Anti lift kit... p.s.r.s. ... Group N Control Arm Bushings

[kevinG]

this part... http://i71.photobucket.com/albums/i160/r33owner/alk.jpg


many companies make these all for different prices...

my question is for the guys that run these on the dirt... does it make a big difference on the dirt? i know every one that runs these say they are a must for time attack type but i have not heard of them on the dirt...

[UP2MTNS]

I'd be curious to know too....not that I feel I need to upgrade it, but at 90K miles, I assume my bushings need to get replaced so I might as well upgrade. But other than pushing your front tire up a little more (that's what positive caster does, right? or is it vise versa?) I'm not sure of the benefits on dirty dirty dirt dirt.

[kevinG]

yep it pushes it up more... which should keep you in line better at speeds... and it allows you to use less toe, which will give you a bigger tread profile while going straight... and due to angles it will also increase you tread profile while turning too!

and on launches it will help keep the nose of the car down...

i cant see anything bad about this part but i just dont know about on dirt... i guess i am just gonna get the group-n ones for $90 or so and find out...

[ProjectBomber]

check your rule book!!! i know in many scca auto-x classes you cannot use these because they modify the suspension pickup points (considered chassis modification) just fyi if you plan to do any competitive rally-x

[kevinG]

already have a new turbo and coilovers... iirc those already destroy my classes.

[ten80]

The Group N version adds no caster and has the same geometry as the stock control arm bushing, but with stiffer rubber. I have these and they greatly increased turn-in feel and improved tracking.

Perrin PRSS, Whiteline ALK, etc add caster and change suspension geometry.
I've only heard good things about the added caster and resulting handling. However, some models have really stiff urethane (rather than rubber, like OEM) and add a lot of NVH, so be certain to buy the ones to fit your needs. Whiteline makes a softer "sport" version and one or two brands have Group-N style rubber.

[JacksonRally]

I don't do anything "anti" in the dirt. "anti" is short for mechanical bindage of the suspension. On a road course or the street this is something to tune into your suspension but for the dirt you just want the suspension to move freely and let the valving in your shocks/struts do the work. Your best bet is to go with a much stiffer bushing and leave the geometry alone.

[UP2MTNS]

I don't do anything "anti" in the dirt. "anti" is short for mechanical bindage of the suspension. On a road course or the street this is something to tune into your suspension but for the dirt you just want the suspension to move freely and let the valving in your shocks/struts do the work. Your best bet is to go with a much stiffer bushing and leave the geometry alone.

^^you know I agree with you, but I thought you said the custom control arms you did last year increased your castor? (yes/no? I could easily be mistaken)

'anti-lift kit' is just a marketing term, technically its not really restricting anything.

[lorenkb]

There seems to be a lot of misconception when it comes to anti-lift

I don't know the specifics of all the kits sold, but the Whiteline kit in particular is a good example. People seem to think the anti-lift kit will keep the nose down under acceleration, and this is NOT true. Both anti-lift and anti-dive are decreased when the kit is installed. Your front end will rise more under acceleration, and dive more under braking.

If anything, the Whiteline kit should be called the anti-anti-lift kit ;)

[UP2MTNS]

There seems to be a lot of misconception when it comes to anti-lift

I don't know the specifics of all the kits sold, but the Whiteline kit in particular is a good example. People seem to think the anti-lift kit will keep the nose down under acceleration, and this is NOT true. Both anti-lift and anti-dive are decreased when the kit is installed. Your front end will rise more under acceleration, and dive more under braking.

If anything, the Whiteline kit should be called the anti-anti-lift kit ;)

uhhhh.....not according to perrin:

The Perrin Postive Steering Response Kit (PSRS) is an anti-lift kit (ALK) designed to prevent lift under acceleration in cornering.


HOW IT WORKS: The PSRS relocates the rear mount of the front control arm, increasing the caster angle for better turn-in and response. This design will also control wandering from uneven pavement or larger wheels and tires.
Perrin has recently redesigned the kit to use Delrin bushings for zero deflection and elimination of noise for trouble-free operation. The 6061 aluminium housing makes for a strong, precise part. A 10-15% increase in noise, vibration, and harshness should be expected as the stiff mounts absorb less road noise.

But that's just marketing, so lets think about it.

whenever I can't really visualize what small changed will do for a vehicle/forces, etc....I imagine the extremes:

so, by changing the castor, you're really changing where the engine sits over your wheels. (more castor....engine weight is farther behind, less castor, engine weight is farther forward).

in the extreme, if we moved the engine way forward (and the wheels back....negative castor)......while braking, the engine weight would have more leverage around the focal point (where the wheels hit the ground) and would push the car farther forward/down. the opposite would be true on accelerating, and the engine would tend to lift more.

so, in the other extreme, if we pushed the engine weight wayyy back, like a mid engine car......the engine weight would have much less leverage to push the front end of the car back or forward on acceleration and braking.

another way to think of it.....stand on your bumper and bounce. then stand on your roof and bounce. Where is the most deflection? By moving the engine weight back, you're distributing the weight better on all 4 corners and, so less deflection all around, on braking and acceleration.


Of course, <soap box ON>, this is part of your suspension, and your entire suspension is a SYSTEM. so this will depend on other things as well....doesn't matter what you do up front, if your rear shocks/springs are shot, your front end is going to lift on acceleration (as your rear dips) no matter what ALK you have. <soap box OFF>

[kevinG]

great post... anyone with these have a personal review on this subject?

[lorenkb]

uhhhh.....not according to perrin:



But that's just marketing, so lets think about it.

whenever I can't really visualize what small changed will do for a vehicle/forces, etc....I imagine the extremes:

so, by changing the castor, you're really changing where the engine sits over your wheels. (more castor....engine weight is farther behind, less castor, engine weight is farther forward).

in the extreme, if we moved the engine way forward (and the wheels back....negative castor)......while braking, the engine weight would have more leverage around the focal point (where the wheels hit the ground) and would push the car farther forward/down. the opposite would be true on accelerating, and the engine would tend to lift more.

so, in the other extreme, if we pushed the engine weight wayyy back, like a mid engine car......the engine weight would have much less leverage to push the front end of the car back or forward on acceleration and braking.

another way to think of it.....stand on your bumper and bounce. then stand on your roof and bounce. Where is the most deflection? By moving the engine weight back, you're distributing the weight better on all 4 corners and, so less deflection all around, on braking and acceleration.


Of course, <soap box ON>, this is part of your suspension, and your entire suspension is a SYSTEM. so this will depend on other things as well....doesn't matter what you do up front, if your rear shocks/springs are shot, your front end is going to lift on acceleration (as your rear dips) no matter what ALK you have. <soap box OFF>

Perrin needs to stop letting marketing write their product specs then. The kit moves the rear LCA mount down and outwards. The outwards is what adds the caster. The downwards movement is what is primarily responsible for the new anti-lift characteristics. If I understand our suspension correctly the addition of caster also has a slight affect on anti-lift as well because it affects the angle at which our struts sit (is this right or am I crazy?)

Whiteline actually has a nice little document (http://www.whiteline.com.au/articles/Effect%20of%20WL%20ALK_b.pdf) on what's going on.

There was a very informative thread on this over at Nastysock... I'll see if I can find it.

[UP2MTNS]

OH....I know what you're talking about, we're both kind of right and king of wrong:

from your WhiteLine document:
In the case of the Subaru WRX fitted with the ALK, the suspension system becomes
softer during braking and accelerating actions, as both anti-dive and anti-lift have been
reduced. A softer suspension will give rise to larger deflections.what I THINK they're saying is, with the stock WRX, the suspension is pretty soft....so when you add the ALK, which stiffens up the suspension mounting point (and much stiffer bushing) and changes the geometry, so now more forced are placed upon the now very undersprung springs/struts (see? everything is a SYSTEM!) and therefore, under hard acceleration/braking, you get more suspension deflection, and thus, more dipping/lifting.

In other words....when you change (in this case, stiffen) one part of the system, it throws off the balance with the rest of the system, so you really need to get a stiffer strut/spring set up to properly take advantage of an ALK system.

Loren....nice find, this makes a lot of sense to me now.

[lorenkb]

Not quite Jon. Stock, the WRX is setup to take some of the forces during accelerating and braking and transfer them away from the strut/spring. With 100% anti lift and dive your springs would see no more force outside of what is seen at normal ride height.

With the ALK's change in geometry (stiffer bushings are not the issue here) you are reducing both anti lift and dive, so your springs are seeing more force. Your effective spring stiffness is lowered, but this is not a negative impact... in fact the very reason for doing this is to get a lower effective spring stiffness. You are reducing weight transfer between the front two wheels (AKA your anti-roll rate), allowing higher cornering loads. Stiffer struts and springs are definately not needed to see the benifits.

EDIT: Found that nastysock link (http://forums.nasioc.com/forums/showthread.php?t=601718&highlight=n00b+alk), lots of good discussion.

[kevinG]

http://www.mrtrally.com.au/performance/howantilift.htm

[JacksonRally]

To simplify things here is what is happening. If you move the rear pivot on the LCA up or down (IE: no longer parallel with the chassis) this give an anti-dive/lift characteristic. This has nothing to do with castor. Though they are killing 2 birds with one stone here by adding more castor. And yes I did add more castor to my LCA's but I did not change the pivots.

[UP2MTNS]

Not quite Jon. Stock, the WRX is setup to take some of the forces during accelerating and braking and transfer them away from the strut/spring. With 100% anti lift and dive your springs would see no more force outside of what is seen at normal ride height.

With the ALK's change in geometry (stiffer bushings are not the issue here) you are reducing both anti lift and dive, so your springs are seeing more force. Your effective spring stiffness is lowered, but this is not a negative impact... in fact the very reason for doing this is to get a lower effective spring stiffness. You are reducing weight transfer between the front two wheels (AKA your anti-roll rate), allowing higher cornering loads. Stiffer struts and springs are definately not needed to see the benifits.

****, now I'm really confused. I want to believe you...I really do...mainly because I'm sure you're smarter than me, but something doesn't make sense to me. no light bulbs yet.

I need to print this out and take it home, this is too complicated to read at work. LOL

[lorenkb]

That nastysock link has a lot of good info... just ignore the bickering towards the end :roll:

I'm still not 100% on the whole suspension dynamics thing, but the whiteline doc combined with some of the discussion in that other thread have all the bits and pieces to where it finally starts making sense.

[deadbeatdude]

wow after reading all of this no im just gonna do the group n ones that dont change the geometry just stiffer bushings. if anyone has installed these. are they hard to do. the psrs seems like a whole lot of work for little gain

[JacksonRally]

wow after reading all of this no im just gonna do the group n ones that dont change the geometry just stiffer bushings. if anyone has installed these. are they hard to do. the psrs seems like a whole lot of work for little gain


Always worth it for stiffer bushings. I think the only pain is gonna be removing the factory bushings...might have to burn them out!

[Drew84]

I had a set I wanted to run but they where not legal for my auto-x class.

[ten80]

The group N rear control arm bushings are already pressed into metal housings, like the PRSS. However, the group N bushings don't add any caster. If you want to keep the stock housing, you can also use Whiteline KCA375 bushing that presses into the stock aluminum housing. They are SCCA legal and add 0.5 caster without needing subframe spacers, a major pitfall of GT-Spec, Perrin PRSS, and Whiteline ALK kits if you value ground clearance.

That said, I have the group N rear control arm bushings and LOVE them. Steering is more precise and turn in a tad more crisp. NVH is acceptable and no more than if using Group N tophats.

[Draco-REX]

****, now I'm really confused. I want to believe you...I really do...mainly because I'm sure you're smarter than me, but something doesn't make sense to me. no light bulbs yet.

I need to print this out and take it home, this is too complicated to read at work. LOL
If you have the time and inclination, I highly reccomend "Tune to Win" and "How to make your car handle." Both are excellent books on suspension theory and design.

Essentially, by having the control arm at an angle to the ground, you can use braking and engine torque to stiffen or soften the effective spring rate. The ALK removes this and lets the suspension concentrate on maintaining grip, to put it simply.

A friend of mine just put the GTSpec ALKs on his RS wagon. His first comment was that the car handled more like a RWD car. TOday we went for a real shakedown, and he said he has had to adjust his driving style as all the tricks he learned to get the car to rotate now are overkill.

Now I can't wait to install my ALK. :)

[UP2MTNS]

If you have the time and inclination, I highly reccomend "Tune to Win" and "How to make your car handle." Both are excellent books on suspension theory and design.

Essentially, by having the control arm at an angle to the ground, you can use braking and engine torque to stiffen or soften the effective spring rate. The ALK removes this and lets the suspension concentrate on maintaining grip, to put it simply.

A friend of mine just put the GTSpec ALKs on his RS wagon. His first comment was that the car handled more like a RWD car. TOday we went for a real shakedown, and he said he has had to adjust his driving style as all the tricks he learned to get the car to rotate now are overkill.

Now I can't wait to install my ALK. :)

interesting feedback....thanks. hmmm....if ALK = over steer.....and front LSD (upgrade) = oversteer....ALK + front LSD = :headbang: ??? :headbang:

[williaty]

I'm the friend Draco was talking about :D

OK, so the first confusion is the name. The Anti-Lift Kit doesn't add the anti lift properties, it removes the stock anti-lift/anti-dive geometry.

Second, don't ever listen to Perrin's explanation of anything. They sell pretty parts, but they almost never get the theory right. In fact, their "alk" doesn't even fully neutralize the stock anti geometry because it doesn't move the suspension pivot far enough.

Third, in most circumstances, there's nothing horribly wrong with lift or dive (obviously, there's exceptions to this). However, people don't like the way it feels. So the engineers design "anti-" geometry into the suspension. This causes the suspension to move in a particular way in response to longitudinal weight transfer. The net result of this is that the "force" of the weight transfer bypasses the spring and damper and instead runs through the suspension linkages. The effect of this is like having the spring rate shoot through the roof when you have fore/aft weight transfer. In other words, anti geometry makes the suspension very, very stiff any time the car is trying to pitch forwards or backwards.

Installing a properly designed ALK removes the anti geometry and prevents this stiffening of the suspension under pitch. Obviously, as we all know, overly stiff suspensions aren't good for grip on anything other than plate glass. The point of the ALK is to keep the front end in better contact with the road under breaking, acceleration, or bumps that look to the car like pitching (e.g. frost heaves, speed bumps, etc). This gives more front end grip in dynamic situations and allows you to come in harder on the brakes and get on the gas sooner.

Now, as Draco said, I just installed the GT-Spec ALK on my car. I'm going to paste my .sig from another forum into here because it's the quickest way to list my relevant mods:
2005 Impreza 2.5RS Wagon in Regal Blue Pearl
Basic Suspension: USDM STi Springs, Tokico D-Specs, PolTec Spherical Bearing Endlinks, Whiteline 22mm Adjustable RSB, Whiteline Quick Release Rear STB, GT-Spec ALK
Bushings: Full STi Group N Lateral Link, Trailing Link, and Strut Mount Set, Kartboy Tranny Crossmember, TiC Comfort Rear Diff, Whiteline Steering Rack
Competition: Primitive Racing 3/16ths Front Skidplate and Rear Diff Protector, Alfa Club Rally Odometer/Chronometer
Powertrain: Stromung Stainless Steel 2.25" Midpipe, DIY Ghetto-rific Catch Can, Group A Performance Lightweight Crank Pulley, Hybrid Silentake, RomRaided
Electronics: Hawker Odyssey PC-680MJT Battery, Hella Rallye 1000 FF Driving Lights, Rear Deck Light Addition, Map Light Addition, Hella Supertones
Rolly Bits: Summer-16" OEM wheels in Falken FK452s | Winter-16" OEM Wheels in Hankook Icebear W300s
Body: Front Grille Center Pillar Delete, DIY Big Assed d@mn Serious Rally Style Mudflaps, Obsessive Amounts of RAAMmat and Ensolite, Polyurethane front lip
ICE: Pioneer DEH-3900MP, Pioneer CD-IB100II iPod Controller, Pioneer TS-D161R 6-1/2" Kevlar 2-Ways
Interior: DIY Hypoallergenic Cabin Air Filter, GC-Lock, S204ed Center ConsoleOK, so prior to the ALK, with all the other suspension work, the car was still just to the pushy side of neutral. If I came in well under control and did everything right, the car wouldn't wash wide, but I had to be gentle and wait to get on the gas. Coming into very tight, very slow corners, I had to come in on the brakes while turning in to get the car to roll hard to the outside and "trip" over the front outside wheel, initiating rotation. Lifting out of the throttle was not enough to initiate rotation and adding power only made the car wash wide. On very low grip surfaces, the car was a pain to drive. Initiating rotation was almost impossible. To turn on snow, I had to goose-release-goose the throttle which resulted in rotation, but also resulted in pushing 10-15 feet wide. Obviously not a realistic thing to do on the road in an emergency. While I never managed to get into trouble with this car like I had with my previous one (89 4Runner with TRD suspension), I've always had the feeling that if my Subie got away from me, it wouldn't be savable (unlike the 4Runner. Yes, I'm saying it had better handling balance than my Subie even with all the suspension work). That being said, over the last 4 years, I have developed many techniques and habits to drive around the inherent understeer in the Subie.

Then I put the ALK on. I did it on a day of snow and freezing rain, right before a local Subie club meet. I got the car done in time to drive it to the meet. I pulled the car out onto the slick driveway and 3 point turned it to face the road. As I put it into 1st and turned towards the road, I was shocked to have the rear end go sideways from a standing start. I though it was a fluke. Then I pulled onto the road, and again had the rear end slip while the front end gripped (of course, I watched Draco in the rear view mirror slide sideways anime-style across three lanes of road :lol:). I decided I had better be careful with the "new" car and pulled into a multi-level parking lot near my house. I played with the car a bit and was delighted to find I could now steer from the rear with my right foot. Leaving the parking lot, there was a steeply uphill very long tight hairpin left. I was actually able to keep the nose pointed at the center of the turn and slide the car sideways up the whole hairpin like you see the WRC guys do. It was awesome! Fast forward a few days and I take the car out on a shakedown tour to help become used to the new handling. Multiple times that day, I was surprised to find myself in 4 wheel drifts on tarmac where the car was still steerable, no washing to the outside. I also almost spun the car on 2 occasions when something I used to have to do to force the car to turn at all now induced snap oversteer. I'm actually thinking of softening my rear sway until I get used to it.

Wow, that was long winded! A short summation would be that before, if the car were sliding and I'd goosed the gas, the car would rotate some, but it would MUCH MUCH more just push for the outside of the turn. Now, the car rotates like a mofo and mumbles about how it could wash outside if it wanted to and I better give it back its stapler or else, but it never follows through on the threat.

[boydfoose]

wow those are really nice
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