The safety on roads depends, to a significant degree, on the technical condition of the vehicles that participate in road traffic, especially of their braking systems, whose adequate operation is a matter of critical importance. This particularly applies to the heaviest vehicles moving with high speeds, chiefly tractor-trailer and tractor-semitrailer units. Apart from correct functioning of the braking system of each of the vehicles being components of such units, the synchronization of braking of the vehicles plays a fundamental role in the braking process. The synchronization does not have to be checked during the mandatory periodical inspections of such vehicles being in service. This article deals with the problem mentioned above, especially if encountered in the case of older vehicles, as well as with the related adverse effects and possibilities of making appropriate corrections when any faults or malfunctions are detected. Thanks to technological progress, more and more vehicles are now provided with advanced electronic braking systems (EBS), where the problem of synchronization of the braking of vehicle combinations has already been solved to a considerable degree. Nevertheless, there are many situations that some minor adjustments might be recommendable even in this case. It is worth emphasizing, however, that for an appropriate correction to be made, adequate equipment and, above all, high professional knowledge and skill of the servicing personnel is indispensable.