So my new tires (215/50/13) are the same rolling diameter as the stock 12's but my speedo seems tobe way out of sink. Here's what I've come up with when doing 30 mph my speedo reads 40 when doing anything above 50 mph the speedo is off by 20 mph. So when doing 50 my speedo reads 70 and when doing 60 the speedo reads 80. Is there any way to fix this? Can I get the speedo re calibrated?

The speedometers are often 10% off.
What you need to determine first, it how accurate the odometer is. Then you will know if you need to change the gear, or just the dial.

I just checked mine today. Drive down the highway for 10 miles, and watch the mileposts on the side. At the first milepost, note the mileage. At the 10th, note it again.

My odometer is is 5% off. So fitting the next speedometer gear (6% change) will make it very close. After that I will time the speedometer and see how close to reading correctly it is.



Speedometer calibration

Thanks David I am heading out right now

Ok here's my trip reports Ddgonzal

TRIP 1:
Start: 19977.6
1: 19978.7
2: 19979.7
3: **missed it**
4: 19981.8
5: 19982.8
6: 19984.0
7: 19985.0
8: 19986.1
9: 19987.1
10: **Missed it**
(I think I messed the first trip up some where)

TRIP 2
Start: 19990.9
1: 19991.4
2: 19992.4
3: 19993.5
4: 19994.6
5: 19995.7
6: 19996.7
7: 19997.8
8: 19998.8
9: 19999.9
10: 20000.8

So from what I can tell my Speedo reads the mileage correctly but is off with the MPH. So how do I calculate what Speedo gear I need? Thanks again for the Help Ddgonzal

Your odometer is off 5% (0.5 off after 10 miles). So changing the stock 17T gear to a gear one tooth different is called for (see Speedometer#Drive_Ratios). Then it should be about 1% off the other direction. Which would be better than expected.

So it is reading slow. Says you only go 95 miles when you really go 100. After the gear change I estimate it will say 101 for every 100.

Now the MPH is also incorrect, off by a lot more than 5%. So a needle adjustment is called for. This is tricky to do because it's easy to make it worse and I've only done this once. I would remove the needle, put it back on about 7mph different. But you need to hold the shaft still when you do this. Very easy to break it. If you want to try it, like this:
1. Remove dash. See Dashboard removal
2. Unbolt speedometer
3. Carefully bend back the tabs that hold the center cap over the needle (center of speedo). Remove cap
4. Move needle to 30 MPH and hold it there with needle nose pliers
5. With your other two hands, carefully wiggle needle hub until it comes off
6. Assuming shaft hasn't moved, put needle back on at 23 mph position
7. Test

Hopefully it will read OK now at 30mph (with gear changed). Now if it is OK at 30, but off at 60, we'll have to think about this some more...

Don't trust me here. I've only done this once and my speedo though slightly better is not reading right yet, specifically it doesn't go all the way down to zero.

Any experts out there to give us a hand or more ideas?

Cool thanks David I will do that tomorrow after work. As for the gear your referring to the Cog gear in the trans right?

EDIT: Ok so I looked threw the gear replacement info and you said I need a 17 tooth also I tried RockAuto but they didn't list one any other places?

Nissan has them. 17T is stock.
Pull yours and count the teeth. Then get one tooth differ.

Oh lol I thought I needed a 17 tooth one ok will go pull it now and call Nissan dealer tomorrow