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Old 09-08-2012, 09:59 PM   #1
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Speedo issue

Bought the car recently and the speedo is off by ten mph. u think the gears have been changed. Anyway to see whata in it. I have sct tuner which will reset the speedo just need to know whats in it. Help
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Old 09-08-2012, 10:02 PM   #2
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Gears or tire diameter is different than stock.

You can enter the tire revolutions per mile in the tuner. Go to the manufactures site and find out based on the size of the tire.

Small speedo differences are likely tire size (4-5 mph at around 50 mph). Anything more, likely gears.
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Old 09-08-2012, 10:03 PM   #3
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Lift up the rear end of the car, make a mark on the driveshaft, rotate the tire one full rotation and count how many times the driveshaft rotates. 3.55 rotations means you would have 3.55 gears etc. Stock should be 3.27s
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Old 09-08-2012, 10:52 PM   #4
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I think legally speedos can be off up to 10% from the factory. Speedos are off by % not MPH.

It's off by 10 mph at what speed? And what are you using to measure against? GPS indicated speed or a radar gun will be best to measure as other vehicles will be off also.

Also parts like speedo cables and gears can become worn depending on age and mileage. These parts and new tires that are the correct size could be factors.
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Old 09-09-2012, 09:31 AM   #5
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Its off by ten at all speeds. Using one of those cop thing like a radar that shows ur speeds
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Old 09-09-2012, 10:35 AM   #6
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With that being the case before I started changing things around I would get a second opinion or confirmation from another source to confirm that it's actually off.
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Old 09-09-2012, 10:52 AM   #7
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Do you have any radar speed signs? Those things seem to be pretty damn accurate. They usually have them around school zones or in residential neighborhoods that they don't want people to speed on. I'd drive by that signs at different speeds and write down what ur dash says and what the sign says. The signs look like this.

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I've seen signs that are 55 mph ones. This was the only good Internet pic I could find lol
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Old 09-09-2012, 10:58 AM   #8
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Quote:
Originally Posted by JetLife 01GT
Do you have any radar speed signs? Those things seem to be pretty damn accurate. They usually have them around school zones or in residential neighborhoods that they don't want people to speed on. I'd drive by that signs at different speeds and write down what ur dash says and what the sign says. The signs look like this.

I've seen signs that are 55 mph ones. This was the only good Internet pic I could find lol
idea
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Old 09-09-2012, 12:03 PM   #9
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If you have a smart phone, there are a ton of GPS based apps... Many tell you real time speed.
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Old 09-09-2012, 12:16 PM   #10
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I just need to figure out what gears I guess
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