WHEEL MAINTANANCE, EUWA SOUNDS THE ALARM!
Association of European Wheel Manufacturers
A survey directed by the Association of European wheel manufacturers has recently brought to the surface a number of wheel repair and reconditioning practices blatantly in violation of current regulations, which pose a serious threat to safety: here is what everyone should know
Mino De Rigo
City streets resembling a Gruyere cheese, full of holes, pavements with unnecessarily sharp edges, killer speed bumps. Whoever has not had a damaged rim, please raise your hand; and you do not even need to drive in violation of traffic rules. Here then is the dilemma: Should I fix it or ignore the damage? Who can I trust? And how much will it cost? The customary address is the nearest tire dealer, ready to address the motorist’s concerns and solve the problem by sending the rims to a repair specialist.
Not all wheels, however, can be repaired, and even repair procedures are not all the same. "In other words - says Giorgio Muffatto, vice president of the Technical Commission of EUWA, the Association of European Wheel Manufacturers - there are acceptable wheel repair and reconditioning practices, while others should be avoided at all costs. Assuming that the tire dealer, relying on the expertise of wheel repairing specialists, will not question the procedures involved, it is appropriate to clarify what is allowed and what is not".
Let us start by saying that wheel manufacturers produce wheels as original equipment following the technical specs provided by vehicle manufacturers and in the certificate of conformity, the component’s ID, so to speak, where technical parameters such as fatigue resistance are included.
Deformation and cracks, improper practices
"A concern that appears to be largely overrated as it deals with a theoretical mileage of 300 thousand km. And nowadays cars hardly come to that, all the more so considering the double set rules for winter tires". All is well then, at least until there is an impact. The wheels that are most likely to be damaged are those boasting large diameters with low profile tires, since manufacturers are committed to making them lighter and lighter, as they are often intended for sports cars and high-end sedans. The same applies to wheels for run-flat tires, which cause more stress on the rim-well compared to traditional tires, as the load is distributed differently. Muffatto explains: "In the presence of a hole or a speed bump, wheels of greater diameter equipped with low profile tires and lower air pressures than recommended may damage the inner edge of the rim. These small deformations, normally around a millimeter, do not affect the vehicle’s handling, neither do they cause any vibrations to the steering wheel, but in the long run they may develop into cracks and give rise to a progressive loss of air pressure.
Cracks normally form on the edges around the tire bead, and as time passes and miles are driven, they can easily become through holes”. He adds:" The customer should be told that the standard wheel is covered by the manufacturer‘s warranty. But this is lost in case of an improper repair procedure. Any welding is tantamount to putting a patch, and could further aggravate the situation. But above all this is inadmissible, since it changes the properties of the metal and, with them, the characteristics of strength and durability guaranteed by the production process”.
No straightening allowed
To understand what is happening on the market, EUWA specialists have conducted a survey visiting some repair companies. "The result - stresses Muffatto - was rather bewildering. From soldering two parts into one to rebuild a damaged wheel, to trimming the rim-well, a sort of grinding that no longer respected the specs for the correct wheel/tire combination, not to mention that the material eliminated thinned the edge where the tire bead is lodged, and the burned spots here and there testified the attempts to straighten a rim through heating and beating. Again, any system that induces strong thermal variations on the metal, thus changing its characteristics, is completely illegal. That is why a bent rim must simply be thrown away". In short, forget about using hammers and hydraulic jacks. While such practices may not directly translate into a safety risk for the vehicle, they certainly do not return an undamaged product; if not harmful per se, they appear to be at least unnecessary. At the moment, no studies have been made on these types of “repairs” that analyze in detail, both scientifically and on a sufficiently large scale, the consequences of such unorthodox practices. Since this is a business that one would imagine quite lucrative, some prosper in total violation of the rules. “Whoever repairs and/or reconditions wheels – observes Muffatto – should not only declare his being qualified to do so, but should also place his brand or logo on the work done so as to provide a proper work guarantee. Something that no one has admitted doing, placing the responsibility squarely on the client’s shoulders. Not to mention that the majority of reconditioned wheels would have been eventually fitted on cars destined to fairs and exhibitions”.
Magnesium wheels are off-limits
Other purely aesthetic operations, such as repainting and diamond grinding, are permissible provided they are not followed by a subsequent passage of the wheel in the oven. "It would be enough to use two-pack protective coatings, so that thermal characteristics and safety are not adversely affected. Of course, if the pre-treatment of the edges is not properly performed, a thread-like corrosion will be generated over time and in harsh environments, a kind of spider web which dims the luster that was supposed to be restored”. As far as sandblasting is concerned, or alternatively shot peening, the green light is unconditional. "Especially if -says the Vice President of EUWA Technical Committee - applied over an area subject to fatigue, since it improves resistance due to a compacting effect on the surface of the wheel". So far, procedures on standard aluminum wheels were discussed. But what if it comes down to magnesium wheels? "Repairing these is even more dangerous, since this metal is more delicate than aluminum and much more sensitive to the variation of the parameters of resistance to fatigue. So much so that as original equipment, it was decided to raise the corresponding thresholds of magnesium wheels, since the increased breaking load drastically shortened, as a result of heat accumulation, the life span of the wheel". Racing cars aside, magnesium wheels are seen almost exclusively on historic vehicles. However, today’s evolution, which leads in the direction of thinner and lighter wheels, can only make certain repairs procedures even riskier.
A SMART WHEEL WITH AN ELEPHANT’S MEMORY
Similar to and yet more than self-repairing paint, thanks to a particularly elastic resin, the dream of a wheel capable of absorbing any impact and returning independently to its original state could soon be a reality. Since the spread of hybrid and electric vehicles is creating a new generation of wheels that are thinner, lighter, larger in diameter and mainly manufactured using new materials, interesting new developments in this area are expected. Thermoplastic resin wheels, for example, have already been presented in prototype form, very sturdy yet very light. Seemingly less complicated to repair than carbon wheels (or hybrid wheels, with a composite fiber rim-well and the inner part in aluminum) currently under the lens of many manufacturers.
The advantage of extreme strength and lightness is contrasted by a higher risk in the event of a collision, which triggers the possible delamination of the layers and the literal explosion of parts of the wheel, without prior warning. Needless to say that wheel repairs, in this case, would be almost exclusively performed by the manufacturers themselves. The smart wheel, though still not quite self-repairing, is fast becoming a reality: advanced aerospace technology and memory retaining materials, allow the wheel, through a suitable system, to communicate all the information it records simply by going close to it with a smartphone, and visualizing all the details in real time.