Why dangerous? Honestly, the better shops in my area do it this way. Some people complain about balancing, air pressures, etc., but last time I put new tires on my X5, I had them balance them on-car and paid an extra $40 for nitrogen. 40k miles later I haven't had to add nitrogen/air once and have never had a vibration issue.

Tire shops are hit and miss. Even national chains, but this place is know to be money. A little more expensive, but they do little things like wash your wheels and hand torque your lugs when other typical chains air gun them up. No other local tire shop has Lambo's, Ferrari's, Bentley's, Porsche's, MB's, Bimmers, etc. lined up like this place.

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Profeshenal spellar