The first pile-up happened on a curve in the road between the towns of Bad Duerrheim and Biesingen during the RiderMan event.
That caused congestion among the riders further back along the route, which lead to a second "mass crash", police said in statement.
Between 15 and 20 people were seriously hurt and had to be taken to hospital, but none of them was in a life-threatening condition, a police spokesman told AFP.
Another 20-25 people were taken to hospital for less serious injuries, with a further 35 or so treated at the scene.
Large numbers of emergency services and ambulances as well as four rescue helicopters were dispatched to the area in order to treat the wounded.
Police said that "an external cause can be ruled out".
The rest of the race was cancelled following the crashes.
The organisers of the RiderMan event had said that more than 1,200 people were taking part in the race on Sunday, which scheduled to be the last stage of a three-day event.
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