why do speedometers go as high as 140 – 160 mph but some average cars can’t go faster than 100 -120?
In: Technology
On the opposite side, when I was in high school, my parents had a car with a speedo that topped out at either 85 or 95 (pretty sure 85 – a ‘96 Mercury Sable).
I was curious what would happen if I went past that, and I immediately broke it. I never told them and let them discover it themselves.
I’ve noticed the end of the speedo would line up with redlining it in the highest gear. While physically impossible to do, it seems to be what they base it on.
All cars can do 120+ mph, going down an extremely steep hill, with “hurricane force winds” pushing it; even if the car isn’t turned on. There’s multiple alternative methods – being towed/pushed by race cars; being launched by catapult (like the aircraft catapults on an aircraft carrier), various modifications (e.g. getting an after-market turbocharger installed), etc.
The “alternative alternative” is if the car isn’t actually moving at all – e.g. on a device called a dynamometer where the car’s wheels sit on rollers; and the wheels can go faster than normal because there’s no wind resistance to push against when the car isn’t actually moving.
With a lot of engineering, you just shrug your shoulders, take whatever is realistic as a starting point and then say “let’s add 50% (or double it or…) to be safe”. A car that might only do 100 mph on a flat surface using its own power with no assistance and no modifications ends up with a 150 mph speedometer because it might be going downhill and/or might be getting assistance and/or might be modified.
For the same reason, a car that might only do 180 mph on a flat surface using its own power with no assistance and no modifications ends up with a 260 mph speedometer because it might….
Cars are also sold in other countries where they may use kilometers per hour instead of miles per hour. It’s easier to make one instrument cluster and just set the ones in the US to miles per hour.
This is not always the case with newer digital stuff or with speedometers with both units printed on it.
140 kilometers per hour is about 86 miles per hour.
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