Advice requested from those of you who have successfully checked camber at home

On Thu, 8 Dec 2016 20:12:14 -0000 (UTC), John Harmon
> wrote:

>Steve W. actually said:
>
>>> Q: What accuracy is *needed* to measure camber at home?
>> .01 degree or better.
>
>Thanks for that answer because this is a critical number we must know to do
>any aligment reasonably well.
>
>If everyone concurs that 0.01 (one hundredth) of a degree is the desired
>accuracy, I can work with that.
>
>One problem with alignment is that we have to be intelligent about
>converting units because I found this document where, on page 11, it says:
>

> Quick-acting clamp + measuring sensor + computer = 1' at a
> measuring range of ? 3?
>(all BMW vehicles are within that ? 3? measuring range).
>

>http://www.bimmerboard.com/members/s...tem%5B1%5D.pdf


>
>But I don't (yet) know how to convert 1 minute to inches.
>Does anyone want to take a stab at how to run that conversion?
Pythagorus' theorem -, or better yet, trigonometry. Or a triangle
calculator like http://www.cleavebooks.co.uk/scol/calrtri.htm Solve a
triangle. You know (from your measurements) the base of the triangle
(distance from spindle) and the height (difference between the
projected line and "straight"), or the base and 2 angles (the desired
angle and 90 degrees) to calculate the height. One way tells you what
angle you have, the other gives you the distance measurement you WANT.

>
>>> What other gotchas will we need to look at to successfully measure wheel
>>> camber using a mobile device in a typical garage setup?

Your biggest problem is getting your head around all the concepts.
>>
>> How to attach the device to the wheel/hub.
>
>It seems to me that a "jig" of some sort needs to be made so that there is
>a plane on the wheel that is (very precicely) parallel to the wheel to the
>same 0.01 inches that we need for accuracy.
>
>My initial idea is to take this concept to that 0.01 degree:
>http://i.cubeupload.com/6CPUl7.jpg
>

On some vehicles it CAN be that simple -- On others it is definitely
a wee bit more complex, but you have the idea.
>Maybe bolt a flat steel plate to the wheel lugs (luckily, one of my cars
>uses lug bolts so I can just use longer bolts but my other car uses lug
>nuts which may make that flat plate bolting on more difficult).

And the length of the studs/bolts gets critical - not to mention it
works best with 4 or 6 studs - not so good on odd numbers like the
common 5, or the less common 3 stud wheels.

On Thu, 8 Dec 2016 20:17:43 -0000 (UTC), John Harmon
> wrote:

>amdx actually said:
>
>> I assume that is the wheel and not a hub cap.
>
>The car I will test this out first on is a bimmer with alloy wheels and lug
>bolts so both those traits make the task of bolting on a jig easier than if
>it were a steel wheel with lug nuts.
>
>> I'm guessing your looking for something between 0.5* and 2*, but I want
>> to know.
>
>I later found this BMW spec which shows that I need accuracy in 1 or 2
>minutes ( http://i.cubeupload.com/cfaDWp.jpg ) but how do I convert that 1
>and 2 minutes to inches?
>
>> Someone said you need accuracy within .01 degrees, that's 1% of 1
>> degree.
>
>I think he meant inches though.
>
>> Good luck getting the 18 year old at the tire shop to do that.
>> I'd be happy with 10%, being that it is an adjustable characteristic
>> that can depend on how you want to drive the car, comfort or cornering.
>
>I understand that the alignment shop guy might not care all that much to
>get as accurate as he can.
>
>Right now, I think the accuracy needs to be plus or minus one minute for
>toe and 2 minutes for camber.
>
>I just don't know how to convert minutes to inches.
There is a saying about Bimmers.
If you have to ask how much - for anything - you can't afford to drive
a bimmer.. There are enough things that can go wrong in the front end
of one of those kraut-wagons that I think you are definitely being
penny wise and pound foolish trying to save $100 on the maintenance of
a late model Bimmer. Don't be such a cheap-ass. - or drive a Chevy.

You want to know if anything is worn or bent - and measuring CASTER is
required as well to know. You really don't have your head around the
concepts well enough to understand WHY an alignment check should be
done properly. Your "quick check" is just that - and if you are at all
in tune with your car as a driver you will know there is something
wrong just as well by simply driving the car. If you are not "in tune
with the car" the Bimmer is wasted on you --- (as it is on the vast
majority of Bimmer owners)

On Thu, 8 Dec 2016 21:13:31 -0000 (UTC), John Harmon
> wrote:

>Phil Kangas actually said:
>
>>> I just don't know how to convert minutes to inches.
>>
>> You can't. Minutes of angle are a function of a
>> triangle.
>> Inches are simply a scalar measurement of distance.
>
>That's bad news because both the toe and camber are specified in degrees
>but when I measure toe, it will be in inches.
>
>At least when I measure the camber it will be in degrees so I won't be
>switching units back and forth.
>
>I know how to physically measure toe in inches (e.g., with a string); but I
>don't (yet) know how to measure toe in degrees with a smart phone or
>digital level.
If you are going to measure the toe with a string, you may as well
forget about it. You can NOT get enough accuracy or repeatability to
determine if the toe is correct or not. Without pro equipment, to get
that granular in your measurement you NEED to extend your measurements
5 or 10 feet and measure with a goor steel tape measure, or extend the
displaced centerline accurately and measure with a steel rule. Using
the simple tape measure will give you the total toe - which will be
double the specified toe per wheel, and will not tell you if you are
off-center.

On Thu, 8 Dec 2016 21:13:33 -0000 (UTC), John Harmon
> wrote:

>amdx actually said:
>
>>> That's excellent advice. Since the tire bulges, I wonder if it's best
>>> to use the wheel lugs to mount a jig which is what we measure to?
>> A jig, if you can't use the actual wheel.
>
>I agree that, for our purposes, we should assume I jury rig a jig of some
>sort so that there is a flat completely perpendicular plate bolted onto the
>axle somehow (probably placed on the outside of the wheels using the lug
>bolts or lug nuts).
>
>>> Does anyone here know how to convert the 1 and 2 minutes to inches?
>>>
>> No, But 30 min is equal to 0.5 degrees.
>
>Right. And the 1 and 2 minutes are 1/60th and 1/30th of a degree
>respectively.
>
>But what is 1/60th of a degree in inches?
That depends whether it is at 12.5 inches, 12.5 feet, or 12.5
miles.......
You REALLY need to study your high-school math.

amdx actually said:

>> But what is 1/60th of a degree in inches?
> That depends on the length.

Following that statement to the logical next step, here is a
representiative track for my sedan from this thread:
http://www.bimmerforums.com/forum/sh...nsion-Overhaul

That photo says that the track is:
- Front Track Width = 1512 mm
- Rear Track Width = 1526 mm

So now what's 1/60th of a degree, in millimeters?

On 12/8/2016 6:54 PM, John Harmon wrote:
> amdx actually said:
>
>>> But what is 1/60th of a degree in inches?
>> That depends on the length.
>
> Following that statement to the logical next step, here is a
> representiative track for my sedan from this thread:
> http://www.bimmerforums.com/forum/sh...nsion-Overhaul
>
> That photo says that the track is:
> - Front Track Width = 1512 mm
> - Rear Track Width = 1526 mm
>
> So now what's 1/60th of a degree, in millimeters?
>


You have a misunderstanding, to figure millimeter or inches,
you need to have two lines that are connected like a below,

l****/
l /
l /
l /
l/
The angle between l and /, we will call 1/60 of a degree,
the **** is the millimeters or inches, BUT, the quantity of millimeters
or inches depends on the length of l, as you can see the longer l the
larger **** will be. But the angle stays the same.


Use the link below
may help you see it.



http://www.carbidedepot.com/formulas-trigright.asp
I put in a 1 degree angle for (angle a) and 16" for
(side B) Then hit calculate to find (side a).
This says you need 0.279" of tilt top to bottom
on a 16" wheel.
Note: this triangle is rotated 90* to your wheel.
So take that into account when thinking about the calculation.
Bottom line, for a 1 degree angle you need a tilt of 0.279" over 16".
That's measurable, but you need a post 90* off the floor to measure from.
Second note: Side (a) the tilt at the top (mm or inches), Side (b) is
perpendicular to the floor, Side (c) would be the tilt of the wheel.
Angle (a) is the degrees of the angle you set.

Mikek

On Thu, 8 Dec 2016 20:12:12 -0000 (UTC), John Harmon wrote:

> translate 2 angular minutes into inch
> measurements.

Sheesh, you don't translate angular measurements into linear ones.
An angle isn't a length. Cheers, -- tlvp
--
Avant de repondre, jeter la poubelle, SVP.

On Thu, 8 Dec 2016 20:37:59 -0000 (UTC), John Harmon wrote:

> so a problem is how do I
> convert the 2 minutes of accuracy to a plus or minus inch figure?

You need a cataly$t, and a good front end man. Bring your vehicle to the
front end man, lubricate him with your cataly$t ($100 should do nicely),
and he'll perform the conversion for you, even adjusting things to the
result you would desire (key word or phrase: "wheel alignment").

HTH. Cheers, -- tlvp
--
Avant de repondre, jeter la poubelle, SVP.

On Friday, December 9, 2016 at 6:00:52 AM UTC+8, Bill Vanek wrote:
>
> 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.
>
Depends on type of suspension. Live axle will not change.
Control blade has miniscule toe change under power.

tlvp actually said:

> Sheesh, you don't translate angular measurements into linear ones.
> An angle isn't a length. Cheers, -- tlvp

I agree that I'm confused (which is why I am hesitating to respond because
I don't wish to muddy the technical issue further for everyone).

The problem with doing camber at home is different from the problem of
doing toe at home.

For my bimmer, the camber is specified in degrees, and the measurement
tools we're exploring measure in degrees.

We just have to solve the conceptually simple problem of
a. Accuracy to 1 minute of angular measurement
b. Creating a wheel plate that meets that accuracy
c. Measuring to that accuracy with a mobile device

The problem, for my bimmer, is that the manufacturer specifies the toe in
degrees, yet we measure in inches. The conversion confuses me to no end
(which is obvious to all).

However, that specific translation problem may be solved if I trust this
layman's chart, for a similar vehicle:
http://www.bmwdiy.info/alignment/index.html

Which puts the toe-in in inch measurements of:
Front toe (left): Minimum = 1/32", Maximum = 3/32"
Front toe (right): Minimum = 1/32", Maximum = 3/32"
Front toe (total): Minimum = 1/32", Maximum = 3/16"

As with all specs written by laypeople, I can't tell if that toe is to the
centerline of the bimmer or wheel to wheel but since they specify a
single-wheel toe, can I safely presume that the spec is to the *centerline*
of the vehicle?