KE70 4 link Arm options

[Sprinter Freak]

Hey guys

Am in the the midst of putting the diff back in my ke70, and noticed that the upper diff mounting points have suffered alot of distortion and stress.(broken a few spot welds and a small crack in one of the upper mounting brackets).

I have been running the T3 adjustible 4 link rods for about a year now and ive noticed the rear end of the car has a lot more creaks then it used to. From what i can see, when the car goes over an uneven surface (hill or drive way) the links move to a point then bind up and put all the pressure on the upper diff mounts.

What im wondering is, can i stop this from happening by adjusting the lenths of the 4 links correctly?(currently set to standard length)


Or is that just the characteristics of spherical 4 links?

Have been doing a bit of reading and frak and a few other members on here suggest that, using the standard links with urethane bushes rather then the spherical links.

This sint ideal for the diff pinion angle (points the nose of the diff down towards the road, from what ive read the nose should be 2-4 degress above level) but will put alot less stress on the mounts. But what im wondering is, will the standard links make the car axle tramp when drifting? (the car is a dedicated drift car)

Another option i was looking at was running standard bushed upper links and the spherical lower links so i still have the pinion angle adjustablity. But will this just the transfer the torsional stress to the lower mounting points?

The car is pretty low at the moment chassis rails about 80mm off the ground, but want to get the car lower so will need an arm set up that will work with a very low car. I know that the best solution is to go an equal 4 link set up with the car that low, but funds dont allow that at the moment so need an interum solution.


Let us know what you guys think.


Cheers

Ryan

[Jacobxxx]

Yeah that's pretty much what happens.

My car is lowwww and i just run standard arms and AJPS traction brackets and good shocks, no tramp.

Alternatively if you're set on adjustable arms, whiteline do a bush type adjustable arm for ae86

[Jimmee1990]

If you want the car that low, you will never get good arm angles with unequal length 4 links. As there is no flex in the rose jointed ends all the independant side to side suspension movement is basically the mounts and chassis twisting. There is nothing you can do adjustment wise to prevent this. The best interim solution would be to put the standard top arms back in with rubber or urethane bushes to get some flex back, however your top arm angles will still be terrible at that ride height and promote tramping and overall very poor diff control.

Personally I would raise the car to fix the arm angles so it still drives okay until you can afford to go equal length 4 link, then lower it again after.

[Sprinter Freak]

Yeah that's pretty much what happens.

My car is lowwww and i just run standard arms and AJPS traction brackets and good shocks, no tramp.

Alternatively if you're set on adjustable arms, whiteline do a bush type adjustable arm for ae86

Ah damn, thought that might be the case. Do your springs sit on an angle or flush with the spring seats with the diff tilted forward?

And does the rear driveshaft uni bind up or sit at a funny angle? Yea have seen those but reckon ill just wait till I can go equal 4 link, then change to rose jointed arms bottom and top.

Rose jointed equal 4 links shouldn't bind up like the un equal 4 links yea???

[sundee]

That's just what happen's with the unequal setup period.
Having rise joints just makes it worse because they done have the "give" that rubber bushes do.

It all happens because you have 2 different length arms wanting to travel a different path, technically arc.
Pretty much like having a 3 leg race with your mate, 2 minds, 2 wants and 2 decisions that will take 2 paths.. Ie they fight.

The only way you can get rid of this problem is go equal length, period!

Get a protractor out and a piece of paper, leave the pin in the same point, draw an arc, then increase the length of the protractor and draw another arc..
See how they are both different... That why I mentioned a 3 leg race..you now have 2 different actions, but coupled together by 60kg of steel!
Something has to give, and it's always the weakest link... Spot welds on the chassis near the mounting points.

[Sprinter Freak]

If you want the car that low, you will never get good arm angles with unequal length 4 links. As there is no flex in the rose jointed ends all the independant side to side suspension movement is basically the mounts and chassis twisting. There is nothing you can do adjustment wise to prevent this. The best interim solution would be to put the standard top arms back in with rubber or urethane bushes to get some flex back, however your top arm angles will still be terrible at that ride height and promote tramping and overall very poor diff control.

Personally I would raise the car to fix the arm angles so it still drives okay until you can afford to go equal length 4 link, then lower it again after.

Ah k fair enough, will swap out the top arms for the standard ones so it flexes a bit more,. Yea the top arm angles will be bad, but I should be able to correct the pinion angle with the adjustible lower arms. Which should stop driveline the shudder and keep the uni joints at a better angle. That should do for the moment. Will also try raising it if it gets too much tramp with the new upper arms.

[Matt]

what gearbox xmember u running ae86 or ke70?

[Sprinter Freak]

That's just what happen's with the unequal setup period.
Having rise joints just makes it worse because they done have the "give" that rubber bushes do.

It all happens because you have 2 different length arms wanting to travel a different path, technically arc.
Pretty much like having a 3 leg race with your mate, 2 minds, 2 wants and 2 decisions that will take 2 paths.. Ie they fight.

The only way you can get rid of this problem is go equal length, period!

Get a protractor out and a piece of paper, leave the pin in the same point, draw an arc, then increase the length of the protractor and draw another arc..
See how they are both different... That why I mentioned a 3 leg race..you now have 2 different actions, but coupled together by 60kg of steel!
Something has to give, and it's always the weakest link... Spot welds on the chassis near the mounting points.

yea i know what you mean, have been reading up about how the upper and lower arms run on different arc's, therefore work against each other. Didn't know that going rose joint isn't alway better when i bought the T3 links. Going an Equal 4 link is definitely on the cards soon, just need to get something in that will work before raleigh in april.


what gearbox xmember u running ae86 or ke70?

I'm using an Ae86 gearbox crossmember

[drift kid]

I have done equal length 4 link and run standard style trailing arms with nolathane bushes and I have dropped the mount on the lower on the diff to make the angle level, I highly recommend using a urethane bush over a spherical bearing

[Sprinter Freak]

I have done equal length 4 link and run standard style trailing arms with nolathane bushes and I have dropped the mount on the lower on the diff to make the angle level, I highly recommend using a urethane bush over a spherical bearing

Even in an equal 4 link set up? i thought it was fine to run spherical joints, as they won't bind with all the trailing arms moving on the same arc?

I know their harsh but its a track car, don't mind the harshness. Only reason i could think you wouldn't run them with an equal four link is if they would impede the suspension travel or damage the car.

[sundee]

If your go equal length use rose joints.

Ps - I would be leaving the lower arms stock (these set your wheel base) and run adj upper arms to correct the pinion angle.

[Jimmee1990]

Definitely use rose joints if you go equal length, and different bolt positions on the boxes so you can play around with squat and anti-squat by changing the arm angles.

[drift kid]

To be honest I don't agree with that, urethane bushes are perfectly fine, they are stiffer than a stock rubber bush but not as harsh and damaging as a rose joint, yes it is a track car but why make something harsh and unenjoyable when it isn't nessiscary, I really enjoy the comfort that my car has on the track

[sundee]

If its got a gutted interior, then having rose joints (increasing NHV or NVH) will be neither here not there.
it does increase the road transmitted noises, but, you have a helmet on... it doesnt add clunking or anything link that... its more like just turning up the ambient noise.

the rose joint gives you the most direct link between the driver and the road.
ive ran them in street cars and it hardy makes a difference in noise, but maybe im just deaf..

thats why serious race cars run nothing else..

[drift kid]

I'm not talking about noise, I'm talking about bumps and shudders from driving over rough surfaces/undesirable objects etc, it transfers the abuse straight into the chassis stretching bolt holes and cracking welds etc, high end motorsports can afford a new chassis etc, I would like to make my car last as long as I can

[Jacobxxx]

I plan on crashing mine before it wears out.

[sundee]

Right on man! Hahah

[Jimmee1990]

With an equal length setup there shouldn't be any massive load on the arms or mounts though, as they are there to pivot only and there's no bind or twist acting on them either. The shocks and springs would take almost all of the force from road imperfections.

[sundee]

you would get pulling when you yanked the old handbrake and some push when you kicked the clutch... but really.....
F it, just run them in an equal length, happy dayz haha

[drift kid]

There is definitely much load on these, that is what these arms do, they are designed to stop the diff from moving forwards and backwards and at the same time they allow it to move up/down, I don't see how a shock is going to stop the load of the rear wheels hitting a sudden incline (ripple strip edge) the forces will be transferred straight through the arms, through the rose joints and into the holes/brackets/welds that the arms are bolted to, I am not saying that rose joints are stupud or a bad idea, I am just saying that there is much that is overlooked when people do this sort of modification

[Skylar]

I remember fixeruperer and a few guys on toymods had issues with ovaling out the holes that the lower 4 link arms attached to. I don't remember if they had solid links but that's something to think about too.

I personally prefer at least one bushed end. I just put harder bushes in my standard arms since I'm too cheap to buy whiteline arms or half/half arms from the likes of Battle version or Cusco. Let's face it, we aren't racing in some competitive series like IPRA or ADGP nor are we going for world record lap times like bazda. Just trying to keep the car nice enough to drive and have fun in and together enough so it lasts through several track days without something breaking. and so, is that stuff absolutley necessary to blow your money on?

[drift kid]

I agree

[AJPS]

I run half bush half rose joint in the rear of my car as class rules stipulate no rear firewall mods can be done (no equal length)

Maybe on circuits and on cars with IRS complete rose jointing is the best option

but with an unequal 4 link, the binding in the top left with all rose joints is terrible, a lot of mid corner speed can be picked up with bush end (at least of hillclimb/tarmac rally stuff) where the road surface is constantly changing and the suspension is higher and has more articulation than a dedicated circuit car