Alignment or Suspension Related at 100MPH?

TreeSemdyZee

Tire pressure comes to mind also.

What are you running?

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Spooler

This has just been my experience with the 370z. It is the only real error that can happen on the stock suspension adjustments. As soon as I got the toe set correctly, no more issues. I drive just as fast on the interstate in the pouring down Georgia/Florida heavy rain as I do when it is dry. This is when it is most noticeable to me.

Need4Speeds

Alright, I'm scheduling another alignment check at a different shop that's caters to preping cars for autocross events and what not. I'll get a print out this time and post it up here to see what you guys think about the settings.

jchammond

Sounds good; be sure & have full tank fuel on.

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MaysEffect

Be sure they don't get crazy with the settings. In some cases a "autocross" setup implies you fudge up the standard alignment for faster steering and decreased roll in the rear. Do not let them go outside of .5 degrees (either direction) in the front and .3 degrees toe-in rear. You will kill your tires and most likely it will not benefit this car much.

As little camber in the rear, increase camber in the front.

Need4Speeds

Yes, I agree with you.

Rusty

You need a little more toe in. When your toe setting gets close to zero. The car will fell nervous. The faster you go, the worse it gets.

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Spooler

Dead in the middle of the spec is best. No fudging one way or the other with all settings. As stated above, Autocross and track setups are different. When they get it right you will know right away.

Need4Speeds

Wait, so do I want zero Toe in the front and back or just a tad bit of Toe In...in the front and Zero Toe in the Back? I'm all confused. Some of you are saying Zero Toe Front and Back and some are saying a little bit of Toe In

jchammond

2x more +toe in rear than front,,,look at chart & you may want to go between nominal & maximum,,,will give better straight line stability.

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jchammond

I originally had mine at .125"F & .250"Rear....kept a really straight line & gradually backed off till i got .094"F & .188"R-performing nicely.

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MaysEffect

In relation to the above info. Setting zero toe will allow the front tires to gain more toe out under compression in the front (braking/turning/bump). In addition to this, Adding toe-in on the rear (only) will actually increase the wandering on the front axle as it changes the pivoting angle slightly. As mentioned above, its best to set a bit of toe in on both axles. If you set zero toe front, you will actually get better high speed straight line stability with a bit of toe out in the rear. Under rear compression the car is set to toe in (acceleration/turn/bump). During cruising and hard braking however it may fish tail a bit more.

To mitigate both instances, it's best you get rid of the rubber lca bushings for something a bit stiffer.

Sorry for the oddly worded description. Typing from phone.

jchammond

Unsure about all the details that Mays says; but little or no toe in rear will make the tail end dance around-especially if you go negative.
Also; I'm pretty sure you supposed to line up the rear before going to the front..& this may sound weird & the alignment shop may not do it....but road test it good & then throw back on the rack..as it seems things will settle.
I performed my own alignment & had to tweak it over a couple week span-to get the drive & measurements I was looking for.
A real learning process.

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MaysEffect

I was just attempting to explain the dynamics behind what goes on during driving conditions. At most cases we'd be cruising at highway speeds. I concur it will slide around the rear with toe out when cruising. But under acceleration the rear is set to toe in. To be fair, it's not efficient to drive this way in daily conditions. But at the track, its advantageous.

If you are using the string and ruler alignment technique it doesn't matter which axle you do first as long as you are using some form of turn plate under all four wheels. If you're only using turn plates on one axle at a time, then yes, rears first, reset the string, then fronts. In all cases, doing it on uneven ground will result in a incorrect alignment no matter what. 1/2 inch of unevenness is enough to mess up accuracy. Plus J, you have massive tires so i can't imagine this being easy to do .

jchammond

May's;
It has been a learning experience for sure...no turn plates.
I tweaked a tad every day or 2 & kept up with all of my adjustments made;as the least incorrect adjustment & steering wheel can get mis-aligned.
Treadwear is very good on tires.

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