Quick tyre size question

[Trubble]

for a 10 year old car the speedo aint gonna be right after 20mph... i mean when im doing 80mph on the clock im doing 70mph on the sat nav

 

[sprint]

100mph on the speedo in mine is 93 according to sat nav, so 7% out at 100 but i did notice it varies alot depending on what speed your doing, around 50 was pretty much spot on iirc, but above and below that there was a noticeable difference.

nice car danshieber, you have already moved on and i nearly am so the twins are being sold on