Hi i have changed my tyres from 55 profile down to 50 profile, will my speedo be out??? also i have a teg box does this effect speedo as my ratios are different???

i just dont know where the car measures travelling speed from, engine, wheels gearbox??????

 

50 is the stock size
so it should read correctly on the cluster

 

nah man 55 is the stock...in the UK anyway... that is correct for sure.