Some car bike racks come with a maximum speed warning which shouldn’t be exceeded. Aerodynamic drag increases with speed, and exceeding the speed rating could exert too much force onto the bike cover. If possible, use a lower speed limit (-20 km/h) than is allowed for your bike rack (see your bike rack instructions). If your Bike Cover for car racks is made of the waterproof fabric, please note that the maximum authorized speed limit is 90 kph/56 mph and wind speed not exceeding 15 kph/9 mph. The vehicle’s speed must always be adjusted to the load being carried and the current driving conditions, such as the road type, road quality, wind conditions, traffic intensity and applicable speed limits. Also, the breathable and water-repellent fabric of our Bike Cover for car racks (except the waterproof fabric) allows it to dry fast in case you've caught the rain and creates less wind resistance during transportation. These are all important aspects to consider when transporting your bike.