adj 4 link...why????

[ke70kid]

why do ppl run adj 4link,what are the pros and cons of this mod????

[timbo]

my understanding is they are used for adjusting the pinion angle which is the angle of the differential. when you lower a car alot of geometry is put out including pinion angle so adjustable trailing arms are used to correct this; you want the tail shaft and differential to be aligned horizontally in a straight line. personally im running adjustable upper trailing arms and aftermarket non-adjustable bottoms and i think some people on here do the same.

pros: more adjustment for aligning the diff

cons: not sure as i don't know the full ins and outs but someone will!

[Dom86]

Yep, that is correct Timbo.
The benefit of using them is you get more traction and feel from the rear end.
You are better off with both top and bottom adjustable so you can adjust them together.

[ke70dave]

this is assuming that you know what you are doing when you are adjusting them.

you can also do alot of bad with them as well.

i personally dont understand much about it. but its to do with "anti squat" and...."pro-squat" (or anti-anti-squat hehe) which has to do with how the rear suspension reacts when putting the power down. its very important for drag racing, as the race is either won or lost in the first second of the race.

here is a pretty neat article, i had a quick read seems to be pretty good.

[blair]

Pros: If you run your car low, need to try and point the nose of the diff down to avoid slapping the floor! (or just cut a hole if your that way inclined)

Cons: almost all adjustable 4 links come with rosejoints -> although very stiff, if you actually drive your car hard alot be prepared to buy new ones again and again!

Way around it -> make your own with polyurethane bushes

[sundee]

i feel that just having the upper arms adj, you can just correct pinion angle, but having both upper and lower adjustable you can tune how much "squat" and "anti squat" the car has
im not really clued right up on the topic to give you a tech description but its used heaps in racing, lots in drag racing, i think the more squat you have the more traction you gain.. or something like that.
and you have options of busings, rubber, nolthane, rose joints - (from softest to stiffest)
the stiffer the bushing the greater the feedback to the driver

[FAST EDDIE]

i put upper adj arms in froma dvise for a fairly well known drifter and it did a whole lot of fuck all!!!!!

[Evocom]

I am unsure on the whole "pro/anti squat" deal, can sort of understand the pinion angle thing and I plan on putting them on my track car for none of the above reasons. I am doing it because I have a 31 skyline diff in my KE and the mounts haven't been welded in the perfect spot so my back end can not be aligned with properly with the front.

[Skylar]

The length of the arm directly does not affect the anti-squat geometry. In changing the length of the arms (and changing pinion angle) you move the pivot points on the diff side of the arms. This changes the angle of the arms. The imaginary lines drawn by the trailing arms determines how much anti-squat you're running along with CG height, CG location front to rear and rear tire contact patch location.

As far as I understand, anti-squat is a sort of mechanical binding caused by acceleration/deceleration forces. It determines how much of the acceleration force is absorbed by the rear springs (in case of RWD car) or how much is fed into the chassis. If I remember right, 100% anti-squat means the rear springs don't get compressed at all as you accelerate and all the force is absorbed by the metal of the chassis. The further you go away from 100% anti-squat means the springs are doing more work in holding the rear of the car up as you slam the throttle into the firewall and the car will squat.

What all that means to traction, I don't know. I tend to find that guys decrease anti-squat to get more drive out of the car while drifting. What puzzles me is why we fit traction brackets to increase anti-squat. All this is off the top of my head and been a while since I was looking at doing stuff to suspension so some of it is probably not right.

[H8CHIR6KU]

pretty sure the main reason is too set the pinion angle of the diff. i do find that having the rosejoints in itself was worth the change. the feedback from the back end of the car is awesome compared to the bushes i had origanlly. i wouldnt use it on the street though, way too hard.

anti-squat is another thing all together but you will need adjustable arms to set up