Exactly how important are rear traction rods?

[Tearlessj]

I'm finally piecing my suspension together. I just want to know how important is it to get the rear traction arms? I've heard that I can adjust the factory arms? If it doesn't make too much of a difference I'll go ahead and get a alignment without them.

[projectRDM]

You cannot adjust the OE arms. OE settings change camber and toe only, and are very limited. The only way to adjust while staying OE is to slot the arms at either end, giving you an oval hole to be able to move the arm a bit, but it's a janky way of doing it.

However, the main reason to adjust the traction arms is to dial out bumpsteer, depending on how your car is set up you may not need to adjust them at all.

[s14unimog]

I would say absolutely necessary. How can you expect to extend your RUCA and not extend your traction arm? Without them, you'll have a hard time getting your rear end straight.

[!Zar!]

No huge reason to buy them. Though I've heard most guys are cutting/welding the stock one like 10mm or something sorter? I forget the exact amount.

[NeedCAforS13]

I would say absolutely necessary. How can you expect to extend your RUCA and not extend your traction arm? Without them, you'll have a hard time getting your rear end straight.

I think you're talking about the toe arm... but maybe I'm wrong?

[s14unimog]

That one is necessary too. I may be wrong but after slamming my s14, and we're talking just bottoming out a set of flexes, so nothing crazy, it looked pretty necessary to me, just to get the rear end in alignment. Just think about the geometry, seems obvious enough to me, but maybe I'm wrong. All three of mine are adjustable. I think the lower is the only one that's not necessary; unless you want to get into a lengthy discussion about roll centers, which I'm not that educated on.

[NeedCAforS13]

"traction links are not for toe adjustment. they're to correct bump steer - toe change through suspension travel.
toe is adjusted/set with the rear toe links."

I only did RUCAs and toe rods myself.

[s14unimog]

^ I understand this. but if you crank out on your RUCA, which is connected to the top of the spindle right next to the traction arms connection point, then you'll redoubtably twist your spindle...

[NeedCAforS13]

To me the correct answer is: if you're going all out on your suspension and you want it to handle as best as it can with proper geometry - get all 3 arms.

If you just want to lower it and get it to proper stationary alignment specs you can get away with just the RUCA's and toe rods. My current car, and previous S13/14's that I've owned with just RUCA's and toe rods all drove straight and didn't eat tires.

[projectRDM]

^ I understand this. but if you crank out on your RUCA, which is connected to the top of the spindle right next to the traction arms connection point, then you'll redoubtably twist your spindle...

There's enough play in the bushings to work with, and the locating points allow for the camber arm to move a good bit without binding anything. You have to realize that lowering the car changes the geometry anyway so the 'twist' you suggest doesn't apply. It doesn't hurt to have a pair but usually adjusting them any substantial amount greatly effects the car's handling.

[jspaeth]

There's enough play in the bushings to work with, and the locating points allow for the camber arm to move a good bit without binding anything. You have to realize that lowering the car changes the geometry anyway so the 'twist' you suggest doesn't apply. It doesn't hurt to have a pair but usually adjusting them any substantial amount greatly effects the car's handling.


Can you elaborate on this....how the traction rods effect the handling? If there is a way to adjust them and have a POSITIVE effect, I wanna know!

I have all adjustable arms in the back, except for the lower control arms, which are stock.

I have lowered the car around 2" maybe in the back, and then brought the camber back to around -1.5 and the toe is pretty much near 0.

Never had to touch the traction rods tho.....is there something you are suggesting I can do that will have positive benefits?

[aznpoopy]

Can you elaborate on this....how the traction rods effect the handling? If there is a way to adjust them and have a POSITIVE effect, I wanna know!

I have all adjustable arms in the back, except for the lower control arms, which are stock.

I have lowered the car around 2" maybe in the back, and then brought the camber back to around -1.5 and the toe is pretty much near 0.

Never had to touch the traction rods tho.....is there something you are suggesting I can do that will have positive benefits?

yes. for lowered cars, you lengthen the rear traction rod. benefits are as described above, but actually figuring out how much to lengthen it is not something many backyard mechanics / typical alignment shops would know how to do. for that reason, most people leave it at stock length or lengthen it (as what they describe as) "a little."

[PoorMans180SX]

The traction rod affects caster in the rear which effects the rear camber curve.

Depending on the static camber you're running in the rear, you usually want to lengthen them on a really lowered car, this makes your camber curve "smoother" lessening bumpsteer and helping traction.

[jspaeth]

The traction rod affects caster in the rear which effects the rear camber curve.

Depending on the static camber you're running in the rear, you usually want to lengthen them on a really lowered car, this makes your camber curve "smoother" lessening bumpsteer and helping traction.

Okay....camber curve being how camber changes versus bump in the rear (aka how much camber you gain as the suspension travels upward?).

And because of the geometry, as you travel upward, this changes both the camber AND toe?

So lengthening the traction rod casues the toe/camber change upon suspension travel to be smaller?

is that correct?

[SoSideways]

Okay....camber curve being how camber changes versus bump in the rear (aka how much camber you gain as the suspension travels upward?).

And because of the geometry, as you travel upward, this changes both the camber AND toe?

So lengthening the traction rod casues the toe/camber change upon suspension travel to be smaller?

is that correct?

In short, yes.

The best way to learn about the effects of the traction arm, is for you to literally go out to the car, take out the rear coilovers, disconnect the sway bar, and play with the traction rods.

Obviously mark the rods to where the original settings are before you mess with them, duh.

Before you adjust them though, go ahead and move your wheel/suspension up and down the entire range so you can get a feel for what it does in the current setting.

Then, on one side, lengthen it like 10mm like a lot of folks do on slammed or lowered cars. On the other side, shorten it 10mm, just to give you the extremes on either side of the adjustments to exaggerate the effects.

[S14DB]

Question is, can the average shop adjust them?

I can have the Caster, Toe and Camber done on the front. But, the machine only does Camber and Toe in the rear where I goto.

[jspaeth]

Question is, can the average shop adjust them?

I can have the Caster, Toe and Camber done on the front. But, the machine only does Camber and Toe in the rear where I goto.


I don't believe there is any way for a typical shop to "detect" the adjustments.

As I'm sure you know, caster in the front is only measured indirectly by having the technician/aligner person guy turn the wheel, and it measures change in camber with respect to change in toe as the wheels are turned.

So yeah, you are right....because clearly the shop can't turn the rear wheels.

I am guessing with a very stiff suspension setup and little rear suspension travel, the effect is probably not a very big one, but I just asked out of curiousity.

[s14unimog]

You have to realize that lowering the car changes the geometry anyway so the 'twist' you suggest doesn't apply. It doesn't hurt to have a pair but usually adjusting them any substantial amount greatly effects the car's handling.

okay but this is different than just moving the suspension through its full range of movement. You will have literately increased the length of a solitary suspension arm. How could that not affect the closest arm to that point?

[EDacIouSX]

how exactly do you adjust the traction rod for bump steer. Everyone says BUMP STEER ADJUSTMENT, but how do you adjust it for bump steer?

[projectRDM]

okay but this is different than just moving the suspension through its full range of movement. You will have literately increased the length of a solitary suspension arm. How could that not affect the closest arm to that point?

Look at the arm locations and their pivot points. It's not like a square box where pushing one corner outwards moves the other corner inward. The two upper arms are right next to each other at the upright but are farther apart on the subframe end. The shock also is not centered with the upright, it sits behind the axle, at the rear edge. With both arms unbolted you can move the upright fore/aft and in/out easily, it's not like one side binds the other from moving. The amount of regular camber adjustment does not effect the traction rod at all as when the camber arms pushes the upright outward, the toe arm is used to pull it back in to keep both angles correct. The traction rod just locates the two on a fixed pivot.

With extreme camber/toe correction you would run into an issue as the pivot point is maxed out, but rarely does that happen on a daily driven car, even significantly lowered. The main reason for using an adjustable traction rod is to eliminate the rubber bushing on the subframe end. A competent race shop like Gran Turismo East is the only place I'd feel comfortable adjusting the rod and making sure the bumpsteer isn't worsened.

[jspaeth]

how exactly do you adjust the traction rod for bump steer. Everyone says BUMP STEER ADJUSTMENT, but how do you adjust it for bump steer?


If you look at where the traction rod sits, it's kind of like lengthening it or shortening it wants to move the wheel along the axis of the length of the car.

So, bc of the way everything is connected, lengthening it or shortening it changes the way that toe and camber change as the suspension travels up and down.

You have to listen to these people that actually know what they're saying....there are quite a few of them that have posted in this thread

[!Zar!]

It isn't really called caster for rear adjustment. It is called thrust.

With caster/thrust adjustment you are moving both the front/rear wheels for/aft and thus changing how your car tracks.

They touch on it here.
http://www.scoobymods.com/howto_4_wheel_alignment-t7388.html?

[projectRDM]

how exactly do you adjust the traction rod for bump steer. Everyone says BUMP STEER ADJUSTMENT, but how do you adjust it for bump steer?

The absolute best way is to know exactly how your car feels when driving in a controlled environment, say a track, at it's limits. Bumpsteer is varied in it's effects based on wheel angle, load, etc. and is harder to dial out in the rear. In the front, you simply lengthen the tie rod shank to compensate for the control arm's increased angle, but since the fronts wheels turn the bumpsteer is more apparent, and thus easier to diagnose.

Honestly even tracking my old car at both autocross and road courses over several years I never touched the traction rod length.

[nieko]

If you slam your car, you will need to lengthen the traction rod to keep it "stock-like."

Stock your rear wheel is pretty much in the center of the wheel well.

After you slam your car, its really far forward.

like a gti when its slammed lol, but they have a solid rear beam, theyre just fucked. lOL

[wh0aitznic0]

Good thing I searched and found this thread...

So in short, I'll ask this question:

Will my (albeit CAPABLE) alignment guy know what to do with the Traction arm for Caster/Thrust when I take it in to him? Because S14DB said alignment shops don't measure rear caster.

[eklips3]

could you get away with only RUCA's in the rear for a few degrees of camber without running toe rods ?

[fliprayzin240sx]

could you get away with only RUCA's in the rear for a few degrees of camber without running toe rods ?

Will depend on how low you are. Stock Toe rods barely has any adjustment on it. Usually you get both RUCA and Toe rods to be sure. Then if you're slammed, sometimes the Stock Traction rod will start pulling onto the Toe rod and thats when you need traction rod to correct your alignment.

[ManoNegra]

NRR has a pretty good thread going on this subject:

New S14 bumpsteer graphs - Nissan Road Racing Forums (http://nissanroadracing.com/showthread.php?t=1652)

[nieko]

good thread.

very good thread.

[rocksteady_racer]

Caster adjustment - if your going to a shop with the electronic alignment machine, I know because I complained at R&S Strauss up here in phila to get my caster right in the front of my 240sx. Anyway, what the alignment technician needs to do is keep it on the first screen and not go in to the alignment menu. The screen with all the gauges before you go into the alignment adjustment section. The machine will then be able to read caster. It just doesn't read caster inside the alignment menu because all cars have fixed caster in the front and they don't want their technicians playing with it - they'd rather if it's out to replace the whole arm. So just tell him not to go into the alignment menu to adjust the caster then do the rest of the alignment in the alignment menu ;). Hope this helps everyone who is having a similiar idiot shop technician who doesn't know how to work the alignment machine for non-stock cars ;).

[!Zar!]

Er this thread is talking about thrust settings.

In the rear.

Not caster up front.