I've been wondering about the accuracy of my speedo ever since I reported my fuel gauge problem (which is supposed to be fixed, I'll find out soon enough). Somebody said that it's be running much faster than actual.

So here I am, yesterday, going down Windward Parkway (those in Atlanta will now it's a regular speed trap), round one of the bends and there he is - Mr. Policeman. Quick speedo check while simultaneosly hitting the brakes - I see 60mph and I'm in a 45mph zone What does the cop do? Bugger all. So now I'm really thinking my speedo is off.

Anyway, I turn around and went to see the cop. Parked next to him, windows open, he seems pretty cool and approachable. I asked him if he wouldn't mind hitting me with the radar if I turned around and went by him again so I could check my speedo. He said normally he'd love to but this was the one day his radar had broken on him and he couldn't use it <img src="graemlins/roflmao.gif" border="0" alt="[hiha]" />

So I'm still none the wiser and it might explain why he didn't budge went I rounded the corner at 60mph..or was it 50mph...?

 

maybe he didnt budge 'cause his radars broken.

 

An easy way to check you speedo is to get out on an Interstate that has mile markers, hopefully on a fairly flat stretch where it is easy to maintain a constant pace. Run at a steady 60 mph for 1 mile and time yourself with a stopwatch. If the speedo is deadon, it should take exactly 1 minute to travel a mile at 60 mph.

To calculate your actual speed, divide 3600 by the actual number of seconds that it took you to go one mile. This will give you your speed in mph and should give you an idea of how accurate your speedo is.

Karl

 

That's what I do, Karl. I've found that with a run of 20 - 30 miles you can get an accurate reading.

 

I find the speedo runs a bit on the high side. The lack of accuracy is a known issue... just wait to see what it does to your odometer.

 

[quote]Originally posted by Sloth:
<strong>I find the speedo runs a bit on the high side. The lack of accuracy is a known issue... just wait to see what it does to your odometer. </strong><hr></blockquote>

Any idea how fast?

 

Find a friend with a handheld GPS. It will tell you exactly how fast you're going and if the speedo is off.

I've checked mine and the digital is spot on.

 

[quote]Originally posted by aen:
<strong>Find a friend with a handheld GPS. It will tell you exactly how fast you're going and if the speedo is off.

I've checked mine and the digital is spot on.</strong><hr></blockquote>

aen - you're assuming I don't have one

Great idea my friend, I'll try it later on with the one that I use for my plane.

 

Look in you owners manual......

You should have a chart...RPM to MPH in a particular gear....If not I'm sure we can all help you by posting our speeds in (say 3rd gear) for 3K 4K and 5K that should make you feel that your ok.

Do you have stock size tires?????

 

Thanks Armando.. I'm going to do the GPS thing tomorrow.

 

Seconds/ = True MPH
One mile

50 = 72
51 = 70.6
52 = 69.2
53 = 67.9
54 = 66.7
55 = 65.5
56 = 64.3
57 = 63.2
58 = 62.1
59 = 61
60
61 = 59
62 = 58.1
63 = 57.1
64 = 56.3
65 = 55.4
66 = 54.6
67 = 53.7
68 = 52.9
69 = 52.2
70 = 51.4

(formatting's kinda buggered...)

 

I did the test with my GPS .. i'm always a bit up of what indicates the speedo in real time.. about 6-7 Km/h.in miles: 3,78 to 4,35 miles.