The car rental companies will tell you not to travel around West Maui's rugged north shore. I've never figured out why. Although narrow and winding, the road is paved the entire way. Perhaps the problem lies more in the fact that if you were to break down, getting service would be hard plus the road can be dangerous in bad weather with flooding and falling rocks.
The drive itself is absolutely breathtaking, in some ways more impressive than the Hana Highway, which gets much more publicity. From Kapalua to Wailuku you pass some of the most rugged coastline in the world and some very lovely beaches and bays which are not well known or frequented.
The drive itself can be done in a couple of hours without stops. In order to really appreciate the views, however, it will take you between four and five hours.
Driving past Kapalua on the Honopi'ilani Highway the road will begin an upwards climb. Past D.T. Fleming Beach Park you'll come to the Mokuleia Marine Life Conservation District and Mokuleia Bay at mile marker 32. You'll have to park along the road and walk down a long stairway to get to the beach below, but it's well worth it especially if you like to snorkel. Be careful of high waves and rough surf in the winter,
The small, sandy beach here is nicknamed Slaughterhouse Beach, not because it's dangerous, but because the Honolua Ranch, which sits above the bay, once had two slaughterhouses on the ridge. The slaughterhouses were torn down in the 1960's but the name remains.