would you take these to a machine shop or take a grinder to them

[AussieK5]

Ditto...the difference in weight between various valve stems (rubber vs steel vs long neck stems) at the outer portion of the rim will have far more effect than a few grams +/- at the centre. I'd mark out a centered circle and die grind to it.
For that matter is there weight added/subtracted at the opposite edge on the rim to compensate for the valve orifice and fitting when its cast or rolled. Not that I've ever seen.

 

[pvfjr]

Double ditto for the last two posters. It's all right here.

 

[DEMON44]

bada bing X3 .....I took the die grinder to mine. works just fine. they're lug centric, and removing some mass from inside the bolt circle, literally 2.35" from true center. its not going to be a problem.


tips.....USE an aluminum specific carbide bit, and use lots of lube. it helps prevent the alum from galling up the bit. I had some of this wax based solid cutting lube at work. worked great, really speeds up cutting time and decreases bit cleaning time. I was doing a rim in about 10 minutes. opening the hole up to 4.75"



you CAN make a jig for a hole saw useing the bolt holes some studs, nuts, and flatbar..........but I couldn't have been bothered.