Q: Will these hold up on the street, or are sealed bearings only for track cars?

They are built for both. The bearings are sealed specifically so they retain lubrication and resist contamination, which is what gives spherical bushings long-term consistency on the road instead of wearing out quickly. The kit is described as optimized for spirited driving, track use, and alignment consistency. So a Model S or X that sees canyon runs and daily miles benefits from it, and the payoff is not reserved for a dedicated track car.