One can better understand the dangers which lurk when fitting tyres, if one knows the principle of the drop-center-rim. This is thus constructed, that the bead can only be pressed without problems over the edge of the rim, when on the opposite side, it is pressed into the deep-bed at an angle of more than 90°.
Let's have a look at it from the point of the more critical tyres, those with a cross-section of 45 or less. This will include Runflat-tyres, or those with a particularly high-speed index. Unfortunately, these tyres, where the demands made are presumably higher than the 'normal' tyre, are also the most difficult to fit, and the most sensitive.
In this case, differing demands collide with each other. Firstly, with these, mostly very wide tyres, the bead must be pressed into a deep-bed which is a good distance from the rim-edge. Secondly, the flank is actually too short or too stiff, to go over the rim-edge at this angle, without being damaged, and thirdly, under no circumstances may too much force be used.
Let's speak about temperatures. The, perhaps possible 15°C for normal tyres (see Tyre-Fitting) is distinctly too low for these tyres. Indeed, even normal room temperature is not enough. If necessary, they must be heated, however, not like in the Formula 1. Painting the entire bead with a suitable lubricant can also help. The protective covers, dealt with on the Tyre-Fitting page, must, once again be mentioned.
You won't have much success using the customary tyre-fitting machine. What you need is, on one side, a holding-clamp- or distance spacer to the rim-edge, while on the other side, the machine pulls strongly. By the way, modern machines nowadays have a force limiter, before the tyre is irreparably damaged, they will break off the action and urge you to take a different approach.
In this case, the operator is also more important than usual. He must recognise sharp edges, before they eat into the rubber. He must also be able to estimate forces, before they become excessive. For this reason, it may be advisable, if the tyre-fitting work-load is not too great, to have only one- or at the maximum two operators for the machine.
In addition, the human helper needs to have a good, clear conscience. Without a doubt, the parts to be mounted are pretty expensive, which could cause a tendency to hush-up possible mistakes, particularly as they are not directly visible anyway and sometimes come to light only after years of use. Indeed, if they do make themselves noticed, it could be very dangerous for the car passengers, and for other road users as well. 01/12