Tyre load rating dvice for those gone from 19 to 20

[RIV]

I used to run 275.30.19 on my b7 I also had a rd pilot fitted to the car, I can tell you for a fact it will put your speedo out

[nij]

haha when I pass those signs at 30mph it says 30mph???? sure your alloys aren't square fella

The council must have set the one you've driven pass to over read.
I've just put my set of nearly new 255/35/19 winter tyres back on and the RNS-E Sat Nav is showing 26mph when I have the cruise control set at 30mph, where as it would show about 29mph with my 265/30/20 setup.

The UK speedometer law is based on the EU standard, with some minor changes. A speedo must never show less than the actual speed, and must never show more than 110% of actual speed + 6.25mph. So if your true speed is 40mph, your speedo could legally be reading up to 50.25mph but never less than 40mph. Or to put it another way, if your speedo is reading 50mph, you won’t be doing more than 50mph but it’s possible you might actually only be travelling at 40mph.

To ensure that they comply with the law and make sure that their speedometers are never showing less than true speed under any foreseeable circumstances, car manufacturers will normally deliberately calibrate their speedos to read ‘high’ by a certain amount.

[geordie jay]

so when the law stops me and says im doing 35 in a 30 I explain that its the manufacturers fault then??

[nij]

No, it's the other way round. If your speedo is reading 30mph then you are doing 30pmh or less.

[geordie jay]

pmsl mate you got my brain mashed

[RIV]

pmsl mate you got my brain mashed

Rolling radius