romandian

2008 c6zo6.

i move the wheel 22.5° left and 22.5° right (1 turn each) and get a total camber change of 5.8°. according to the ballpark-formula i get: 57* x 5.8/45 = 7.3° for castor. does anybody have notes of camber changes (1/4 turn, 1/2 or 1 turn each or lock to lokc) and the corresponding (verified) castor to check the calculation? (i realize the simplified formula works best for small angles, but my gage has a repeatability of about 0.2°, so i prefer doing a full turn.)

*57=180°/pi

Sub8

From one of David Farmers incredibly useful guide:

Measuring Castor
These measurements are based on the C5/C6 steering ratio of 16:1. While you can get
“relative” castor of any vehicle, the “multiplication factor” for absolute Castor is only for
cars with 16:1 steering ratio.
1. Start car, as you’ll need power steering.
2. Turn wheel exactly ½ turn to the right
3. measure camber of each wheel, marking left and right (be sure to make note of
positive and negative camber)
4. Turn wheel 1 full turn back to the left, or ½ turn left of center
5. measure camber of each wheel, again making not of positive/negative.
6. Subtract total camber change on each side
7. Multiply the camber change by 2.62 for total castor on that side.
Example: When turned to the right, your left wheel might read –2.0 camber. When you
do the full turn left, the same wheel might read +2.0 camber. The camber change would
be 4.0 degrees (+2.0 – (-2.0)). SO, the total castor on the left wheel would be 4 x 2.62, or
10.48.
The advantages to more castor are (1) self centering of steering wheel (2) increased
steering feel (3) more dynamic camber in the turns. While absolute castor is of some
importance, getting the castor nearly equal side-to-side is important to reduce steering
“pull”
***these measurements are based on a sin approximation, and should be quite accurate.
However, I’m relying on the steering ratio to be correct AND the user to make repeatable
measurements. If you are aligning your street car and about to buy an expensive set of
tires, you might want to consider visiting an alignment shop***

davidfarmer

I’ve used my method which is based on the published steering ratio, and I’ve used commercially available caster gauges with turn plates. There is always some variation.

honestly now, if I’m just getting a vehicle symmetric I simply get both sides within about 1/10deg camber change (without multiplying)…..but if I want raw numbers I measure them directly from the spindle

romandian

how to measure from spindle?

for 1/2+1/2 turn camber change is 3°. toe change is 21,4°. my calculation: 3/21.4x57=7.99. david: 3x2.62=7.86. 360°/21.4°=16.8. however 720°/45=16. so it all pretty much agrees.

for posterity: camber gain for outside wheel at this setting is 0.7° at 1/4 turn.

davidfarmer

De
Depends on the model, but the brake caliper holes on my car are writhing 1/10deg of the balljoints

mfain

On my Speedtech uprights with C6 ZR!/SKF hubs my caliper bolts are not conveniently aligned, but for initial set up I use the top two hub mounting bolts - they are dead perpendicular to the ball joint line. Also makes it easy to measure caster gain with compression. However, they are hard to use for caster measurements with the hubs installed.