What causes this:

http://img10.imageshack.us/img10/482...1102900059.jpg

I've tried using the mothers chrome products but it doesn't seem to have helped at all.

 

Cheap chroming usually pits or starts to deteriorate well before a good chrome job, which is hard to find anymore and when you do it is exp.. Once it starts there is no way to stop it..

 

Cheap chinese chrome. 90% of the wheels out there are chinese junk.

 

my chrome 22's have some light pitting, and i polish mine every week.

when it gets real bad, im going to get them PC...

 

Guess my torque thrust are cheap two of my rims are starting show their age(front ones). Back ones look new still. I've tried 4 diff brands including mothers they all shine but won't help when this starts happening

 

Salt will cause chrome to pit. Some people up north will take their chrome wheels off during the winter months because of all of the salt spread on the roads to melt the ice. I don't know if you ever drive your truck close to the ocean but a strong wind could pick up tiny droplets of water containing salt and carry them to land. But I would say the chrome job is the main culprit because of the amount of pitting you have.