Those Ugly Alloy Wheels
Written by Dave McCracken; April 2, 2012 Share
In reality, alloy wheels add a certain aesthetic appeal to the vehicles they are installed on and most consumers prefer them for that reason. Alloy wheels are made from an alloy of aluminum or magnesium and are currently installed on more vehicles than not these days for reduced weight to improve fuel economy and better heat dissipation affecting the longevity of the tires, brakes and associated components.
The ugliness presents itself when you start to experience tires that are slowly losing air pressure over a short period of time. Alloy wheels have a clear coat of paint applied to them in the final production stage. The purpose of the clear coat is to help protect the alloy metals from degradation caused by moisture or minor impacts and abrasions. It also serves to maintain their appearance.
When the clear coat becomes damaged, it no longer protects the alloy metals from the effects of moisture. The clear coat separates from the wheel surface and moisture then will react with the alloy metal to form corrosion. This is especially true in areas that trap the moisture such as the bead area of the alloy wheel. When the bead area of the wheel corrodes, the corresponding sealing bead of the tire no longer makes full contact with the wheel. The corrosion will slowly expand and create a gap which then allows a small amount of air to escape. The following pictures illustrate examples of corrosion on the bead area of alloy wheels and the resulting effect on the tire. Click on each picture to view greater detail.
This condition further supports the need to regularly check your tire pressures. If your vehicle is not equipped with a Tire Pressure Monitoring System (TPMS), you run the risk of driving with under inflated tires. Doing so could result in a blow out or a severely damaged tire that requires replacement. When a tire is driven under inflated, the edge of the wheel will contact the inner casing of the tire causing internal damage. Notice the crumbled up rubber inside the tire below.
Ideally, we should all park our vehicles in a heated garage so any moisture will dissipate from the drying effect of the heat. But in the real world, a temporary fix is to remove the corrosion from both the bead area of the wheel and tire. The dimpling effect on the bead of the tire will usually require a sealer be applied to the affected surfaces to help fill in the gaps. Some wheels are so heavily corroded that machining or complete reconditioning of the wheel is required. You could also purchase new wheels if your budget allows, but either way, the tire should also be replaced. Reconditioning or replacing with new does offer a longer term solution to this problem. Below is an example of an alloy wheel after cleaning the corrosion.