Now that I've done some more research, I have a better handle on 'toe' so
I'm going to agree with you that getting toe precise to 2 minutes isn't all
that important, in all likelihood.
For *setting* toe, especially in the rear, it could easily be that 0 toe
(degrees or inches) would be just fine, or, maybe, to take up some
suspension slop, a "smidgeon" of toe (maybe 1/16th of an inch or less in
linear dimension no matter what the wheel/tire diameter).
This is to take up the slop in the suspension (perhaps slightly more in the
front if it's a typical RWD like all my vehicles are).
I'm still confused how to convert toe from degrees to inches, but luckily,
there are web sites that will do it for us.
Interesting you mention that, because the reason for the *far away* wall is
simply that the angle is small, right?
If you are talking about toe, I'm no expert, but the way I understand it is
that you lock the steering wheel in the center position first (which has
nothing, per se, to do with alignment but with esthetics) - and then - you
pick a side, and twist a tie-rod ever so slightly - which - depending on
the direction of twist, moves the front of the wheel in toward the
centerline of the vehicle - or outward.
So it's one wheel at a time, measured to the centerline.
Of course, you can assume all sorts of symmetries and do both wheels at the
same time, but conceptually I think of toe as a wheel-to-centerline thing,
to be done one at a time.
That's an interesting observation that the measurement problem is more
difficult, but I think only if we try to measure degrees of toe.
If we measure inches of toe, the measurement problem is conceptually
I'm trying to find the triangle in the equation of toe in order to figure
out how to convert the distance measurement to an angle.
Here I just drew what is my first pass guess at where that triangle lies:
Is *this* the trigonometric angle everyone is talking about?
You make a good point here in that we really have a 3-dimensional X, Y, and
Z axis, each of which is rotated by 90 degrees (caster, camber, and toe).
Just to ask to get me more firmly grounded, is *this* the triangle everyone
is talking about?
email@example.com posted for all of us...
+5 and high school math... He could go back to school and learn all this for
less bux than he wasted-not to mention our time.
Drive it to the BMW shop and tell them you want it set to the preferred
settings. Make certain all your bushings and arms and their esoterically
named crap is brand new because as it wears it will change. Don't hit any
curbs, potholes, driveways, obstructions of any sort, or drive it period.
Better get new springs too as they will sag and take everything out of the
trunk. If it's a convertible weld some stiffeners along the top. Have your
partner and you control their weight. Fill up with gas first. Get all
pebbles, stones and other safarcus out of the treads. Make certain the tire
pressure is within a 10/th of a pound. I am sure I am forgetting
If you can answer this question then it will show that you actually
understand what you call *simple math*.
Here is the question:
Summarized, that says: If total toe is the difference in toe between the
rear and front of the tire, and if the difference in angles between the
rear and the front of the tire are exactly the same (by definition, since
the angle of the wheel/tire combination to the centerline of the car is the
same no matter what size the wheel/tire combination is!), then how the heck
can total toe be specified in degrees?
On Sat, 10 Dec 2016 22:37:01 -0000 (UTC), John Harmon
I replied to your original question days ago, and you ignored that
reply. Regardless of that, your questions have been answered
repeatedly. Toe *is* an angle, but if you know the outside diameter of
the tire, it can also be spec'd in inches, or any other linear
measure. The conversion involves only the measure of sides of a
triangle, which is really basic math. This is my original reply:
Inches depends on the outside diameter of the tire:
Minutes to degrees can be found here:
Regarding the needed accuracy, it depends on exactly what you are
trying to achieve. There is a wide range in camber that will not cause
any meaningful tire wear. Toe is much more critical, including for
overall feel at higher speeds, but you are also dealing with runout,
and there really isn't any good way to adjust for that at home.
The overall point is that even if you are off with the camber, the
tires are not going to be worn out all that much earlier, so close can
be good enough, especially if you bother with rotation. Toe is much
more important, and if you want that exactly right, pay someone to do
it right. You can get it close at home, but it's just luck if it's
You also have to keep in mind that a rear drive car's toe out will
increase with speed, and a front drive car will do the opposite. There
is plenty of slop in steering & suspension, and you will get varied
readings, especially if you are not using turntables. Sometimes trying
to save money is not such a good idea.
At the same time, finding someone to do the job right can be a
challenge, too. There's plenty of hacks out there.
If all you care about is getting things close enough that there won't
be ridiculously excessive tire wear, then have at it. But if you are
trying to get things just right, both for handling and tire wear
purposes, pay someone.
I had/have no problem with the trigonometry, since it's simple soh cah toa
stuff, these triangles.
My main problem is where was the triangle.
It seems to me that, if toe is specified in inches, then the triangle
should be specified at some known point off from the center of the wheel to
the centerline of the car.
If they specify toe at any other point than a known point off from the
center of the wheel, then they have to specify how far they are from that
known point for any inches-to-degrees conversion to apply.
Isn't that right?
I completely understand that measuring inches from the tire tread to the
centerline of the car and then using that as the "opposite" in the
trigonometric soh cah toa, will come up with the wrong angle which will be
more and more wrong the further the measurement is taken from the center
point of the wheel.
When they specify toe in inches, why don't they just specify it from the
rim of the wheel (instead of from the tread of the tires?)
I can convert with basic sohcahtoa trig but I need to visualize the
I have learned a lot about this accuracy problem since I opened this
thread, which I can summarize as no basic home tool will get the accuracy
specified by BMW (which is 1 minute for camber).
However, you really don't *need* that accuracy (which is what you are
An inclinometer will get us to about 1/10th of a degree (six minutes) of
accuracy as stated on thisadvertising blurb:
A typical smartphone apparently uses either a gyro or a magnetic compass
and accelerometer, which can't get to the same accuracy (it seems) as an
inclinometer can (or so I'm told).
However, in the end, a "smidge" of negative camber (about a degree or so)
is probably in the accuracy range we really need, which a smartphone can
Static toe is actually easier to measure and harder to measure than camber,
It's easier because it's easy to measure distances and then convert those
distances to degrees using basic sohcahtoa trig.
It's harder because you can't easily measure degrees of toe with a typical
inclinometer level or smartphone gyro/compass/accelerometer because they're
based on gravity which is in a different plane for measuring camber angles
as it is for measuring toe angles.
BMW does not recommend ever rotating tires, but they don't care about tire
wear. The camber is only adjustable in the rear and it's pretty high (I
forget but it's at least 2 degrees negative camber for each rear wheel).
That wears out the inner edge like you can't believe.
Me? I'm ok with zero camber but that can't be obtained (the last alignment
proved that). But I think 1.5 or 1 degrees was what the guy was able to get
So, for me, the camber setting would be to simply put it at the lowest it
will go (least negative) for the bimmer but for the toyota I have a wider
range (where only the front camber can be set because the toyota has a
solid rear axle so nothing is settable).
As for wear, it seem everything goes in this direction:
In that caster is done first, then camber, and then toe, and in that wear
is least with caster and then more with camber and then even more with toe
(under typical settings).
It's just x y z planar stuff. :)
I have done my toe when I replaced tierod ends, pitman arms, and idler
arms, and then when I took the cars for alignment, the toe was spot on.
So I think toe is easy, compared to caster and camber.
I'm an old man who has never had a FWD car and I hope that I die before I
ever stoop that low.
So all my questions are for RWD vehicles.
The simple test is to set the alignment at home, and then take it to the
shop for double checking. Many shops offer free tests if nothing needs to
be changed; but I would hesitate to take them up on that only because they
can always find something so I suspect that's just a gimmick.
Has anyone here ever gotten the "free test" actually for free if there was
nothing to change? Or do they always find "something"?
Never in my life (and I'm an old man) have I seen a mechanic install a tire
correctly (I use Tire Rack authorized installers), so I suspect it's the
same with alignment.
For example, I had to bring 500 pounds of my own weights to my last
alignment. The alignment guy *knew* how to do it right, he just knew that
most of this customers don't have a clue.
It's the same with the tire mounting shops. They *know* how to do it right,
but they also know most of their customers don't have a clue so they get
I doubt a single car tire is installed correctly, by the book, on any car
taken to the typical tire shops (wheel works, goodyear, midas, etc.).
I think the summary is this simple.
A. Check the alignment at home for the things that can be adjusted.
For my Toyota, that's only caster, camber, and toe in the front, and for my
bimmer, that's only camber and toe on the rear and toe on the front.
B. Adjust if necessary (using a smart phone or inclinometer for camber, and
a tape measure for toe). I'm not sure how to do caster in the toyota since
I only just found out that the caster is adjustable on the toyota.
C. Take it to one of those "free if it's ok" shops, and see what they get
If I'm perfect, it's free (I assume); if it needs adjusting, then I learn
what can and can't be done.
On Sun, 11 Dec 2016 01:07:00 -0000 (UTC), John Harmon
The old standard was always about +- 1 degree, when you had no other
specs to go by. Enthusiast cars like the BMW have different needs for
That's not uncommon.
That doesn't sound right. 2 degrees should not cause early wear, so
you really need to check the ride height. And recheck the camber.
Yes, caster will not cause wear.
That's not the reason for the order, but it's not important.
I hate to say this, but you can get pretty close just eyeballing toe
and camber. Especially with camber, if you can't see any substantial
lean, the camber is probably close enough that it won't cause tire
wear. In a pinch, it works for toe, too.
It's not necessarily a repeatable test, though. The one time you do
that, you might have gotten lucky.
They are expected to print out the readings, so it takes some effort
to lie. I'm sure they usually find something, but that's only because
cars do go out of alignment.
I'm pretty sure that none of the manufacturers expect techs to load a
car before alignment anymore. The specs take into account average
And I doubt that it makes the least bit of difference.
You don't really learn that, except for each time you try it. You can
get very different results on future attempts.
I just looked that up for my two cars.
The Toyota spec for the front camber is -.6? to .9? which is exactly in the
range you suggested.
The BMW rear camber E39 I6 and 540 models with "standard," "low slung
sport" and "M-sport" suspensions spec is apparently -2 deg 10 minutes. The
tolerance varies among options: either +/- 20 minutes or +/- 25 minutes of
The M5 spec is -1 deg 50 minutes perhaps due to 275/35 section width tires
vs 225/55 for I6 cars.
For the caster on the toyota of 1.7 to 3.2 degrees, I am not yet sure how
to measure it for the Toyota but I won't have to bother for the bimmer
because caster isn't adjustable.
For the camber of -.6 to .9 degrees for the Toyota, I think I'll use a
magnetic base inclinometer such as the Husky 10-inch Home Depot electronic
I think I'll just set the toe to 1/16th of an inch less in the front tread
(measured as close to centerline of the wheel as possible) than in the back
tread to centerline of the vehicle.
That will give me a total toe of 1/8th inch on the Toyota.
I'll use toe plates and a tape measure, I think.
True. But it would be free if I got lucky! :)
But if I align it first, it should be within spec, at least for what can be
aligned, which is, for the toyota, front caster, camber, and toe, and for
the bimmer, rear caster and toe and front toe.
The 500 pound loading on a bimmer is for a different purpose.
You are supposed to put 100 pounds on the driver seat, 100 pounds on the
passenger front seat, and 200 pounds evenly spaced on the rear bench and
100 pounds in the trunk.
That artificially "lowers" the car to a specific "ride height" which all
BMW alignment specs are to.
There is much discussion of why BMW uses that artificial ride height to
normalize all their specs, but it has absolutely nothing to do with the
"typical" loading of a vehicle with a driver.
I mostly agree with you that when the tire shop torques *all* lug nuts and
bolts to the same 100 foot pounds, it probably doesn't hurt anything. Nor
if they fill up all tires to the same 40 psi, again, it won't kill anyone
(even though BMW specifies different pressure for the front versus the
That they pry off the BBS hubcaps with a screwdriver just breaks the
plastic tabs. And that they don't remove all the old weights just makes
them put more on each time (and increases the chances of an imbalance from
a lost weight).
And that they don't mount the tire with the red or yellow dots to the valve
stem or match mounting mark just means they'll use more weight than
That they don't even torque the bolts in a star pattern probably only makes
the wheel slightly crooked.
So, I agree with you that the fact that no tire is ever mounted correctly
isn't causing accidents left and right.
But it's still wrong.
The problem I have is confusion about where the triangles are for toe, and
it has absolutely nothing to do with high school math since the trig
involved is easy (soh, cah, toa) if we only knew where the triangles are.
For example, total toe is specified in *degrees* of all things.
Yet, total toe is simply the toe measured at the back of the wheel/tire
combination minus the toe measured at the front of the wheel/tire
combination, both of which are *linear* measurements.
Since toe angles are the same no matter what size the wheel/tire
combination, how can total toe be specified in degrees when it's measured
Since the tire has the same angle the entire time, there is absolutely no
difference in angle between a toe measured at the front of a wheel/tire and
a toe measured at the back of that wheel/tire!
So, sure, I'm confused because total toe is specified in degrees.
But the confusion has nothing to do with high school trig.
Summarized, if total toe is the difference between toe at the rear of the
tire and toe at the front of the tire, yet, the angle of the wheel/tire
combination to the centerline of the vehicle is the *same* no matter how
large a wheel/tire combination is, then how the heck can total toe be
specified in degrees?
But angles are the units that the manufacturer provides for toe while I'm
almost certainly going to measure toe with a distance measurement.
The manufacturer specifies the "total toe" as 0 degrees 14 minutes plus or
minus 10 minutes:
The manufacturer specifies a "total toe" required accuracy of plus or minus
2 minutes in a measuring range of plus or minus two degrees with a total
measuring range of plus or minus 18 degrees.
So this confusion is all my fault.
Clearly I'm confused because the way I think of toe is linear, but the
manufacturer specifies toe in angles, so I should not have brought up toe
in the first place.
Camber is simpler because the manufacturer specifies angles and the
measurement is in angles.
So we should stick with camber for this thread (because it's a simpler
This article states that you can get as accurate at home as you need to:
Here's how they measured toe-in, for example:
Notice they measured toe in linear measurements.
That is a nice total-toe-in-inches to degrees calculator, which takes into
account wheel size, but I'm still a bit confused how total toe can *ever*
be an angle, when the angle at the front of the wheel is exactly the same
as the angle at the rear of the wheel?
It's not the math (the math is easy); it's the concept of total toe having
anything whatsoever to do with degrees when it's merely the difference in
toe between the front and rear of the tire when the angle at the front and
the rear is (by virtue of straight lines) exactly the same!
In this case of converting toe angle to inches, it's much easier to
visualize why single-wheel toe is specified in degrees.
Here's a diagram I made which shows that concept, which I agree is very
simple trig (soh cah toa):
Thanks. It seems that the order is "caster, camber, and then toe", in so
much as the two vehicles I have (toyota, bmw) both specify that you adjust
in that order.
Caster affects camber which affects toe so that's why you do it in that
Intererstingly, from the standpoing of tire wear in normal settings, the
same curve applies which is that caster affects tire wear less than does
camber which affects tire wear less than does toe.
So the order to think of the 3D axis are caster, camber, and toe (in that
order) for the x, y, and z axis.
On Sat, 10 Dec 2016 22:49:28 -0000 (UTC), John Harmon
That is not at all what total toe means. 0 degrees of toe for a wheel
is when the tire is exactly parallel to the centerline of the car
(that is a simplification, but it's usable here). Toe is a measure of
the variance in degrees from straight ahead. Total toe is merely they
sum of the toe in degrees of both the left and right sides. So if the
left is +2 degrees, and the right is -2 degrees, the total toe is 0
degrees. That means minimum tire wear (theoretically), but the
steering wheel will be a bit off-center.
The difference between the front and back of the tires is used only
for distance measure, not angles.
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