Originally Posted by
piper28
....Mauna Kea summit isn't a big deal, and could be done in a 2WD, but they don't want you to do it without a 4WD because it supposedly tears up the road more without it. I honestly couldn't tell you if that's true or not, but there's nothing real extreme about the road. I probably wouldn't recommend it if you've never done any mountain driving before though.
The issue with Mauna Kea is the steep descent through very thin air, which reduces braking effectiveness and contributes to brakes overheating and failing.
The road is too steep for even second gear as far as keeping the car moving at a reasonable pace...so 4WD with a lo mode is recommended.
Having said that, I've been to the summit when people have popped up in rental Mustang convertibles and minivans...