Speedometer Calibration

[pkt1213]

I couldn't find anything about speedometer calibration for the C5 except a thread for 2011. In it, it was said that rolling radius could be changed in the long code in module 17 using VCDS. I don't have that option in my 2003 S6. I would like to be able to correct my speedometer if possible. My HU does have GPS and it's not that far off. Just annoying.20201111_194636.jpg

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[Bordom]

IIRC there are only 3 possible options to change to. Regular C5 (A6, S6, RS6), Allroad, and something else.

I'd have to look it all up again to confirm

[pkt1213]

Thanks. I bumped up to a 255/40 18 so it's just far enough off to be annoying and maybe get me a ticket someday when I am not paying attention.

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[Mad Cow]

I think EEPROM modification is the only way, it's a bit of an involved process though if you're a first-timer. I've mapped out the EEPROM on my old b5, c5 should be the same thing just different locations for the various maps. Wouldn't recommend it unless you're comfortable with a hex editor or tunerpro/winols.

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[pkt1213]

It looks like the RS6 came with a 255/40R18, at least according to my google-fu. Would I be able to tell cluster that it was an RS6? I tried changing the cluster info in module 17 from 03283 to 03284. I found a VCDS page saying that xxx8x would be for 8 cyl and xxxx4 for turbocharged. However, looking at the VCDS page now looks like there is no 84 combo.

http://wiki.ross-tech.com/wiki/index..._(from_MY_2000)

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[rollerton]

Nah, that doesn't really do anything. In the C5 I don't think there are any adaptations/ software that will do what you want. It's in the EEPROM of the cluster.
Oddly enough you CAN do it in the same era VW's and A4's. B5/5.5 Passat and the B6 A4 have a 'distance multiplier' in the cluster that lets you correct for different wheel diameter.
Someone would have to modify the C5 cluster programming and invent or copy those tables . Not even sure that would work honestly..

[pkt1213]

I saw that. I could fix this by running a 35 series tire but I don't want to give up the sidewall. The roads around here are shit.

The Rosstech page lists +04 as Tires for Allroad. I tried 07283 but it wouldn't take it. In VCDS itself it doesn't say that is for tires though.

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[svt]

Did you ever solve this? I upgraded to 19" wheels with 255/35/19 tires and would try to correct the speedometer, if possible.