I have the t rims on my GN and the clear has long since been gone.
The best to get the wheels real clean is Eagle - Mag and wheel cleaner for roug cast alum.
It is a strong acid so it will get the funk off.
Spray on (cool wheels) let it sit for a min or 2.
Spray some more on start scrubbing with a stiff nylon bristle brush(wheel brush).
Spray soime more on and then blast em off with highest psi water you have.
This will get them very clean but will dull the smooth areas.
Now you get the never dull, mothers, paste/liquid alum polishes, etc and start working on the flat areas arond the outside and the tops of the spokes and walla time will pay off. This is the prices to pay since the clear is gone on our wheels. I thought of powdercoating mine clear in the future but it would have to be a high temp powder coat cause the front wheels get pretty freakin' hot.
Good luck