I picked up some new tires for the rig and I'm going to mount and balance them myself. I'm going to use the stick on weights. My question is about orientation of the weights and why do people mount them as shown below? If there's enough flat real estate, why not mount the weights at 90 degrees to the orientation shown below? Mounting the way I'm thinking would place the weight in a more exact spot. Maybe I'm just wrong and not thinking of something because no one does it like that. What am I missing? Can someone explain it to me? Thanks.

 

On a skinny wheel (like a motorcycle or bicycle) you basically only have one direction of vibration, up and down. On tires of any appreciable width, like a car, you have secondary vibrations, like a wobble.

If you have an imbalance in the tire that is closer the inside or outside edge of the wheel, the weights must be placed accordingly to balance it out. Weights are strategically placed on the inside and outside edge of the rim. Placing weights the way you suggest would not be effective for this.

Imagine you had a 1 oz imbalance on the outside edge of the rim at 6 o'clock. If you put 1 oz of weight at 12 o'clock but on the inside of the rim, it will be balanced up and down (and always pass the spin test by stopping in a random spot), but it will be very imbalanced and vibrate due to wobble.