How often do you ask the Question: How long should this part last?

The question is asked in terms of many, if not at least all, service and maintenance parts of the vehicle. Before discussing the details of lifespan, it is important to place in context that the term service implies it has a time frame associated with it, i.e. there is an interval at which the item either needs to be maintained or replaced.

Naturally the progression assumes that the better the quality of the part, the better the capability of the part to perform its role in the service interval. In some cases it is expected that a part that costs more should last longer. This is true in some of the wear items in the vehicle parts mix.

But if we are to be clinical about this, the original vehicle manufacturer has set out either a time or kilometre related interval for a vehicle to be serviced and checked. This is based upon a variety of factors such as the component parts that have been specified for the vehicle, including lubricants and filtration, Sparkplugs, Brake Friction material, Shock Absorbers and many others. These all have different requirements in terms of replacement.

The service interval is determined out of an average kilometre per year/month figure which equates roughly to the serviceable hours a part can provide.

If one is to explore the engine for instance, the oil is being circulated rapidly and under high pressure and temperature the entire time the engine is running, at the same time the oil filter has to clean out the impurities and or any wear materials at the same pace. Now if the filter was merely left to continue for ever would it not become clogged (like a vacuum cleaner bag) of course it would, therefore it must be replaced to ensure free flow of oil for filtration. The same principle applies to the Airfilter which effectively is identical to a vacuum cleaner, only it is filtering the dust and particles before they enter the engine and cause excessive wear and tear.

When exploring the role of the Shock Absorber, this part is of such a critical nature to the stability of the vehicle that without it working effectively, numerous factors change for the worse in operating the vehicle. The braking distance is dramatically increased, cornering capability is diminished with the vehicle not being able to maintain directional control, and not least tyre wear is impacted on to such an extent that the tyre life can be reduced by more than 50% (which leads to another impending calamity). So why the fuss, the Shock Absorber is essentially a piston in a sleeve that goes up and down rapidly according the undulations and bumps in the road, this movement is restricted by either hydraulics or gas or both combined. It is this resistance that needs to be maintained for effective operation of the Shock Absorber. To put this in context the Shock Absorber could move as much as 2000 times per kilometre on a tar road, imagine on a dirt road. Therefore it is only obvious that there must be some degree of wear inside the Shock Absorber, which will naturally impact on its life span.

In a four stroke engine, Spark plugs need to fire on every fourth stroke or second revolution. So if one has to do a bit of simple maths. A four cylinder engine running at 4000 RPM means that each of the four sparkplugs must fire a spark 2000 times a minute, 33,3 times a second. Bearing in mind that each time a spark occurs a tiny piece of metal is eroded from the sparkplug casing. Again this provides sufficient reason for the wear and subsequent reduction in efficiency of a spark plug over time. In the event that the sparkplugs have become worn a number of implications arise from this, the stress on the ignition system is increased in order to provide a spark across a larger gap, the timing of the spark can be slightly off, leading to reduced power and increased fuel consumption, notwithstanding harder starting and eventual failure.

So with this all in mind we explore some of the original principles of replacement parts assuming these are the base level products and not the highly technologically advanced products using precious metals etc.

The filtration system should effectively be replaced along with new fluids at the 200 hour of engine operation mark. So how far is this in kilometres. If one assumes an average urban/suburban cycle at approximately 75km/h (allowing for 50/50 town vs freeway) then it stand to reason this interval roughly reaches the 15 000km mark.

Spark plugs would given the same assumptions as above replicate the filters at the 15 000km mark.

Where both of the above are limited to a time factor instead is where the driving cycle varies with more urban cycle hence a far lower average speed, in which case the hours of operation reduce the kilometre intervals accordingly.

Shock Absorbers fit into a slightly different category as they are directly related to the kilometres covered in travel. So where this is an interesting factor it is also relatively simple. The equitable rule of thumb for the lifespan of a quality brand shock absorber would not typically exceed the 80 000km mark. This is based on the volume of Oscillations per kilometre and the capabilities of the componentry used in the manufacture of the Shock Absorber being able to withstand the stress and wear.

Finally we will discuss the one item that is foremost on most motorist’s minds, how long do the brakes last. This is always an interesting question and is based upon the style of use. When exploring the style of use things such as:

  • Driving style
  • Towing
  • Vehicle mods
  • Suspension raised or lowered
  • Terrain of operation
  • Maintenance

Each of these above can have a negative influence on the lifespan of the brake system. However the single biggest impact on the lifespan of the brake system as a whole is related to the manner in which the system is maintained. If we explore this the following are guidelines to extracting the best from your brake system:

  • Always replace friction material on both sides of the vehicle whether front or rear
  • Always either skim (if within dimensions) or replace the discs or drums
  • Always flush and replace the brake fluid (it should be done at least every 24 months anyway).
  • Always clean the callipers properly especially the areas where the two parts slide against each other.
  • Ensure the wheel bearings are in good condition and the shock absorbers are not leaking (these two can cause Squealing of the brake system)

In conclusion this is by no means intended to be a definitive guide to the servicing of a motor vehicle but more so to highlight some of the reasons for parts needing to be serviced or replaced. If we were to provide a definitive guide of this nature we would need to compile a full book.

The details expressed above are opinion based and are in no way reflective of any on brand of product in particular, this is a generic look at parts in the industry as a whole.

Author: Hedley Judd, Director, TDAFA, MPEA, MIMA        Source: RMI