The Speedometer: A Tape Measure For Your Car

No part of a vehicle is so unimportant that it doesn’t deserve an article written about it. Having said that, today’s learning experience will have to do with the under-appreciated speedometer.

Such a simple machine you are saying and sure, compared to the transmission or the engine itself the speedometer is simple, but in truth it has several working parts that have to work in perfect harmony in order for the speedometer to measure accurately.

For the sake of conversation, the speedometer measures how fast a vehicle is travelling, whether it be in miles per hour or kilometers per hour. In almost all vehicles the speedometer is combined with the odometer and trip odometer so that the driver can tell how many miles the vehicle has travelled and even how many miles have been travelled on just one trip.

The speedometer is actually made up of a drive cable, a mandrel, a spiral gear, a magnet, a speedcup, hairspring and needle. And how does a speedometer work you might ask? Well, to accurately measure the speed of a car you either have to measure the speed of the engine or the speed of the wheels; in the case of the speedometer the speed of the engine and more specifically the transmission is measured by use of a cable wrapped around the mandrel and connected to the speedometer. It is actually a bit more complicated than that but you get the basic picture. When the vehicle moves the transmission is engaged and the speedometer measures speed.

The odometer measures distance by way of mechanical adjustments that designers make; usually one-thousand revolutions of the speedometer shaft will equal one mile on the odometer.

When the speedometer goes bad one of two things will happen: either it will quit registering speed altogether or it will register your speed as faster or slower than you are actually travelling. Either way you are begging for a speeding ticket if it is not fixed, and fixing or replacing a speedometer is a fairly simple process. The cost of an average speedometer is small and the replacement labor relatively easy; in other words, we ain’t talking about replacing a fuel pump or your suspension system. Grab your tools, do some research on the internet, and then save yourself some money by heading on over to your local self serve salvage yard. In Savannah the only place to shop if you are interested in quality used car parts is Cash-n-Carry, where You Pull it for great savings.