By definition, eating a tyre is an abnormal and accelerated wear of a tyre. Also, few people question tyre wear.
Did you know that what is considered reasonable in terms of a tyre’s service life varies considerably. Factors such as tyre load, speed, pressure, tread pattern, type of road surface, steering geometry, axle alignment, make of the vehicle and the axle the tyre is mounted on, and even the PH of water running on the roads, all affect tyre life. As a result, it’s nearly impossible to quantify normal wear relative to tyre life.
Every tyre-wear situation is unique, but it can be said, based on indoor tests, that if not for all the external factors, a quality PCR tyre might easily run to a hundred thousand kilometers or more.
Accelerated tyre wear is often a symptom of a hidden problem. It’s good to be able to identify a mechanical condition by the mark it leaves on your tyres. Simply replacing a worn tyre without dealing with the cause only ensures a premature retire for the next tyre you mount on. In most instances, switching brands of tyre won’t solve the problem, either.
There are differences in how different brands of tyre react to environmental influences. Typically, certain tyre brands and types are engineered to resist certain types of wear. Some do a better job at it than others, but the trick is to solve the root problem before it ruins the tyre. You can do that by having your tyre dealer analyze the wear to determine its cause. Given the multitude of possible culprits, here is an unscientific list of today’s top tyre killers.
This is the most common factor in prematurely ruined tyres. Tyre pressure check should take about twenty minutes in a month, but drivers seem more than willing to give up to about 12% worth of tread life for the 20 minutes a month.
Research shows that just 10% underinflation will shorten tread life by 9% to 16%. For demonstration, if we use an average truck tyre price of Ksh 45,000, underinflation could cost you up to Ksh 7,200 per tyre. Is 10 psi underinflation “close enough” to let the tyre go? It’s alarming how many tyres we find consistently underinflated when we conduct pressure check surveys at out shop.
It’s the air that carries the load, not the tyre; the tyre is just the containment device. If there’s not enough air to sufficiently support the load, the tyre’s sidewalls will flex more than they were designed for, and that flexing causes excessive heat buildup. Together, the weakening of the steel cords in the sidewall, and the softening of the rubber caused by the heat, can trim 15 percent off the life expectancy of the tyre.
It could also result in a “zipper” rupture, a circumferential tear in the mid-sidewall of a steel cord radial tyre, caused by the weakening of steel cables in the tyre’s sidewall due to running flat, (a tyre that has less than 75 percent of recommend inflation is flat).
The effects of heat and flexing due to under inflation are so dramatic that Rubber Manufacturers’ Association recommend that any tyre found to be 20% or more underinflated be immediately demounted, and inspected for damage.
20% under inflation won’t feel much different from recommend psi when you boot it on your pre-trip, so how are you supposed to know? Gauge it using a calibrated tyre gauge. Tyre inflation monitors are an ideal solution, and on a less expensive scale, good quality visual tyre pressure indicators won’t hurt.
Do you inflate your tyres to 35 psi because your pal does? You should use the load and inflation tables to calculate the optimum pressure for your application.
You don’t have to search hard to find examples of tyres literally vanishing in their owners’ eyes. Scrubbing and stresses on the tread caused by wheel miss-alignment or frame geometry are everywhere. Unfortunately, tyres often take the rap.
“His tyres ran out to 120,000 kms, but mine only went to 80,000, so I got a bad set of tyres.” Ever heard that one? You probably couldn’t count the differences between the trucks’ operations, lanes of travel, percentage of time on- and off-road, speed, load weights, etc. So how can you expect similar results in tyre life?
Tyres exhibiting accelerated wear are almost always responding to some external factor, such as wheel alignment. Toe-in and toe-out settings affect tyres dramatically, and while all tyres will exhibit the same type of wear resulting from an alignment problem, some weather it better than others, depending on the design characteristics of the tyres.
A few years ago, Michelin surveyed fleet take-offs and found that an amazing 78% of disposed tyres came out of service prematurely.
It’s tragic to see a Sh 50,000 tyre only delivering Sh 10,000 worth of life. Fleets have the advantage of observing tyre wear patterns that direct them to a problem. It’s not the same with one driver, one truck, and one set of tyres that lasts a year or more.
Mismatched Duals/Doubles on lorries and busses
Matching pressures is especially important on dual assemblies. An inflation mismatch greater than 5 psi means that the two tyres in a dual assembly could be significantly different in circumference – up to 150 mm. While that may not sound like much, because they’re bolted together, they have to cover the same amount of road in a single revolution. The larger tyre will drag the smaller one a distance of about 3 meters for every Kilometer, or 246 kilometers for every 100,000 kilometers on the clock.
Two more problems arise here: The “larger” of the two tyres in a dual assembly does more of the heavy lifting, causing it to wear prematurely, while the underinflated tyre runs hotter and doesn’t make proper contact with the road. Both cause irregular and premature tread wear – not to mention traction issues. Uneven shoulder wear usually appears on the under-inflated tyre, while center wear eats away at the properly inflated tyre. Don’t wait until the tread starts disappearing to worry about your tyre pressure.
While potentially the most difficult to manage, road hazard damage can be mitigated by driving carefully and ensuring proper repairs are made, when applicable. Cut and slashed sidewalls resulting from curb strikes can cause irreparable damage to the tyre, so inspecting tyres for this type of damage is important. Removing the damaged tyre reduces the risk of a future roadside rescue call, and a potential service failure.
Punctures are almost unavoidable, but proper repair procedures can preserve casing life. Have the driver well trained to minimize road hazards by driving carefully.