Dokatka worse than conventional spare tire?

Most modern cars equipped dokatkoy rather than a full spare wheel. There are many reasons - layout, a desire to increase the boot, no need for a spare wheel on European autobahns and. etc. It is important to remember that dokatka - this is not a complete wheel. Diameter less pressure is greater. Accordingly, the following problems: reducing the area of ??the contact patch with the road. It is fraught with a sharp deterioration in governance and a marked increase in stopping distance, increasing the difference in angular velocities of the wheels on one axle, installed dokatka. As a result, the differential falls increased load, the failure of electronic stabilization systems - ESP, ABS, and. etc. In the case of dokatki, electronic perceived decrease in diameter as slippage, much greater risk of damage than a full wheel. At high pressure and small width dokatki is obvious. All these problems are exacerbated by the growth of the difference in diameter between dokatkoy and other wheels. If dokatka not much less than the other wheels, it is obvious that we can neglect the difference between angular velocity and not worry about differential. In addition, in this situation the electronic system is often continue to operate successfully, improving the car's behavior with dokatkoy under braking and cornering. If the difference is greater (eg 14 "and 17"), the electronic system should be sure to disable. If you do not, you should expect a permanent locking the wheels on the axle, installed dokatka. "Brain" of your car will seem that the wheels are rolling on the surface with a different coefficient of adhesion. When a large difference of diameters is obvious that the load on the differential will be increased. You can roughly estimate the increase of the load as the square of the difference of diameters and vehicle speed. As a result, in such a situation riding dokatke at a distance of more than 100-200 km and at speeds exceeding 70 km / h would be detrimental to your car. However, even if the difference in diameters is small, we should not think that dokatke can move normally. First, the tread depth dokatki intended only 2000-5000 miles. Secondly, the speed of a car with dokatkoy more than 80 km / h is dangerous in any way. Third, the increased braking distances. Fourth, the behavior of the car when cornering can become unpredictable. In order to minimize these negative effects is to install dokatku the rear axle. Especially if the diameter is greater than the difference. In this case, the stopping distance (at least on the pavement) would remain within the limits of your expectations. If your car is front wheel, then the danger of drift decreases. True, the increased risk of skidding, but in normal circumstances it would be easier to overcome. In addition, if front drive can not be afraid of and for the differential. If we talk about rear-wheel drive vehicles, here the emphasis shifted somewhat. If it is important to preserve the stopping distance, you should follow the above recommendations. If it happens in winter, and the car has winter tires installed, with the wheels - the ice, the driver would be easier if dokatka will come. In addition, the winter is better to move with a minimum speed, not shutting down the system stabilization, despite their inadequate work.