Not familiar with the wheel, but Like BobA said, most newer wheels don't use pots for the steering wheel.
(and therefore aren't as easy to hack)
Here's what the one on my Logitech Momo wheel looks like.
(bottom gear on the back of the feedback motor is the encoder wheel)

It also has another sensor and a silver strip on the steering column so it knows where center is.
I'm still working out the kinks of hacking it. I'll probably have a test-bench setup this weekend.