Speedometer Accuracy

[89Red240]

I'm new to the forum. I recently bought an '89 240sx hb 5speed. I have done my research on the s13 and decided to make it my next car when the right deal came around, and finally it did. I love my car!

I have a question about the speedometer on my new car. It seems to me that the speedo reads a good 10+mph faster than my actual speed at freeway speeds. I haven't had a chance to run side-by-side on the freeway with a buddy to compare speedo readings but I've driven the same way to work for 3 years and my speedo says I'm doing 75-80 to keep up with the traffic in the slow lane which is usually 65-70mph. The car has 205/60/15's on the stock wheels which the sticker in my glovebox says is the right size. The car is completely original and I have no reason to believe the diff. has ever been changed out so I assume the gearing is stock.

I can't think of anything else that could cause the speedo to be that far off. The needle doesn't bounce so I don't think there are any speedo cable problems.

Any ideas?

Thanks,Brandon

[navysnail]

do a run-by-side first, before comparing. it may just need calibration.

congrats on the new car

[89Red240]

"it may just need calibration"

How do I calibrate my speedo?

Brandon

[guyaverage]

I started a thread about this exact same problem in the online mechanic section. This is the second 240 I have had (both 1993's) that reads 7-10 mph too fast. My first one I took to a speedometer shop, they put it on rollers to calibrate it, put in a different speed sensor drive gear, and lightened my wallet about $50-$60 (I forget the exact amount). I sent the bill to the Nissan dealer where I bought it and they actually paid it (Not until after an unpleasant confrontation with the service manager....I had taken it to them first, they claimed everything was fine and the speedo was 'right on'). I plan on taking this 240 in soon, being that the speedo is 7 mph fast at 70 mph means my 84,500 miles should really read several thousand miles less is what has me the most concerned. I'm just going to cough up the money and have it done. In my other thread I had asked if there was a way to calibrate it myself the answer was pretty much no, there isnt a magical adjustment screw anywhere to turn to change the reading.

[Phax]

I passed one of those highway radar units that tells you your speed so that you can slow down. My speedo said that I was ~110mph. The radar unit got me at 86.

[TurboKA37]

i dont think those things are very accurate at those speeds

[slo40]

My s13 says I am always going 5mph slower than I am actually going. Ohhh well better gas mileage I guess.

[drifter_for_life06]

phax yurs must be off a LOT, 110-86 thats insane, what is a speedo shop? can you just take the car to any garage? or does it have to be a speedometer specific shop?

[guyaverage]

Luckily there is a local speedometer shop right near where I work, but they arent just speedometers they do some other aftermarket stuff (cruise control, a/c, etc) but they actually have rollers to pull the car on to calibrate it. I dont know if or how other places do it.

[Candymans240sx1]

Brandon,

****( The needle doesn't bounce so I don't think there are any speedo cable problems.)****

There isn't a speedometer cable in the 240. its all electric for a sender on the transmission.I'm having my own speedo problems, so I figured that much out so far.

Jason

[Xneubien]

when i pass any of those highway side radars they always say that Im 5mph slower than my digital readout in my 240

[p00t]

for me:

3-5mph off below 65

5-7 off 65-85

10 or more off 85+

i hate it.