Did my alignment, and now the car does this...

[Icehouse]

Yeah if there is one thing I learned from all the 3D modeling the of front suspension  it's that "looking" at suspension can tell you basically nothing.  Until you've moved ONE point 1/4" do you realize visually suspension is magic.   I've always found this factory bump chart interesting.  If bump steer sucks why do they design it into the suspension?

 

 http://the510realm.com/download/file.php?id=34850

[datzenmike]

heywier, you mentioned you have 280z "steering knuckles", Is it possible the arm is longer, or shorter than the 510? And if so would that contribute to steer diving? 

 

A longer arm would slow the steering input... more steering turns needed to turn the car, but less effort and would favor high speed steering being less sensitive. A shorter arm would quicken the steering but more effort needed and would favor cornering and be more responsive.

 

The steering arm would be tilted down at the back more as the castor is increased. Probably not a factor but

[heywier427]

Hi Guys,

 

Again, thanks for all the responses.

 

280z steering arms are shorter, so less steering input needed.

 

It finally stopped raining and I re-did the alignment with "better" results.

 

This new to me bear alignment machine needs you to do a swing after every castor measurement (doesn't adjust on the fly like my 25 yr old machine!).

 

So, I can now see my castor measurement, and am a bit perplexed.

 

It says Im +1.86, and my Vintage Historic's adj, t/c rods are 100% maxed in on adjustment, but my wheel looks very far forward. I will ask them if thats all they go, but I doubt it.

 

Camber -1.8

 

Toe +.24

 

The car is now more difficult at parking maneuvering, but is in no way unmanageable, leading me to believe I need more. I adjusted my camber plates to more of a caster setting (tilted back towards the rear of the car), but did not max them out, as i would loose camber some adjustment.

 

Car is better. Drove over 100 miles yesterday, almost all back roads! Still a bit twitchy, but not that unpredictable feeling I was getting before.

 

Tonight I am going to detach my rear sway bar, and see what difference it makes. I will also try the front (both detached at the same time), but with the softer springs Im running, I would imagine I need them both (200lbs front / 175 rear).

 

I was able to determine the vibration is the cv joints do to the lowered suspension. I thought i would be fine, as Im not slammed, but no...

 

I ordered the poly rear sub-frame bushings, as well as poly diff mounts. Was not planning on doing any of that until I found another rear subframe to modify with the camber brackets and spherical links. Finding stuff on the east coast is tough. Ive got a line on one in the next few months though. Hopefully.

 

Got it up to 120 in 3rd! Progress! Surprised the sh!t out of an SRT Neon :)

[heywier427]

 

 

 

Bumping up the springs is the next step.

 

I have a 12a rotory up front, so fully dressed with trans is +/- 350 lbs.

 

How does that compare to other engines?

 

I guess I will corner balance and weigh it tonight as well.

 

Maybe 250 up front 225 in rear?

 

Ill let you know how it weighs out.

 

Thanks,

 

Tom.

[Cardinal Grammeter]

My 2¢:

 

No one mentioned tire temps.

 

I set my toe-in exclusively by tire temps on all my cars.

 

And when I've done that (including setting pressure), each adjustment results in more and more grip.

 

And I get even tire wear.  And if one side camber is off, one tire will wear the inside while the other tire wears the outside.

 

After trying all kinds of wire, plumbs, lights, etc. I will never set Toe other than by temps.  (If I would get to the point that I need turn-in or some road race characteristic, then toe becomes a subjective setting.  But I think the starting point is from balanced temps.  Also, temps depend on the nature of the driving or course, but for street it seems not to be an issue and I do tear up back roads.)

 

Also back in 1970 (!) a friend of mine put a 289 in a Falcon and had to replace the bottom ball joints.  They came as a lower control arm assembly.  He didn't check, put them in, and if you let go of the wheel, the steering to go to lock depending on which side of center you were on. 

 

The control arms he installed were the wrong length.

[datzenmike]

Tire toe is tire toe regardless of temp(erature)? Are you trying to say that in the winter the toe is different than the summer? Not following....

[Cardinal Grammeter]

If you are trying for even tire wear, the temps have to be spot on.

 

But in a performance, race alignment, you compromise wear for handling characteristics - but keep in mind, every form of road racing does their final temperature calibration at the track.  I don't know what their criteria is but I'm guessing they also are critically aware of tire wear minimization.  Even F1 runs crazy negative camber which is just spooky to me and then don't even talk about dirt trackers.

 

And this is really the biggest advantage of temps:  Its the only way to set your tire pressure and actually know you have done it precisely.  When you see a tire with burned out centers, you lower the pressure, but its really too late, the center rubber has been squandered.  And far worse is that you have no idea how much air to let out of the tire to get to the balance point.  And you might want to run underinflated to spare the centers and use up the sides - tire temp can do that for you - in fact, you can start by running the opposite profile you just measured!

 

What "blew my pants off" (Fallon) was the astounding amount of grip I picked up when I did this.  In my case it was toe and pressure that were adjusted in 3 iterations, each one yielding a very noticeable increase in grip.

 

And finally, I highly mistrust electronic "black boxes" that perform alignments.  Those machines are subject to calibration and don't even think about if the mechanic drops an alignment head - like he is going to tell his boss he did that.

_______________________

 

Example of how different temps for different driving styles and roads:

 

Suppose you drive like ordinary person around windy road and set your temps.

 

Then you drive like crazy ape over same roads.  Here you start rolling the tires over and burn out the edges.  Temps will show this.  And so like every AutoXer knows, you increase your tire pressures.

 

Once you've worked out the temps for a set of tires and conditions, you can set your pressure for a long interstate trip, around home, or track day.

 

(and I'm pretty sure I read this one on a Datsun road race thread - maybe here?):  for AutoX you put shoe polish on your sidewalls and further increase pressure until you only scrub off the tread portion.  If you have to increase your pressure from the previous tuning, that means you need more neg camber and probably caster.

 

 

You can also think of it this way:  a colder region on the tire means that area was not gripping as much.  And so, on average, you probably want all the areas of the tire doing their fair share.

 

Of course, the slower the turn, the more critical speed is because that dominates lap time.  So you probably want to bias grip for the slowest turns which is now problematic since you are no longer interested in average temp over time.  How this is handled beats me, but I'll bet it is very technical. 

 

That's all I know, maybe 5¢ worth   :frantics: :frantics:

[heywier427]

This thread is going to go dormant unfortunately due to northeast weather :(

 

I redid the alignment, and found a mistake I made. I did not divide the tow # in half, and was running too much. That combined with poor caster will probably prove to be the issues.

 

The Vintage Historics adj. T/C rods are meant to be used with off center camber plates, hence the reason I could only get 1.xx caster. I let them know how awesome it would be if they would mention that in there description. Would probably have avoided this thread.

 

I have since turned the plates to allow for more caster, and removed material off the face of the T/C mount (vintage historics suggestion, and my thought as well) to get myself to a maximum of 4.86 caster on both sides. Should be plenty.

 

If the weather gets nicer I will take her for a spin.

 

Cardinal, using ir temps for toe/tire wear is a great/simple idea. Will see what the temps do.

 

Hurry up summer time!