MGB GT speedo issues

[MGsimon]

Hello all, iv just brought myself a well looked after 78 gt in vermillion red.



I was taking her over to the paint shop last night to get a few small surface rust and paint bubbles sorted before the winter comes in a I noticed on my sat nav that the speedo is reading rather high.

When doing 30 it says 40 and when doing approx 75 it reads 90ish.

HELP

[MGsimon]

williredale said:

Could be the wrong speedo fitted. What does it say on its face?
Or it could be wrong sized tyres. What do the sidewalks say?
Or something else! But those two are easy to check.

Also, is the odometer reading correctly?

The car is in the paint shop ATM so can't check those things I did notice to the car doing a mile the sat nav said 0.8 of a mile.

[MGsimon]

She is in for some welding work and rust being sorted around the windows, which I feel making her water tight is a concern. She drives and runs fine the speedo issue is the only problem iv come over so far ( famous last words )

[MGsimon]

Iv driven others and other people who have owned Bs in the past have even said mine drives better.

But this is my only car so it won't be getting put away for the winter etc just dealing with the rust and sealing underneath so no more welding will be needed in the near future.

Only asking what could be causing the issue with my speedo

[MGsimon]

Thanks guys. I will be doing this as soon as it's back. Also iv found out she now needs some new fuel lines.

Here is the rust that has been sorted.

[MGsimon]

Expatloon said:

MGsimon said:

a few small surface rust and paint bubbles sorted before the winter comes in

In hindsight something of an understatement !

Where is that bottom right a photo of ?

Yea was bit of a understatement glad I got it checked out. The bottom right picture was of under the rear bumper where it attaches to the car. Was rotted though both bits of metal, lucky it didn't get on to the chassis

[MGsimon]

Hi all, I now have my car back and first thing I did was to check the tyre sizes. They are 185/70R 14!

Would this course of my issue ?

[MGsimon]

I'm reading approx 30 when doing 20 if that helps.