Checking camber: it surely can't be as easy as it seems?

[Slipper man]

I was pretty sure my camber settings are wrong, because the negative camber looks far too much to the naked eye. I don't have a camber gauge, so I thought I would try my o level trigonometry. The diameter of the wheel rim is about 355 mm. If that is my hypotenuse, being the line connecting the top and bottom of the rim, I want the angle between the verticle (taken from a spirit level) and the hypotenuse. The horizontal distance from the verticle to the top rim is 30 mm. My sine finction on the calculator gives 3 deg from this.

 

In other words, at these very small angles, 1mm horizontal distance measured from the vertical with the spirit level placed against the lower edge of the wheel rim is 1/10 of a degree of camber. So all I need to do is set the distance at 15 mm and I have the correct 1.5 deg.

 

Have I got that right? It seems too easy to be true!

[philwaters]

I think when I did something similar I used the Inv Tan function - as you can measure the Adjacent (the 355 rim diameter) and the Opposite (the difference according to the vertical spirit level).

I used some Ali angle and put long bolts through at 355 centers and then locked one with a Nyloc each side and the other with normal nuts, so it could be adjusted. I could then measure each bolt length, subtract one from the other and obtain the Opposite length. I was also handy to check that both side were the same.

 

So, Opp / Adj = Inv Tan, or 12mm / 355mm = Inv Tan or 1.9°.

 

Phil Waters

[philwaters]

Thinking about it - I set the distance of my bolts at 355mm so that they picked up when vertical, while you are using the actual wheel. In which case, yes, Inv Sin = Opp / Hyp:

12mm / 355mm Inv = 1.93° - bloomin' close to the Inv Tan figure actually, certainly close enough that measuring inaccuracies make it pointless worrying

 

However, I can't get your 3° figure with your 30mm... 30 / 355 = 0.084, Inv Sin = 4.84°

 

I used 12mm in my calcs as that is roughly what I have mine set, close to 2°.

 

DISCLAIMER: It's been a long time since I did anything the long way - I use CAD these days

 

Phil Waters

[philwaters]

Cad Drawing.....

 

Anything to save me going out in the cold and getting my air filter to clean!!!

 

Phil Waters

 

Edited by - philwaters on 24 Dec 2007 15:54:28

[6speedmanual]

Yes! It's that easy!

 

Of course, stating the obvious, it is worth:

 

Checking the car is on a level floor

Loaded to correct operating weight

Tyre pressures

etc...

 

Camber angles anything between -1deg and -2.5deg quite acceptable depending on how you want your handling.

 

Athough camber easiest to measure, the other geometry angles are just as important.

 

A full set-up for corner weights and geometry is a good investment.

 

 

6SpeedManual

*tongue*There's no such thing as too much BHP per Ton 😬

 

Edited by - 6speedmanual on 24 Dec 2007 15:56:38

[CharlesElliott]

Yes, it is that easy but you need to measure it whilst sitting in the car on a totally level surface - this is what makes it more difficult!

 

Charles

---

My SuperGraduates 2006 diary

My SuperGraduates 2005 diary, My Caterham Academy 2004 build and race diary

[Mark Durrant]

I agree with Charles as most garage floors are not level

 

Mark D

Comp Sec

 

[Slipper man]

My garage floor is pretty good. I had forgotten about the weight though. My car was pretty well set up - I had it flat floored from new, and the corner weights were re-checked a couple of years ago and were OK. My problem is that when changing the set up for radials I forgot how many turns of the knuckle was one degree. I think I did twice as many as I should have done...