ratios, slope of the terrain affect the overall speed of the rider. Bicycles designed for flat urban environments may have fixed gearing or three speeds and bicycles designed for hilly terrain, hauling weight, or traveling faster have more gears. In competitive cycling a sustainable high speed is augmented by the addition of more gears, using larger chainrings, lighter materials, aerodynamic design, and the aerodynamic effects of the peloton. The group can maintain a much higher speed over extended distance due to various cyclists taking turns at the head of the wind then dropping behind to rest. A team time trial produces the same effect. Modern cyclists use a speedometer or cyclocomputer to measure, record, and share several variables including speed, gradient, distance, time, cadence, slope, Watts, power, temperature, GPS data, route, and even heart rate. Cycling speed records The highest speed officially recorded for any human-powered vehicle (HPV) on level ground and with calm winds and without external aids (such as motor pacing and wind-blocks, but including a defined amount of gravity assist) is set in 2016 by Todd Reichert in the Eta Speedbike, a streamlined recumbent bicycle. In the 1989 Race Across America, a group of HPVs crossed the United States in just 5 days. The highest speed officially recorded for a bicycle ridden in a conventional upright position under fully faired conditions was over 200 m. That record was set in 1986 by Jim Glover on a Moulton AM7 at the Human Powered Speed Championships during Expo86 World Fair in Vancouver. The fastest bicycle speed in slipstream is 296 km/h (183.9 mph), set by Denise Mueller-Korenek in 2018 on the Bonneville Salt Flats. This involved slipstreaming behind a dragster. Cycling Speed Wobble Dangerous steering wobble may occur at high speeds, riding with no hands on the handle bars at lower speeds, and when the front forks are weighted with panniers. Reduction of weight and rotating mass There has been major corporate competition to lower the weight of racing bikes in order to be faster uphill and accelerating. The UCI sets a limit of 6.8 kg on the minimum weight of bicycles to be used in sanctioned races. Advantages of reduced mass For cycling on the level at a constant speed, a large weight reduction saves only a negligible amount of power and it is on the contrary beneficial to add mass in the form of aerodynamic improvements. But