Each sled consists of a main hull, a frame, a front and rear axle and two sets of runners. The hull, also known as a cowling, is generally constructed of fiberglass and made of two separate sections. The hull is mounted on four runners. The rear part of the bobsled must be open.
The driver steers the bobsled by pulling on two pieces of rope. These ropes are attached to a steering bolt that turns the front frame of the bobsled. Pulling on the rope in the right hand will steer the sled to the right; pulling on the rope in the left hand will steer the sled to the left.
The runners must be made of a solid piece of steel and no plating or coating is allowed. It is not permitted to warm up the runners, or use any substance that improves sliding. At the start of the race, the temperature of the runners is compared with a reference runner, which has been exposed to the open air for one hour prior to the competition. If a tested runner is too warm, the sled is disqualified. (Warm runners are not allowed because the heat would decrease the friction between the runners and ice, making the sled faster.)
Prior to the race, if teams wish to wipe their runners to remove impurities, they must use an official body of acetone that all teams share.
Women's sled (two women)
If the total weight of the sled, including crew, is less than the maximum weight, ballast may be added.
American driver Todd Hays described it as a "black art." The words "sorcery" and "black magic" have also been used when describing the "science" of designing and building bobsled runners. Most people involved with the sport acknowledge that the four runners are the most important part of the sled. That fact is somewhat obvious, even to outsiders, because the runners are the only part of the sled that comes in contact with the ice. The problem is that no one really knows exactly why good runners are fast or how to get them that way. "You could cut 20 sets of runners the same way from the same piece of steel," former U.S. driver Mike Dionne says. "And only one or two sets would be any good." No one really knows why those one or two sets are better than the other 18.
At first glance, the process doesn't seem complicated. The FIBT, the international governing body of bobsled, has stringent rules on how runners can be constructed. Each runner must be manufactured from a solid, homogenous piece of steel. They cannot be coated and there are very specific size requirements for nearly every dimension on the runner. All are round at the bottom. But that's exactly why the whole process is so mysterious. Sled builders have choices in how they cut them and some leeway with the shape, but in the end, everyone's runners look pretty much the same.
While they look the same, runners can perform quite differently. For some reason, whether it is chemical composition or shape, when runners interact with the ice, some create much less friction than others. In a sport decided by hundredths of seconds, the slightest reduction in friction over an approximately mile long section of track can be the difference between winning and losing. For many years, the elite bobsled teams in the world, such as Germany and Switzerland, had advantages over many of the world's other teams simply because they had better runners than everyone else.
In 2004, in an effort to create parity among teams, the FIBT instituted a rule requiring runners to be made of standard material produced by an FIBT-designated factory. The material is provided as a pre-machined section and the FIBT guarantees that all of pieces of steel are the same.
Only three pairs of runners per discipline (two-man bobsled and four-man bobsled) are allowed per pilot per season. Each runner is clearly identified to the pilot by the appending of a stamp with his full name. A complete inspection of the runners takes place at the beginning of the season and following this inspection, the two pairs of approved runners will be identified by an electronic stamp or by an FIBT stamp. A pilot has the option, once during a season, to declare a set of runners "destroyed." In this case, the pilot will be allowed, with the authorization of the jury, to introduce a new pair of runners, which will have to undergo the inspections mentioned above. Only one pair of extra runners can be introduced per discipline per season.
It costs teams thousands of dollars and hundreds of man-hours to design and test runners. But because of the uncertainty involved, good runners, once they are found, are priceless. Some drivers have used the same set of runners for years and in rare cases, good runners have even been used for decades. Pilots rarely let their best runners out of their sight. Most drivers keep their runners in their rooms with them, often locked in gun boxes. At then 2001 World Championships in St. Moritz, Switzerland, there were rumors circulating that some of the German sleds were using runners built in the 1970s. That was never confirmed, but the fact that people around the circuit even entertain the thought that the top teams in world were using runners that were over 20 years old is a perfect indication of their mystical nature.
Just as important as the runners themselves is picking a set of runners that is right for the track and weather conditions on the day of the race. Some runners perform better in warm weather, some in cold weather. One set of runners might work best on the track in Igls, Austria, but be almost worthless on the Olympic track in Vancouver.