speedo wrong?

[chris477]

Hi all.

Iv got a 3 door corsa ls 1994.
Cable driven speedo

The speedo shows the wong speed.

Say its saying im doing 30 but im only really doing 25ish.

Iv tested this by 2 phones with gps speedo apps.

Any fix i could do?

Thanks

[diggerhole]

Gas speedo apps have lag. They always read under. Can you confirm current tyre size and model of car.