Does the Z have a rear toe-steer problem?

Guard Dad

What you are describing is toe-in when the rear suspension is in a compressed condition and a toe-out in a rebound condition, am I correct?

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2010 Brilliant Silver, Base w/Sport Package, AT7, Katzkin leather, upgraded audio and lots of Dynamat and a bunch of small stuff.

Guard Dad

In your case did you change the torque arm length or did you set it at the stock length? The implication of the Megan product description is that by adjusting the torque arm length the toe characteristics can be altered-your experience suggests otherwise. Comments?

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2010 Brilliant Silver, Base w/Sport Package, AT7, Katzkin leather, upgraded audio and lots of Dynamat and a bunch of small stuff.

ChrisSlicks

It is more track oriented than street (mine is from SPL). First they eliminate the rubber bushing to get rid of random flex, and second you can use it to alter the bump steer slightly. But like I said before I'm not sure that the suspension is compressing enough to actually induce bump steer in your case, but rather the back end is bouncing off the bumps as a result of the spring rate, or to be more accurate wheel rate as Red pointed out.

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kenchan

ha!

softening the rear damp rate will not help, actually will make it worse.
swaybars will not help in this case either.

it's completely related to the amount of stroke, toe-in angle on the rear, and damp rate. ive already experimented with this on my G35C and it's got a similar suspension geometry. it's a programmed design of this kind of suspension. i already mentioned on my earlier post on how to reduce this feel. this is another reason why im not running lowering springs on stock dampers.

Guard Dad

So your thinking shocks are the first option?

Somewhat off topic (maybe) but I notice that those forum members that install coil overs always seem to comment that the ride has improved. This seems counter intuitive considering that most of these applications involve a 1.5" to 2" drop which, in my experience, usually makes the ride choppy and harsh. Now back on topic. Are our shocks known to be a problem? Is improved ride with coil overs the result of better shocks (I'm not interested in a sloppy ride) or is something else going on here and can any of this in any way be used address my concerns about bump steer?

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2010 Brilliant Silver, Base w/Sport Package, AT7, Katzkin leather, upgraded audio and lots of Dynamat and a bunch of small stuff.

Red__Zed

the shortened torque arm and adjusted angle on the 370z changes things a bit vs the g35. The change results in the car generating additional toe-in under corner load, and if you take dynamic toe measurements, you will generally notice that the 370z is prone to over-toe, whereas the g35/350 struggle with stability due to no toe gain. It is a big part of the reason the 350 was unpredictable on corner exit.

kenchan

if that was true, dont you think i would've jumped on c/o's 2 yrs ago?

the reason why my car has stock springs and dampers is to maintain balance and stoke for street. the car can use stiffer dampers so this is why ive been thinking about running koni's and using stock springs. lower ride does not = better handling. actually it worsens it on street as it's not a controlled surface like on the track.

kenchan

the principle is the same. the rear toes-out as the suspension compresses. that's why the wiggling butt. the 370Z is much improved vs the G35C, but as i mentioned, the design shares the same principle.

Guard Dad

Is more toe going to eat the rear tires, or do you just bias it to the factory maximum spec for toe in? Whose dampers do you like?

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2010 Brilliant Silver, Base w/Sport Package, AT7, Katzkin leather, upgraded audio and lots of Dynamat and a bunch of small stuff.

kenchan

more toe-in condition (0.40 total) will eat at your tires, but it will improve straight line stability for sure. but stiffer dampers will net your a lot more on this type of suspension.

on stock springs i think im going to be okay with koni yellows which are only re-bound adjustable (yellows are usually only re-bound adjustable and i am assuming the same for the 370Z's set). unfortunately this is the only damper set currently available for the 370Z that i know of. my only other alternative would be to get coilovers with near stock spring rate, linear rate springs, and keep stock ride height, use the adjustable damp settings to tighten up a little bit.

if im running progressive rate lowering springs i would prefer to have simultaneous adjustment dampers for street (bound and rebound stiffens together like my tokico D-Specs on the G...but not available for the 370Z). my goal would be to minimize suspension movement since it's already sitting near the outer stroke range of the stock suspension from the lowering springs... sacrifice would be some ride comfort. tires are eating pretty quick but i was able to get ~10K with sprited driving on RE050A PolePositions so that's not bad at all (currently running the new S04 PolePositions ).

Guard Dad

Kenchan, Red_Zed, I'm learning a lot here but if I'm reading your posts correctly kenchan says it toes out under compression and Red_Zed says it toes in under compression. Pick one.

My butt-o-meter suggests that the rear suspension gains significant toe in as it compresses because the car smartly (more like abruptly) steps back in line as the suspension compresses as it lands on the far side off the bump. If the toe change is radical enough that it goes to a near zero toe or (worse) a toe out condition at full droop when it launches off the bump and then gains a lot of toe in on compression we might be onto something as such a behavior would cause the condition I seem to be concerned about.

Comments?

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2010 Brilliant Silver, Base w/Sport Package, AT7, Katzkin leather, upgraded audio and lots of Dynamat and a bunch of small stuff.

Red__Zed

except the shortened torque arm creates toe-in on compression. the funky wandering feeling described here (and in many other threads) comes from excessive toe-in.


I can't speak for the G35 for sure, but when I did bump steer measurements on my 370, I started at ~1/16*, and went to ~3/32* at full compression on the rear.


You can hook your Z up to a bump steer gauge if you don't believe me.

Guard Dad

Regardless of toe in or toe out, firmer shocks would reduce suspension travel and minimize undesirable toe changes,

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2010 Brilliant Silver, Base w/Sport Package, AT7, Katzkin leather, upgraded audio and lots of Dynamat and a bunch of small stuff.

Guard Dad

Would an adjustable torque arm allow you to tune out some of that toe change?

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2010 Brilliant Silver, Base w/Sport Package, AT7, Katzkin leather, upgraded audio and lots of Dynamat and a bunch of small stuff.

Guard Dad

Red_Zed, am I reading that right a total increase of 1/16" additional toe in? Is that from full droop to full compression?

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2010 Brilliant Silver, Base w/Sport Package, AT7, Katzkin leather, upgraded audio and lots of Dynamat and a bunch of small stuff.