Camber measurement conundrum

[oldcodger]

Hi,

Long story short  - measured the camber using one of the typical camber bubble gauges, similar to the gunsons one, and used a spirit level with two bolts so it sits on the rim properly as, there is no suitable flat surface on the alloy wheel.

The gauge give a reading of  eg   - 1.65 deg , though its a difficult thing to  get an accurate reading.

Seeing some details on the web, many use bolts in the spirit level that can be adjusted, so adjusted the top bolt until the spirit level shows even and then read off the difference, in this case 5.7mm.   Following the formulas given on several sites the 5.7mm over a 412mm rim gives   - 0.8 deg  .

Have done several measurements and all seem to be very similar in the different between the two method.

Can anyone explain what I have done wrong ?

Have to assume the bubble gauge is right and thats what to use to adjust the camber /strut to the correct value ... though it seems far easier and more accurate to read it by the spirit level method and a vernier gauge?

Typical diy camber gauge, page down  a bit  http://www.the289register.com/members/Technical/Issue 11.htm

 

[oldcodger]

Well problem solved,  as the picture above shows the gauge I ordered  is specified as,  and  calibrated  to   - +6 degree.

Now proven by manual means  that its actually -+3 degrees.

Seems a Gunsons one and some other eBay China makes are -+3deg, as show below,  so can only assume they have assembled / mislabelled the one I got. 

Bit of a job when we buy a test instrument but then have to prove if its accurate !