I am doing some mods to the 2006 Miata that I purchased from the estate of spin_out last year and I have a head scratcher that I would like some confirmation on before I accidently trash a set of new RE-71's.
In the past I have checked camber using a straight edge piece of steel the length of my rim diameter (18.25"), a level, and a precision measuring device. I place the bottom of the straight edge against the rim, and then use the level to make it perfectly perpendicular to the floor. At that point I measure the distance from the top part of the bar to the rim and use trig to calculate the angle. This method is used for negative camber.
My bar is 18.25" long and the gap at the top is .800" which by my calculations is about 2.5 degrees of negative camber. This is roughly what I plan to run and I am comfortable with this amount as a starting point.
I purchased a cheap camber gage with a magnetic base and when I place it on my steel straight edge and span the wheel touching it at both the top and bottom, it is reading 4 degrees of negative camber. I set zero using a level so I am confident in my zero point.
I tend to trust trigonometry and not the gauge but maybe I am doing something incorrectly.
I used this website for my trig calculations. https://www.calculator.net/triangle-calculator.html?vc=&vx=&vy=18.25&va=&vz=.800&vb=90&angleunits=d&x=50&y=25
Can anyone help confirm my trigonometry approach or correct my methods?
I can't but id love to follow along and see how this works out. Where do i find that gauge? (once we know if it works of course)
I honestly wouldn't trust that. Any discrepancy in the angle of the platform your vehicle sits on, you're gonna have a miscalculation. Not that you couldn't check the surface, itself, but I like the idea of good ole trig.
That all makes sense. Is the floor you're measuring on flat, not that it would change the reading . You DID do both measurements with the car in the same spot, right?
In reply to DeadSkunk (Warren) :
Yes, car was not moved between readings and they were taken back to back (no changes to the car at all).
Floor is level where I park it for checking alignment (I have the floor taped off to know where to park each time).
Did you get the same discrepancy on both front wheels?
Is there some sort of zeroing procedure for that camber gage?
Scott
I believe your trig is correct. I wonder about doing a few trials; set up spacers to set your straightedge on the ground at 0, 1, 2, however many you're curious about degrees, and see whether the gauge reads correctly if laid flat on the slope, and possibly using a square to see if it's a question of the measuring device being okay but the reference connection being janky (that stamped magnet holder foot thing doesn't have an aura of precision...)
In reply to noddaz :
Yes, the little thumbscrew that can barely be seen on the backside of the gauge in the photo is the zeroing device. It does zero just fine in reference to the (2) levels I have zeroed it out with.
In reply to Ransom (Forum Supporter) :
I set up a 24" carpenters square on a known flat piece of concrete (verified with a 2' level) and put the gauge on the 18" upright section. I then zeroed out the gauge as it should be very close to a 0 degree reference point. I then placed varying drill diameters under the far end of the 24" side of the level that was on the known flat surface and checked the gauge reading. It appears to be a gauge issue as it continued ot be off by a fair amount relative to the trig calculations.
In reply to Javelin (Forum Supporter) :
Same discrepancy on all 4 wheels and all were checked at least twice with both methods.
trucke
SuperDork
5/14/20 2:41 p.m.
I do something similar. I hang a plumb bob on a string over the fender and measure to the rim top and bottom same as you. Then I built a spreadsheet using the rim diameter for my trig calculations. I measure with a steel rule in millimeters.
Is there something you KNOW is a certain angle from vertical that you can test the gauge on?
I'm thinking a goniometer or something like that.
In reply to CyberEric :
No goniometer that I can access but it did prompt a thought to use my phone angle finder. Full disclaimer...I have very little confidence in the accuracy of my iPhone angle finder app but I figured it might align better to one of my two current measurement methods (trig or camber tool). The angle finder app aligned to within .1 degrees of my trig calculations and was 1.6 degrees away from the camber tool. So it aligned closer to the trig approach and not close to the camber tool reading. The trick with the angle finder app was to always make sure to move it further (more negative) first to -10 degrees or more and then slowly align it to the steel straight edge. This resulted in a pretty repeatable reading.
trucke said:
I do something similar. I hang a plumb bob on a string over the fender and measure to the rim top and bottom same as you. Then I built a spreadsheet using the rim diameter for my trig calculations. I measure with a steel rule in millimeters.
I concur.
And thank you to fusion66 - the reference and reminder to think about Mark made me smile.
I thought from the title that this might be about the conspiracy YouTube video I was sent this morning.
Will admit I don't know too much about measuring camber but when comparing your 2 measurements it appears like the gage is reading camber from bottom of the rim to top of rim and your trig may be calculating it from center (pivot point) to top of rim. Which would account for the reading to be double with the gage. Just my observation which may very well be wrong.
In reply to wlkelley3 :
In both cases my reference points are the bottom edge of the rim and top edge of the rim. Based on the confirmations above of my trig being good and the angle finder app confirming the amount of camber, I am going to move forward believing that I have 2.5 degrees of camber and not the 4 degrees the gauge shows.
Is there any run out in the wheel, play in the wheel bearings, ball joints or control arm bushings? That will cause inconsistent readings.
In reply to gearheadmb :
Everything is tight. I am not having an issue with inconsistent readings. The reading is the same at each wheel each time I check them, it's just that the two methods of checking yield different results and at this point I am 95% confident it is due to a poor quality camber gauge.
