Here are recommendations from the official Sequoia National Park web site:
Vehicles Entering/Exiting Sequoia National Park via Generals Highway (the Main Road through the Parks) and Hwy 198
Vehicles longer than the recommendations listed below will likely cross the double yellow line. Drivers will be held responsible for any hazardous conditions caused by their actions. Follow the recommendations below for your safety and the safety of others:
•Vehicles longer than 22 feet (6.7056 meters) are not advised between Potwisha Campground and the Giant Forest Museum in Sequoia National Park.
•Vehicles longer than 24 feet (7.3152 meters) are not advised between the Foothills Visitor Center and Potwisha Campground in Sequoia National Park.
The section of the Generals Highway leading to and from the "Big Trees" in Giant Forest was built from 1921-1926. As a result, the road was not constructed to accommodate longer vehicles.
Here is another interesting web site for that same highway:
Edited: 9:21 pm, September 02, 2013