The 64-year-old man was pronounced dead at the scene on the A41 where the quad bike he was riding had overturned.
He is understood to have been overtaking a line of traffic when he was involved in a collision with a Ford Fiesta which was turning right into a petrol station, West Midlands Police said.
The crash happened next to the BP garage in Warwick Road, near Olton railway station, at 8.30pm on Thursday.
The driver of the Fiesta, a woman, stopped at the scene and although shaken up did not suffer any serious injuries. She has been helping police with their inquiries.
Nearly a mile-long stretch of the A41 was cordoned off on Thursday evening as specialist collision investigators examined the scene around the two vehicles.
Detective Sergeant Paul Hughes, from the Serious Collision Investigation Unit, said: “This is a tragic incident and our thoughts go out to the victim’s loved ones who are being supported by one of our specialist family liaison officers.
“The driver is assisting with our enquiries and our investigation is underway as we piece together the circumstances of the collision.
“We are appealing for anyone who witnessed the collision, or with dash-cam footage, who has not already spoken to us to come forward.”
The quad bike involved was a Taiwan Golden Bee (TGB).
A West Midlands Ambulance Service spokeswoman said: “Crews arrived to find the quad bike rider, a man, in a critical condition.
“Staff worked quickly to administer specialised trauma care to the patient. Sadly though, despite the best efforts, nothing could be done to save the man and he was confirmed deceased on scene.
“The driver of the car, a woman, was treated for minor injuries and discharged at the scene.”
Anyone with information is asked to email firstname.lastname@example.org or use live chat on the police website quoting log 3592 of July 15.