However, most classic car bodies (manufactured before the late 1960s) did not include safety belts as standard equipment, and do not include readily available reinforced mounting points, on the vehicle body, therefore it can be problematic to install such equipment properly: specific studies and calculations should be performed before any attempts. Proper installation is critical, which means locating attachment points on the body/frame, assuring the strength by proper reinforcement, and following the seat belt installation instructions properly to reduce the risk of malfunction or failure. Some classic car owners are reluctant to retrofit seat belts for the loss of originality this modification implies. There have also been instances of cars losing points at shows for being retrofitted with seat belts. Fitting modern tires is also a suggestion to improve the handling. However, most modern tires may be much wider and have a lower profile than those used on classic cars when new, therefore they may interfere with suspension elements and the tire walls may become damaged. The suspension of a classic car may not be suitable for radial ply tyres, having been designed to only accommodate bias ply tires. Narrow classic car wheels may have been designed for narrow high-profile tube tires and not be suitable for modern tubeless radial tires. Another problem with modern tires on classic cars is that increased grip requires increased steering effort; many classic cars do not come with power steering. Many major tire companies have dedicated classic car tire marketing departments and will be able to give expert technical advice to address all these issues. It is important to know how radial tires will affect the performance of a car originally fitted with bias-ply tires, and the considerations needed to compensate for the differences. Upgrading braking using either bespoke parts, parts produced by the vehicle's manufacturer, from later versions of the same model or later models that may be compatible with minor modification, is an effective method of improving safety. Popular examples include drum brake to disc brake conversions, or adding a vacuum servo to cars with front disc brakes that did not originally have one. Although they lack such advanced safety features as air bags, antilock braking systems, and other electronic controls, most US-market cars built 1966 and later have basic safety features such as padded dashboards, seat belts, dual-circuit braking systems, and safety glass. Despite these concerns, classic cars are involved in significantly fewer accidents.