European speedos tend to read lower than US-built vehicles due to differences in regulation:
"European Union member states must also grant type approval to vehicles meeting similar EU standards. The ones covering speedometers   are similar to the UNECE regulation in that they specify that:
The indicated speed must never be less than the actual speed, i.e. it should not be possible to inadvertently speed because of an incorrect speedometer reading.
The indicated speed must not be more than 110 percent of the true speed plus 4 km/h at specified test speeds. For example, at 80 km/h, the indicated speed must be no more than 92 km/h."
Whereas in US
"Federal standards in the United States allow a maximum 5 mph error at a speed of 50 mph on speedometer readings for commercial vehicles."
(note: I didn't find the reg for noncommercial but rumour has it that it's similar)
So Euro speedos can be up to 10% fast but never under. US can be off by 5% under or over.
posted by 142.160....
Posts in this Thread:
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- Speedometer off based on GPS and ECU data, Brian, Fri, 17 Aug 2012 03:29:20
- Re: Speedometer off based on GPS and ECU data, Slug , Fri, 17 Aug 2012 04:42:44
- Same here, Vicsaero95, Fri, 17 Aug 2012 04:28:03
- Speedo error, Les_H, Fri, 17 Aug 2012 05:54:21
- Re: Speedo error, Dean, Fri, 17 Aug 2012 06:38:48
- Does that affect 0-60 tests etc.?, Tim, Fri, 17 Aug 2012 06:22:01
- Old tires read faster, shorter. nm, Norm95, Fri, 17 Aug 2012 06:21:59
- Mine reads 3mph fast, 03 Aero. NM, S-Works, Fri, 17 Aug 2012 05:34:00
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