Actually, the road into the Chisos Basin isn't the real problem (camp hosts are in big 5Ws and tour busses go to hotel); the tight quarters are INSIDE the campground. I highly advise parking out front and walking in first to look it over. Sometimes it's tight turns around boulders and sometimes it's the spur road with no turnaround and to get out you have to back around an uphill curve
Keep in mind that the CG was really built for tent campers. BTW, if its raining, I try to pick on of the sites that get slightly flooded so the tenters can have the dry sites.