Hey guys.

How would one test a speedometer to see if its actually reporting the proper speeds.

When I am doing 50kmph it feels like I am rolling at 25 or 30 and people are passing me like I was parked. I am not sure if the speedo is off or maybe the fact tat I drove the tempo for 3 years before the TransAm and the Tempo sits higher. I just want to make sure that the speedometer is reporting the proper speeds.

Thanks

 

a simple but not perfectly accurate way is to find a friend with a new car and cruise control. make sure his car is factory stock, and have him cruise at a certain speed. then just see if your car's speedo is showing the same speed.


there is prolly a more technical way to do this, but the above way will prolly git-r-done

 

You only want to do this if their car is newer and has a fully electronic speedo that recieves pulses. If not than you will be basing your speedo off another inaccurate speedo. our speedos are way off. The fatser you go the worse they get. Find a raod that has one of those radar trailers and match it up to that.

I would just refer your old friend math. As long as you know your rear tire size, cruise gear, rear end gear and rpm you can find the exact speed you should be traveling.

 

up here we don't have those trailers with the scopes. They are too cheap to get that kinda technology so instead they pay the police to sit on the highway with a radar gun and blast cars as they go by.

Times like this I wish I knew a cop with a radar.

 

It is much eaiser and safer to compute it on paper and then compair it to your speedo readout.

 

Do you live near an interstate with mile markers? If so you can verify it is accurate by using your odometer and verifying that one mile on the interstate is one mile on your odometer(or trip meter for that matter)

 

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Can I get the equation to figure this out mathematically?

 

tech equations

 

If you are driving at a constant 60MPH the odometer should click over one mile every 60 seconds. The two work together and get the same feed from the VSS.