Originally Posted by
Scottrik
To do it properly would require a jig and a mill to make sure you don't affect caster and/or camber as you remove material. This is NOT a job most racers have the appropriate equipment for.
Note that IRS may have discontinued the modified AE arms they were doing, but have done so because they have released their own arm they themselves designed and are molding. Instead of the marginal gain seen by modifying the AE arms (they only "lower" it 1/16") the new IRS lower arms go WAY lower. You can run the front tires right down to the rims if that's what you want to do.
These new arms are EXCELLENT pieces, but I STRONGLY recommend purchasing a 8-32 RH tap (about $5-6) and properly cutting threads into these rather than mashing screws through them to make threads. The design is very good but creates a stress riser where the upper arm mount is let into the lower arm. I've seen these arms crack along these risers when threaded with a screw...I've never seen one crack that has been properly tapped.
Scottrik
The other great thing about these arms is that they are universal left and right. I found at least for me if I attach the caster block before threading the screw in then I don't have problems with the screw hole cracking.
I have noticed one issue with them that is irritating me though. They are not level left to right. The right side arm seems to be near .5mm lower then the left side. I'm not yet sure if it is the arm itself or the pivot ball placement in the arm. At first I thought it was the body moldings being off...but then I changed cars and the problem still existed. Once I figured out it was the arms I checked the 4 other cars running the IRS arms here and found they all had the same problem.