I just had a set of Conti-all season tires mounted on our IS350. The tire guy (America's Tire) noticed that both the front wheels had a ton of lead on them to balance the tires from the factory. No exageration, like 6-8 onces per wheel. The rears were no bad, 1-2 onces. Well they dismount the stock Dunlops and get all the Conti's mounted then head to the balance machine. The throw a front on and spin it up. I was watching the wheel for runout and saw no visable runout at all. Sure enough the first one takes 4 onces to balance. That is crazy. That should be well beyond a manufacturer's specification. They break the wheel tire back down and rotate it on the rim 180 degrees. Rebalance and get the exact same results. Toyota/Lexus seems to have some extremely poor cast wheels to be that far out. I had no plans to invest in aftermarket wheels but I may have just changed my mind. Side note these wheels weigh a ton. I didn't have a scale handy but the rears feel like 30+ lbs. Curious to see if anyone else can see how much balance weight is on their wheels. All the weights are on the inside so it is a little tough to see. Anyone else in the same boat?

 

Tire tire pressure sensors also add to the mass of the wheel.

 

The tire sensors weighs about 3 onces. There is a machined area on the wheel where the sensor sits. The material removed for the sensors weighs the same as the sensor. So I know it's not that. Plus I just had a set of BBS wheels with sensors mounted up for my Tacoma. They took less than 1 once of lead to balance a 33" all terrain tire. It's the wheels.