If it’s scary to drive because of handling then your suspension and/or steering need attention. It should only be uncomfortable due to wind noise, rain leaks, and lack of adequate heat - the classic experience. That said, they were never designed for hours of miserable American freeway driving, or safety at those speeds. Crash in a Defender at 70mph and there’s a good chance you’re done for.
Which cap and rotor are you using? There’s only one good option anymore. The guys here will recall the name.
