Do you think Im asking too much of my husband to back off the frequent visits with old girlfriend?

My husband of 15 years has been hanging out with his ex girlfriend. She rides a motorcycle..so does he..and they and lots of other people in the group too..have started riding on 10 or so hour trips. When the group cant make it..its just him and her. One time he took my son...and she took her grandson..they had a nice trip. Then she always wants something fixed in her house and calls..he goes right away to fix it. Now she wants him to ride up with her to her boyfriends house..about 2 hours away to fix something at his house. I have said it makes me feel uncomfortable and he screams at me that im crazy. I just think there are a million people other than her that he could become friends with. When I mention that it bothers me...he explodes and wont talk to me for hours. In the beginning of our relationship..she would call all the time and ask him to come back to her. I set her straight. then and really want to again.but I not sure if I should . Whos right? I really trust him...but I jut want him to hear me say..that if makes me uncomfortable ..should he stop? please let me know your opinions.