Recoding Speedometer

[theoldseacaptain]

Has anyone managed to successfully re-code their MK4 speedo using VCDS to keep it accurate when fitting larger tyres?

I am needing a little extra ground clearance temporarily to get down a rutted track, so looking at swapping to taller profile tyres but that would increase the rolling radius by 8%. That pushes it well outside factory tolerances. Ive seen a couple of "boxes" that you can fit between the sender and dash to alter the pulse signals but don't want to mess with wiring or have something permanent.

As these clusters seem to be on lots of models, thinking there must be a way of telling it what size of tyres are fitted??

Thanks

[Giddy]

I have an option to change +/- 5 mph form MFD menu on mine. That's how it came from factory. Guessing it should be an option with VCDS too.

[theoldseacaptain]

Isn't that just the Winter Tyre speed alarm?

[Giddy]

There is other option called 'winter tyres' too.
I thought +/-5 mph is for correcting the speed, but you might be right

[BenXCIV]

Yeah I also thought this setting allowed us to adjust the speedo, but I was equally disappointed when I realised it was just an alarm

[theoldseacaptain]

So, a bit of fiddling around with VCDS at lunchtime has found the measuring value blocks that show the tyre circumference and impulses per KM expected. Then found that you can adapt the cluster coding to different models, which in turn alters the impulses per KM and tyre circumference.

I changed mine to Tiguan which altered the impulses per KM from 22188 to 20440 and circumference from 1938 to 2104. Now these circumferences are both 50mm shorter than WTF show for the tyre size, so presumably how they build in the factory variation.

I don't have any means to test this at the moment and the Van isn't going out in the snow. Anyone else tried this?

[Pradcad]

Did you ever get to the bottom of this mate? Also needing to alter my speedo. Mines a mk3 however.


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[theoldseacaptain]

Worked fine for me. Tested with those roadside radar speed indicators and was getting near enough the same speed shown -vs- indicated with the 215/65/16 coded to Tiguan as 205/55/16 that was standard and coded to Caddy so still have that slight over-reading that they come with from the factory.

This may have been specific to my highline cluster (2016) so would recommend some testing / measuring to check its accurate on your cluster.