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Speedometer correction factors

Indy555

Re: Speedometer correction factors

Post by Indy555 »

petroscf wrote:Indeed!!
And based on a couple of comparisons I've done with gps, it seems you're right!
However, isn't all this also depending on wheels diameter?
Yes. You're right. But most wheel dimensions that fit the e21 are comparable in scope.
So it's correct to have always an eye on the factory fitted wheels for Your e21...

175/60R13 : 1.63m
185/60R13 : 1.67m
185/50R14 : 1.63m
195/45R15 : 1.68m

Just a few....



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Re: Speedometer correction factors

Post by petroscf »

My car initially, as a 316 used to wear 165/13 which means I guess a profile of 82? Or 80?
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Jeroen
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Re: Speedometer correction factors

Post by Jeroen »

Stock size is, I believe, 185/70-13, diameter 589mm, or 165R13 (80% sidewall), 594mm in diameter
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Re: Speedometer correction factors

Post by petroscf »

mcjjordan wrote:found a lovely calculator for working out variants

http://johnmaherracing.com/calculators/ ... alculator/
As this is really lovely, shouldn't we add this to the "all kinds of useful calculators" thread, perhaps?
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Re: Speedometer correction factors

Post by Jeroen »

We had one in there but the link was now dead so I put this one in, thanks!
Regards/groeten, Jeroen

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Re: Speedometer correction factors

Post by petroscf »

:thumbsup
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Re: Speedometer correction factors

Post by petroscf »

Jeroen wrote:We had one in there but the link was now dead so I put this one in, thanks!
Today tried a couple of times to reach this link, it doesn't seem to work, hope it is only temporary
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Re: Speedometer correction factors

Post by petroscf »

Found this one instead, seems ok:

http://www.cargister.com/calculator-gear-ratio
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Re: Speedometer correction factors

Post by Jeroen »

Thanks I'll update the link once again haha
Regards/groeten, Jeroen

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Re: Speedometer correction factors

Post by petroscf »

The speed correction factor should be taken into account when calculating the distances shown on the odometer?
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Re: Speedometer correction factors

Post by petroscf »

petroscf wrote:
Fri Sep 08, 2017 10:46 am
The speed correction factor should be taken into account when calculating the distances shown on the odometer?
Coming back here with -almost- the same question:

Speedo and diff are matching (0762 and 3,45). Comparing to speed counting apps on the phone working with gps the speed numbers seem to be pretty close.
However, the car's odometer seem to count km faster than the gps app. So for about 100 km I get like 110-112 on the odometer (not 100% sure of the exact numbers I have to re-check this to be sure)
Who to believe?
Could my speedo have inside it an odometer from another car? Or might someone have replaced something inside (a worn gear for example) and put a wrong part?
I am now gathering some parts and then I will have the diff replaced for a 3.64 as it finally seems better for the engine's torque, and the speedo will also be replaced by a 0808 (from 320/6), in order to match. I am waiting to see what happens with that speedo's odometer and then I will come back here.
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Re: Speedometer correction factors

Post by BertjeConti »

Apps on phone use gps signal and are very acurate in counting kms.

Wormwheel in gearbox have always the same ratio for all gearboxes with speedo cable.
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