Abstract: In a brake disk for rail vehicle brake systems, a friction ring is made of a light metal such as aluminum (aluminum alloys), etc. to reduce weight. In order to reduce the weight further by approximately an additional 10%, the hub that supports the friction ring and is connected with the shaft of the rail vehicle is also made of light metal, such as aluminum. It is necessary to keep the temperature of such hubs below 120-140.degree. C. to prevent the shrink or press fit between the hub and shaft from loosening. To prevent such heat transmission, heat insulating layers are inserted between the inner circumference of the friction ring connected with the hub preferably by bolts. In the vicinity of the bolts, these layers can consist of insulating disks, insulating plates, or continuous insulating rings.