By law a speedo can't under read, but the tolerance for over reading is quite high, so it's far safer for the manufacturers to verge on the side of caution, although Ford do seem to take it a bit further than most.
From old to new tyre on mine using the sat nav as a baseline, I got 2mph variance at 70mph. Each mm of tread gives a greater % of circumferance change on a smaller wheel.
Bob
Accompanied by the sound of a chisel on slate moray, managed to produce the following words of wisdom
My Scorpio, according to sat-nav is very close to being accurate. 70mph on the sat-nav is 71 on the speedo.
My Golf, at 70 on the sat-nav is reading 76 on the speedo
The Range Rover at sat-nav 70 indicates 72 - but it's got oversize tyres (235s instead of 205)
On Thu, 20 Sep 2007 10:14:34 +0100, John Frum wrote (in message ):
I just thought I'd better add that car 1 is a 130 rather than 115.
Well I have 130 tdci and get between 27-32 mpg while towing a 17 ft van never have i had 42 while towing
Solo I get around 47mpg I think your mate is telling a few porkies!!!!
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