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-   -   speedometer calibration for 3rd gen (https://www.rx7club.com/3rd-generation-specific-1993-2002-16/speedometer-calibration-3rd-gen-22619/)

rx7pimp 09-25-01 07:11 PM

speedometer calibration for 3rd gen
 
Can anyone tell me the best way to calibrate speedometer in my 94 3rd gen. Or let me know how fast you speedometer says when you are at 1000 RPM

alwan16 09-25-01 07:28 PM

at 60mph in 5th you will be at 2500rpm with stock wheel and tire sizes. that's the easiest way to do it.

3GRX7 03-07-07 06:27 PM

^ Is this calculation accurate? Does anyone know what the formula might be with 18" rims?

unnerv 03-07-07 06:33 PM

wheel size does not make a difference, only outside tire diameter.

rajeevx7 03-07-07 06:41 PM

When you take your cluster apart, there are printed equalities between MPH and RPM right on the guage face. But, as stated earlier, this is with stock sized tires.

3GRX7 03-07-07 06:44 PM

OK....well, I have 18" rims with 35's in the rear & 40's in the front. Is it based on the front or rears?

Also, the printed formula on the speedo says: 60 MPH= 1024 RPM. The question I have is at what gear? And how do I adjust for my rim & tire sizes?

Thanks,

Ian

antiSUV 03-07-07 06:53 PM

You also need to give the section width. The 35 and 40 numbers have to be used as a percentage and multiplied by the section width to determine sidewall height.... In other words, if you are running 265mm section width tires in the rear, then the sidewall height is 0.35 x 265mm = 92.75mm = 3.65in

So....(18in wheels + (3.65in x 2)) x pi = 79.48in rolling circumference.
Which I know isn't your question exactly, but I'm trying to show how the numbers on the sides of your tire actually work.

-James

unnerv 03-09-07 12:09 PM

You can use this calculator to compare tire sizes and how they affect the speedo
http://www.miata.net/garage/tirecalc.html

DamonB 03-09-07 12:20 PM


Originally Posted by rx7pimp
Can anyone tell me the best way to calibrate speedometer in my 94 3rd gen. Or let me know how fast you speedometer says when you are at 1000 RPM

If you're comparing the speedometer to the tach you'll get the same speed vs. rpm no matter what size tire is on the car. The speedometer has no idea how fast you're actually going, it only knows how fast the driveshaft is turning.


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