4 link adjustment

[bigm]

Hey guys,
This is more out of interest but i was wondering changing lengths of the 4 arms affects the cars performance? IE traction and others.
also is their any advantage of inceasing the wheel base by lengenthing all 4 arms?
any info anyone has would be great.
o and more interested in drifting if that makes a difference
cheers

[Clinton]

making a longer wheel base would make it handle a little better i guess. but then nothing else lines up? and probs not even worth the effort for the minimal upgrade in handling

[marvis]

If you were going to do that you could always throw an IRS rear end in..

[Javal]

making a longer wheel base would make it handle a little better i guess. but then nothing else lines up? and probs not even worth the effort for the minimal upgrade in handling

Pinion angle is another reason people put in adjustable trailing arms.

When you lower your car, your diff nose no longer sits in the correct position (points down), thus moving some point of peak force or some shit... someone explain this better....

Basically when you're diff nose is sitting level, you win the prize, less wheel hop, more power down etc. So you put in adjustable upper trailing arms to adjust the pinion angle without affecting wheelbase, or upper and lower to rectify pinion angle AND adjust wheelbase if that is your desire.

[shichi~]

yep as javal said set your pinon angle straight with the tail shaft should be a good start
then i guess u can fuck around with it after drifting testing out different settings

when i had mine in i noticed that the car was alot more controllable at high speed drifts felt alot more stable

but now im goin to run stock arms with new bushings as it very harsh with a locker and feels like your diff is goin 2 fall off lol id say it not suited to a car u drive daily

[bigm]

thanks guys,
it was just a thought about the wheel base
will definatly adjust the pinion angle.

anyone know anymore about this point of peak force?

and marvis i aint bloddy putting IRS in the peice of shit

[Simon-KE70]

i've played around with settings on my old blue car and i basically made the lower arms the same length as stock and the upper arms 15mm longer, this moved the pinion back into the level postion and then some... so really it was facing up a tad, so when the susp compressions is back into the level postion, this is where the extra grip is from i guess.

i found it was very smooth to drive after that you could really throw it hard into high speed corners and if you were going a tad hot you could regulate the throttle and it could come back into line no worries.

[Javal]

thanks guys,
it was just a thought about the wheel base
will definatly adjust the pinion angle.

anyone know anymore about this point of peak force?

and marvis i aint bloddy putting IRS in the peice of shit

I had the concept loosely explained to me a few years back... i can't recall most of it though :S

Basically the conclusion was to sit your diff level for winning styles, if not a titch nose up. If you get the adjustable arms, do some experimentation and report back!

[RobertoX]

re pinion angles...
You want to set it up so that the 2 universal joints (front and rear) are at the same angle under load.
This means that when the car is squatting and the suspension arms are all loaded up (eg bushes deforming etc) then the joints are working at the same angle to prevent tramp.
(ever notice how the 2 uni joints are out of phase by 45 degrees? ;) )

In an ideal situation, when you least want tramp the uni joints should be both straight.

So to set it up you line them up so that the diff nose points up slightly from where you want it so that when when it is loaded (ie you are accelerating) it moves down. The easiest way to determine where it should be angled is through tuning, this means you get it roughly in the right position, test it, adjust it to a better position and test again... iterate until you are happy.

A good base is to use the same angles as factory, however with stiffer suspension the car will squat less and with rose joints the bushes will deform less therefore you want less difference in angle than factory.
On the other hand you might be getting more traction, so the car will squat more.
You also might have lowered your car, so your anti squat will be less meaning the car will squat more (in the case of 80's toyota geometry anyway).




As far as increasing the wheelbase goes.
Very generally speaking a longer wheelbase means a more stable vehicle, a shorter wheelbase means a less stable vehicle (twitchy).
Another way of saying exactly the same thing is that a longer wheelbase means a less responsive vehicle and a shorter wheelbase means a more responsive vehicle.
Which one means "good handling"? Who the hell knows... try it and see.

[aaron]

i am curious why people on here believe the 'unloaded' pinion angle should be set upwards slightly, because alot of info i am finding on the net says to set it downwards??
eg.
http://www.baselinesuspensions.com/info/pinionangle.htm
http://www.carcraft.com/howto/91758/index.html

help please?

[--Redwork--]

Aaron...I was under the impression you should set it down a coupl of deggre too...
But up thinking about it i can understand the idea...

With the pinion angled slightly up.. as the car squats (get lower) yje diff will rotate forward because of the top trailing arms being shorter than the bottom ones hence, scribing a shorter arc and pulling the top of the diff over..

Now.. with an equall length trailing arm you don;t get the diff tilt.. Only a difference in the angle if the tail shaft, As the duff travels up the front of the tail shaft stays fixed..
So in theory if your diff travlled far enough you could set it at 2 degree down and at full drop end up with it 2 degrees up...

This all how ever relates in no way to us due to the fact 99% of us run super stiff springs and would be lucky if our diff moved up anymore than 40mm from a static height..

One thing I haven't touched on is deflection...
Say for instance you had no suspension travel at all. Was 100% solid.. You would using the theories explained above set your pinion angle pefectly straight.. yes.??

WRONG!!!!...

Whether your running stock bushed urethan ones or rose joints, you will still have some amount of deflection in the trailing arm bushes. In the case or those running rod ends the defletion will come from the car its self..

So... Me personally.. I would set the pinion angle down just a little reguardless.
But the only way to find the best setup is to experiment with it...


Also note that raising the pinion angle brings the front of the diff up, and you may find if your car is low enough the nose of the diff will hit the floor one occasion..

Perfect example is a freinds car... was supper low. didn't have adjustable trailing arms so the diff was pointing down due to the top arms pulling it over as I explained above..
But nearly ever time he dipped the clutch or smahed threw a gear the diff would twist up and violently smash the floor... Sounded terrible..

Hope that helps...

[RobertoX]

errr... as pointed out by --Redwork-- the following is wrong, sorry:


Depends on which way your tailshaft is spinning, I'm not sure but it might be different between cars.
If it is spinning anticlock wise looking from the rear of the car then your ring gear will need to be on the passengers side and the nose will point down as you load it up (therefore you need the nose pointing slightly up in the static/unloaded position)
If the tailshaft is spinning clockwise when looking from the rear then the ring gear is on the driver's side, the reaction of the nose will be up so the nose has to point down in the unloaded position.

Anybody knows which way the tailshaft spinns in an 80's Toyota? Or what side is the ring gear on?
Also what cars were those links in reference to?

[Mr Fujiwara]

i aimed mine down and it made a filthy noise, a wurring under accel.
my car is very low and i aimed it down when i put the 4link in because orginally the diff nose was hitting the floor, when i set it back close to where it was level the car felt heaps better, i havnt yet had time to work out other good setups, such as aimed up, or even 100% straight in terms of getting links equal links etc.
i was under the impression aimed down gives better propperties for drifting, but i never really did any research.
But the solid mounts seem to give me heaps of traction in any conditions and i would definately say it makes the car more stable. the car is daily driven 2-3 times a week i still dont find it overly uncomfortable.
solid mounts :P

[--Redwork--]

RebertoX..... which way the tail shaft spins has nothin to do with it...

The diff will always twist up under load... T
he only tme a diff will swist down is when you reverse...

[Jonny Rochester]

Depends on which way your tailshaft is spinning, I'm not sure but it might be different between cars.
If it is spinning anticlock wise looking from the rear of the car then your ring gear will need to be on the passengers side and the nose will point down as you load it up (therefore you need the nose pointing slightly up in the static/unloaded position)
If the tailshaft is spinning clockwise when looking from the rear then the ring gear is on the driver's side, the reaction of the nose will be up so the nose has to point down in the unloaded position.

Anybody knows which way the tailshaft spinns in an 80's Toyota? Or what side is the ring gear on?
Also what cars were those links in reference to?


For every engine anyone on this forum is going to play with, the crank spins clockwise when looking from the front. And with all the gearboxes we use, they are such that the tailshaft will spin the same way. And in 4th gear the crank is locked to the tailshaft 1:1. And for every finaldrive anyone on here is using, the crownwheel is on the left side and the pinion is mounted below the centre line, and uses a hypoid gear (to reduce noise).

But knowing this, it makes no difference anyhow to what dirrection the tailshaft spins. When the rear axle is loaded, (driving forwards), the front of the diff housing will want to rise. This is why you set it up to point down a little in static position (in relation to the gearbox output shaft, which often is not horizontal).

Whole books are written about this, and the lengths and angles of a 4 link system. For drag racing, you don't just have 4 equal length arms that are parallel and horizontal, there is much more to it than that.

Thankfully, for most of us that just do casual laps and some drift, it makes little difference.

[--Redwork--]

^^^^^^ Your right about the equal 4 link Jonny...
Was just useing a parrallel setup to help explain the effect enequal length arms have on effecting the angle when under compression...
The stock setup when lowered, has vary substainial effect of the pinion angle under suspension compression due to the top arm being already alot shorter and it on nearly a30 degree angle when car is static...

Seting up a proper drag style 4 link is a fairly tricky process..
Changine the angles of the bars has massive effects on line of force.. Altering whether the car squats or lifts or stays in the same possition..

[RobertoX]

RebertoX..... which way the tail shaft spins has nothin to do with it...

The diff will always twist up under load... T
he only tme a diff will swist down is when you reverse...

Yeah, lol you are absolutely right! That's what I get for posting at 7 in the morning, I'm an idiot :P