According to this page "The first Carrowdore 100 Road Race was held in 1927 on a 5.5 mile circuit which started on the Greyabbey to Millisle Road and continued down the coast road. However, after a crash at Newtownards in the Tourist Trophy Car Race the County Down Council banned all racing through built up areas and for the next two years the Carrowdore 100 was held over a circuit in the Comber/Killinchy area.
After World War 2, the Tourist Trophy moved to Dundrod, and after a couple of years the Carrowdale 100 moved back to Carrowdale, with the start in Carrowdore Village and went just outside Greyabbey and back to Carrowdore. The track was shortened over the years for safety reasons, now being 5.4 miles and with the start/finisg line at Ballyboley Corner."
The following photos are from the 1931 edition,