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

Horatio Alger and/or one of his many clones is trolling again. Just check the source.

As to checking Camber "at home". When it comes to vehicular safety, when it comes to the lives of my wife, kids and grandkids, not to mention me, my advice is DO NOT TRY THIS AT HOME - as no matter how smart the phone, the operator will be an idiot.

Peter Wieck Melrose Park, PA

Ooooops.

I had forgotten to link to a descriptive photo of the desired task:

I'm sure there are gotchas (e.g., is the garage floor really flat?), but it seems doable to measure camber at home if we can answer the main obvious questions which are (I think):

Q: What accuracy is *needed* to measure camber at home? Q: What accuracy can be *attained* with a typical mobile device? Q: Is the repeatability sufficient in a typical home measurement setup? Q: How do we compensate for typical errors (e.g., ride height, flat floor)?

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

.01 degree or better.

?????????? don't use one myself

Same way you do with the machines, Measure the floor and level the machine prior to use. Using an app you could check the floor span where you plan to do the work and zero it out.

How to attach the device to the wheel/hub.

--
Steve W.

Not possible centered on the axle and neutral in two axis without additional (and expensive) tooling. Hence the "Idiot Operator" requirement.

Once again, Harmon/Alger is trolling for a Darwin Award.

Peter Wieck Melrose Park, PA

Not possible centered on the axle and neutral in two axis without additiona l (and expensive) tooling. Hence the "Idiot Operator" requirement.

Once again, Harmon/Alger is trolling for a Darwin Award.

NOTE: Azimuth accuracy in smart-phone devices (departure from the vertical) is typically less than 10 degrees. OK for orienting the picture on the pho ne, not so much for measuring tire camber. Pushing right up against the "Id iot Operator" requirement for trusting such a device for such a purpose.

It would be quite useful were the OP to actually make adjustments based on such a device - if we could only be sure when he inevitably wraps himself a round a tree thereafter that he does so without any collateral damage. Yes, I am being snarky - but if ever there was a situation for such - this is one.

Peter Wieck Melrose Park, PA

We really must know to what accuracy we need the measurements to be becuase every measurement tool ever made has this as its basic issue.

Do you think it's less, or more accurate that we need for camber measurement?

As just one reference, page 8 of this document says that camber (and toe) measurements must be accurate to "2 angular minutes".

The question then becomes how to translate 2 angular minutes into inch measurements.

On page 10 of that document it says the camber tolerance of another vehicle model is ? 10' (plus or minus 10 minutes).

So what is 10 minutes in inches?

I realize there are many ways to measure things, and I understand that you're using the tire wear and handling to measure camber, but I would like to try to get a bit finer in granularity (especially since lots of other things can cause both those issues).

I have plenty of carpenters bubble levels, one with digital output, so that's also another option.

I understand what you're saying which is that the negative camber on my rear tires can be anywhere between 0 and minus 2 degrees.

But I would like to get a bit more accurate than 1/4 bubble! :)

One of my cars specifies the following static camber range, for example: Front (non-adjustable) camber = -0.7? minimum, 0.3? maximum Rear (adjustable) camber = -2.2 ?mimimum, -2.0? maximum (

)

Some cars compensate for that by specificying cross camber specs, but mine are symmetric.

The static negative camber is "supposed" to increase lateral grip. At the same time, it certainly increases inner tire edge wear and decreases straight-line braking traction. On uneven road surfaces, you can get camber thrust (where the tire moves toward the camber).

Yup. That's a measurement and calibration issue for sure, but luckily, my garage is extremely flat (I measured it once long ago).

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?

This is a good hint, which is that we can just note what the *delta* is between the front and back, and measure that delta, over time, with a handy instrument.

Mine has negative camber on both front and rear, but front isn't adjustable without adding camber plates.

I disagree but I understand your point. On sheer economy, there are only 3 measurements I need for my sedan:

1. toe front
2. toe rear
3. camber rear

So all I need, to do a "pragmatic" alignment check, is to check those three. A. If they're off, then I can get the car aligned for $100 or more. B. If they're on target, then I save $100 each time I measure them.

On page 14 of the document above, it tells me that the static toe and camber accuracy needs to be: Toe measuring accuracy ?2' in measuring range ?2? in total range ?18? Camber measuring accuracy ?1' in measuring range ?3? in total range ?10?

Does anyone here know how to convert the 1 and 2 minutes to inches?

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

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?

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:

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).

I assume that is the wheel and not a hub cap. I'm guessing your looking for something between 0.5* and 2*, but I want to know. Someone said you need accuracy within .01 degrees, that's 1% of 1 degree. 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 don't have a clue about phone app accuracy, but you can check it. But hey, I've never done it, so don't read my response.

Mikek

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 later found this BMW spec which shows that I need accuracy in 1 or 2 minutes (

) but how do I convert that 1 and 2 minutes to inches?

I think he meant inches though.

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.

According to this graphic, I need to repeatably measure toe to plus or minus 2 minutes of accuracy and camber to plus or minus 1 minute of accuracy:

Static camber will be measured in degrees, so the plus or minus 1 minute of accuracy is easy enough for me to understand.

But sttic toe is usually measured in inches, so a problem is how do I convert the 2 minutes of accuracy to a plus or minus inch figure?

"John Harmon"

You can't. Minutes of angle are a function of a triangle. Inches are simply a scalar measurement of distance.

A jig, if you can't use the actual wheel.

No, But 30 min is equal to 0.5 degrees. Mikek

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.

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).

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?

Something wrong, 30 minutes is equal to 0.5 degrees.

1 minute is 0.0167 degrees, I don't think that's what you are after.

You might play with a trig calculator.

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.

Mikek

That depends on the length. Mikek

>

You are well-and-truly an idiot!

The measuring device must be accurate to one one-hundredth of a degree, or two decimal places. The measurement itself will be far less sensitive than that, probably to a single degree, no more. But if I am staring (for instan ce) at 90 degrees and want to get to 89.75 degrees - hence the need for tha t level of accuracy.

Azimuth on the typical smart-phone (how accurate is it a measuring off the vertical) is typically somewhere between 8 (at best) and 15 degrees - and t hat only if it has a screen-orientation function. Many do not. And many mor e have only a 90-degree function and only in one direction.

Put another way, the phone is smart enough not to even attempt the process. The idiot owner who insists that it is possible - with the right app/softw are - deserves exactly what he gets.

Minutes are a circular unit-of-measure. Not a linear unit. So, "inches" wil l be measured at some point on a diameter as compared to another point alon g that diameter using a fixed radius. If 'vertical' minutes, one endpoint o f that radius will be the center of the earth. If other than vertical, the determining endpoint will be something hopefully more nearby such as the ax le or some specified point. And the diameter on which the distance is measu red will be specified.

But, minutes do not convert to inches other than the chord defined by the s tarting point and the end point of the measured distance along the total ar c.

False premises lead to false conclusions. I am calling you an idiot as you seem congenitally unable to understand the most basic geometry - previously most basic physics - yet insist on some sort of false precision to draw ot hers into your idiocy as an actual problem. It isn't. Otherwise, you are a simple (very simple) troll. Yeah, I am responding - in the same way that ou r grandkids enjoy Wack-A-Mole at the penny arcade. You will probably never go away, but well-turned invective can be enjoyable, even if against a help less target.

Peter Wieck Melrose Park, PA

Sort of mixed units.

For a circle with radius about 286.5 feet your circumference will be about 21,600 inches so each minute of arc will be one inch. I don't think that helps you here.

--
Andrew Muzi 
   
  Open every day since 1 April, 1971

The accuracy of the level application on my one phone is out bt over

7 degrees. That is a simple "level" app.. The "rigid" level application on my Blackberry PlayBook is very accurate - How you reference it to the wheel will be the biggest variable that can through your accuracy off. A trammel type setup made from a straight bar of metal (or "straight" hardwood) with 2 screws protruding to reach the edge of the rim, adjusted to be identical in protrusion, will transfer the wheel angle accurately to the "level". You can determine if the rim is true to the spindle by checking the level with the bar upright with the wheel turned 180 degrees to make sure the reading is the same with the wheel turned.

WITH CARE you can check your camber to a reasonably high level of accuracy. To get the camber "normalized" you need to roll the car back and forth a few feet so the car "settles" on it's suspension. A professional setup uses a "slip plate" that allows the wheels to slide in and out with little resistance. Normal procedure is to bounce the car on the slip plates to "normalize" the suspension.

I've done it long pre-smart-phone using a simple bubble level to verify the alignment was "close enough" afterr an accident in central Africa severely damaged the front of my Peugeot. I've also done hundreds of alignments with "pro" equipment.