way the large upgrade units work. When braking or accelerating, they change the suspension angle so that some of the force is diverted not through the springs, but through the car's inherent chassis stiffness. This diversion amounts to an increased amount of the front end lift during acceleration and increased amount of front end dive during braking.
These changes allow a pressure change on the contact patch of the front tires during acceleration and braking. This pressure change is actually beneficial and evens out the suspension better allowing for better and faster steering, especially into and out of cornering. Though a bad example, some have even likened it to a poor man's front LSD based upon the way it improves front grip.
Technical Explanation
They change the suspension geometry of your front end by lowering the aft control arm bushings by varying amounts (depends on the manufacturer) increasing caster by varying degrees (depends on the manufacturer) of extra static caster. They change the front pitch and caster geometry by relocating the rear pivot point of the front lower control arm both in the vertical and horizontal plane. The suspension reconfiguration combines to provide the following benefits:
1. Stiffer bushings gives a more solid mounting point for the suspension which does a few things most important of which are better toe control at speed/braking and crisper turn-in.
2. Extra caster which gives a stronger on-center feel to the steering as well as more "dynamic camber" during cornering.
3. Remove the anti-lift and anti-dive characteristics of the stock suspension. What this means is that it effectively softens your front suspension's movement which allows the wheel to follow the road a little better during acceleration/braking in a corner.
What do the terms anti-lift and anti-dive mean? These terms are very, very confusing as most readers can get confused over the apparent double negative connotation of the terms.
Anti-lift is your car's natural ability to absorb lifting forces. This means a car with 100% anti-lift during hard acceleration would exhibit no force transfer to the springs of the car. Stated another way, 100% of the lifting caused by acceleration would be absorbed by the chassis, not the springs.
Anti-dive is your car's natural ability to absorb diving forces. This means a car with 100% anti-dive during hard braking would exhibit no force transfer to the springs of the car. Stated another way, 100% of the diving caused by braking would be absorbed by the chassis, not the springs.
How are these terms applicable to large upgrade units (Whiteline, Perrin, & GT Spec)? These kits, to varying degrees, decrease your car's natural anti-lift and anti-dive characteristics. This will soften the front suspension during acceleration and braking and a softer suspension will even out the load on the front tires, giving a higher total total cornering load available or more front end grip. Another way of looking at this is that under acceleration or braking, the effective spring stiffness is lower, reducing the front end anti-roll resistance, hence reducing weight transfer at the front and less understeer.
Who is a good candidate for this type of suspension modification? Nearly everyone. This modification is an extremely popular suspension upgrade and one that most users truly feel and can experience as opposed to some suspension upgrades that seem to perform better.
How would this effect me in terms of autocross classing? Consult your rulebook for further details. Generally speaking, the large upgrade units (Whiteline, Perrin, & GT Spec) are NOT legal except for the most extreme categories. They are not even allowed in Street Modified. The smaller upgrade units (STi, STi Group N, and Whiteline KCA375 offset Transverse Link bushings) are allowed.
How can I compare the current ALKs? It is probably best to refer to the manufacturer's websites to obtain the best information, though the following can be consider highlights based on current information:
Whiteline's Anti-Lift Kit (ALK):
a. Made of aircraft grade 7075 aluminum.
b. Available in three different bushing ratings. The urethane bushings are identical in physical dimensions, however the 'Duro' or hardness of the bushes is what differs. The comfort version is the softest of the bushings with a duro rating of 70D (Yellow in color with number 70 stamped on face), but still firmer than OEM bushings. The standard version is harder with a rating of 80D (Yellow in color), and the race version has a rating of 90D (Black in color), which is extremely hard.
c. Changes the suspension geometry of your front end by lowering the aft control arm bushings by 20mm increasing approximately 0.5 deg of extra static caster.
Perrin's (P.S.R.S.):
a. Made of extruded 6061 aluminum.
b. Uses Teflon lined, spherical metal bearings (bushings) eliminating any possibility of deflection seen by the stock factory mounts.
c. Changes the suspension geometry by the following specifications:
WRX Wagon gets approximately 3.75 degrees of caster.
WRX Sedan gets approximately 4.2 degrees of caster.
STi gets approximately 5 degrees of caster.
The differences are because of the control arms. If you have a WRX with STI control arms you will have the 5 degrees.
GT Spec Antilift Kit:
a. Made of aircraft grade 7075 aluminum.
b. Uses a rubber bushing which is much stiffer than the softer factory rubber ones.
c. Adds .35 degrees of caster.
Can you compare one manufacturer to another? Not totally, but there are a few points:
a. Bushing firmness can be compared via this flow diagram: Stock --> Whiteline Comfort --> GroupN --> Whiteline Sport --> Whiteline Race. One would hypothesize that the STi transverse link bushing would fall in a similar firmness rating of the Whiteline Comfort as they are an upgrade to the stock bushings, that is if they are in fact different than the GroupN version ones. One could also hypothesize that the Perrin P.S.R.S. with it's metal bushings would provide the highest level of firmness.
How do I install ALKs? Refer to the manufacturer's instructions. For transverse link upgrades without instructions, below are links to some of the better known installation instructions:
.pdf of STi/STi Group N Transverse link installation instructions (.pdf)
Whiteline ALK installation instructions (.pdf)
Whiteline KCA375 offset Transverse Link bushings instructions (.pdf)
When I install these, will I need an alignment after wards? Yes. In addition, you may consider this post regarding toe settings when utilizing Whiteline's ALK.
What is the biggest drawback to this type of modification? The increase in noise, vibration, and harshness (NVH). Generally speaking, the more firm the bushing, more NVH you will experience. The two types to specifically research thoroughly prior to purchasing in this regard are the Perrin's (P.S.R.S.) and Whiteline's Sport Version ALK.
Where can I learn more about this type of modification? You can research specific parts via the NASIOC search feature. Not to discredit the other manufacturers, but Whiteline, their Vendors, and magazines featuring their product have stellar documentation that may provide supporting data for this type of modification.
MRT article
Whileline ALK Discussion Paper (.pdf)
Whileline ALK Discussion Paper (.pdf)
Autospeed article
Autospeed article (.pdf)
Hot 4 article
Rallysport article
Editors Note
This post was created because I wasn't able to find a good ALK FAQ. I came up with the text based on LOTS of searching here. It was also created to be intentionally brand neutral so that it serves as a stepping stone for further research. Upon reading this you should have an idea of what type of ALK best suits your needs. The manufacturer is up to you.
If you find an error in this FAQ, please PM me with factual details and I will update this post. Responses such as, "I have XXX's ALK and it's great!" or "XXX's ALK broke after 1 month" are not appreciated here, that is what the Car Parts Review Forum is for.
source:
http://forums.nasioc.com/forums/showthr ... ?p=8384387
je me cherche des USDM justement à bon prix. le marché est envahi de JDM 