Prophecy99

iTrader: (1)

If you install small Front spacers (5mm max) would you need to do an alignment?

jeff5347

i dont believe so. your only spreading the wheels apart and spacers dont effect the toe in or toe out. I think you would be all set putting them on and be done.


By the way i have your phone on my cell as the wallpaper. Nice looking ride.

2slow

iTrader: (6)

An alignment is not necessary; as the previous poster mentioned, the spacer does not change the toe, camber or caster.

PulsarGTS

iTrader: (6)

Not needed, but I swear after installing mine the car drives sooo much better. All the steering wheel tug I would get when switching lains or on a wavy road is gone.

Prophecy99

iTrader: (1)

Just wanted to double check. Thanks...lots of pics to come this season with new camera and grille.

Thanks again.

Sounds nice, now off to the shopping, Do you have rears also?

Norm Peterson

Not directly, anyway.

There is a tiny indirect effect on camber and toe, but for only 5mm spacers the changes are nowhere near big enough to be concerned about. A change in the amount of steering kickback is entirely possible, and that itself may depend on what camber the wheels are at.


Norm

MorpheusZero

iTrader: (10)

Since the scrub radius will change the steering feedback will increase (how much depends on the current offset and scrub radius). Changes in camber and toe will be there since you're applying more transverse (perpendicular to the bearing axis) torque to the wheel bearing (increasing torque arm), but they will be negligible, even with a decent size spacer. I'd be very surprised if there was any noticeable change in alignment even with a 25mm+ spacer.

Norm Peterson

Mostly I was identifying that although the alignment changes are tiny, they do exist.

In addition to what the simplified kinematic diagrams show, kickback also depends on where the forces are applied to the tire. At significant negative (or positive) camber, the centroid of the disturbing force is not at the midpoint of the tire tread (where using just the diagrams implies it is).

A spacer also reduces the springs' overall motion ratio, so wheel rates and ride heights both show minor changes (lower for both) in addition to whatever happens due to bending in the knuckle and strut.


Norm

VQuick

iTrader: (17)

Norm, if you have time, could you explain in more detail how and why the wheel rate and ride height change with spacers? And what do you mean by "wheel rate"?

MorpheusZero

iTrader: (10)

You were showing off

From a practical standpoint there would be no difference.

If the front suspension were a swing arm, the wheel rate would be affected. Since it's a strut suspension and camber change through the stroke of travel is minimal, motion ratio really isn't changed.

And again, even if it were a swing arm, you would not notice a change in motion ratio (5mm spacer compared to a 24" swing arm? Even an inch spacer would be under 5% length change). Technically it would make a difference but really not anything that would matter, my bet is that most springs probably have a 5% tolerance in rate in the first place.

Norm Peterson

VQuick - wheel rate is the effective spring rate at the wheel. Spring rate and wheel rate differ because the spring does not act at the wheel location, or along the same line as the wheel travels, and generally at least one other very minor effect. In most strut suspensions, wheel rate is on the order of 90-95% of the spring rate.


Morpheus - don't forget that for purposes of rate comparisons any length ratio (or cosine, for that matter) gets squared, so a 4% length ratio drops the MR by about 8%. Earlier today I ran some really quick numbers for the swing axle of a Corvair-weight car (100 lb/in initial wheel rate assumed) and got a ride height difference of a little over 0.5" with 1" spacers, which corresponds to over 1.5° camber change. Seemed reasonable. A 5mm spacer working with a 120" front view virtual swing arm implies only an 0.33% wheel rate change (less than 1/32" ride height and 0.01° camber changes).

I'm an engineer and while I'm comfortable identifying small effects like adding 5mm spacers to a typical strut suspension as having negligible effect, I don't think it's proper to say or indicate that the effects themselves do not exist.

A 5% tolerance on spring rate drops out in a "before and after" comparison when spacers are added to an existing vehicle (though you certainly would consider it if you were working up an original design).


Norm

MorpheusZero

iTrader: (10)

Alright I'll give you that (lol at swing arm camber curve). However that belies the issue at hand--a vehicle with a more civilized camber curve such as the maxima's strut setup will not be affected nearly as much, seeing as the slope of the camber curve will have an exponential effect on alignment change (higher slope of camber curve dictates higher motion ratio change AND higher camber change per ride height change). In fact with our suspension at a certain ride height (where the camber curve is flat) there will be no motion ratio change at all.

Respect I'm an EE major a few quarters from graduation.

To the general public on a question like "will 5mm spacers affect my alignment?" I think it's ok to just say no. Between you and me debating is fine but it will go over 95% of the maxima driving population's head and be moot information anyway, for the issue at hand at least.

If you want to get technical then yes it does, but the point of the statement was to illustrate the relative change, i.e. we can't pick out one brand new set of Eibach springs vs. another on the same car even if the rates differ by 5%.

VQuick

iTrader: (17)

I'm not an engineer but I'm smart enough to understand the fundamentals of classical mechanics.

Morpheus, you guys are really in agreement here, so lay off Norm.

(Norm didn't say there would be a noticeable change.)

MorpheusZero

iTrader: (10)

We're having a technical discussion, contribute or shens

And for the record, I never said (or implied) that the effects don't exist, I just said they don't matter. Yeah if I lose a quarter then my net worth technically goes down, but no one cares because it's insignificant and not even worth mentioning, much like the alignment changes that a 5mm spacer will bring about on the front of a maxima.

Norm Peterson

Demonstrated. "A 5mm spacer working with a 120" (what? why 120"?) front view virtual swing arm implies only an 0.33% wheel rate change (less than 1/32" ride height and 0.01° camber changes)." BTW, that 120" comes from ~twice the track dimension and is consistent with the results obtained in a 2-D strut geometry spreadsheet using measured dimensions from a car of similar size.

Yes, camber gain is neither constant nor linear. But the slope of the camber curve is a consequence of the geometry, not the other way around. Where you are on the camber curve depends on suspension position, which comes from corner weight and wheel rate (which comes back to the complete definition of motion ratio and the spring rate).

Camber gain goes to zero when the control arm is perpendicular to the strut axis. Given the initial inclination of the strut and limitations on the amount of available bump travel, that may not happen. Or if it does, there may be a number of more urgent things on your mind.


Civil/structural here, with graduation a few decades behind me (Damn, I must be getting really old ).

I figure that there aren't any 'downsides' to putting more information into a reply rather than less. Readers can use as much of it as they choose, but at least there's a chance of sparking a little extra awareness. Or curiosity. It makes ME think a little more carefully and/or actually do a little research before I hit the 'Submit' button. And when I'm wrong or slightly off the track it makes it easier to find out where I needed to have thought some more.


Norm