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The degrees a wheel turns and the degrees your steering wheel turns accordingly. You have to measure the actual degrees of one and then the other. Wheel alignment turntable is helpful. Without a turntable, I have heard of people using trash bags under the tires and measuring the degrees.
I don't know what it is for your car, but I do normally do it with a straight edge, toe plate, and a sharpie on the ground. It will get you the numbers you want. I do the calibration to the steering wheel (helps the driver) and then the steering wheel to the outside (of the corner) wheel for under/over steer calculations.
I've had a few people say it's not always linear and really suggest doing it on a turntable, but I've not taken the time to do that yet.
I would think it is essentially exactly the same - within machining tolerances
Ray
It's not that simple. Due to the Ackerman steering geometry, in a turn your outside wheel will be on a different turning radius than your inside wheel.
I haven't seen inside wheel angle used in any formulas, so I'm not sure ackerman geometry is anything to worry about. All the formulas to quantify understear that I've seen use the outside steered wheel angle.
The easiest way to see understeer is an x-y for steering to lateral G. That will show it quickly as steering angle increases and lat g doesn't. You can also compare those two in a regular strip chart to compare them and also look at the shape of the lat g graph near the peak.
If you have tire temps, you can often see it there as well.
Finally, you can use a few different steered wheel formulas to compare against the actual steering angle to find the delta as either over or under steer. These are especially helpful if you want to quantify the amount of understeer so you can compare setup changes, tire degradation, and other factors.
This allows you to calculate the THEORETICAL steering angle.
In order to determine the ACTUAL steering angle, I have used data from a slow speed outlap and scaled my steering sensor data to superimpose on top of the theoretical steering angle from the formula above. (In my case, I divided my steering sensor data by 22 and got a good fit). For the oversteer/understeer calculation I simply subtracted the difference in the absolute values between the theoretical and actual steering angles. The visualization pretty much confirmed my butt feel.
Visualization for Watkings Glen (my car was pushing like crazy) Red is Understeer - Blue is Oversteer:
Visualization from NJMP Thunderbolt:
Detailed Visualization for the Octopus which also confirmed my butt feel:
08-03-2017, 10:00 AM
slightly different for each car, but someone might get you close.
