Speedometer question

[Neil Sheath]

My speedo under reads by about 3 to 4 mph. For example when it is indicating 56mph I am actually travelling at 60mph. I have verified this with speed awareness signs and several different gps units. They all provide consistent and similar results.

My question is, is it possible to adjust the speedometer in any way to make it read more accurately?
Thank you

[Lingen]

Neil.
It can be done reasonably easily if you feel able to get inside it. Basically it is a case of carefully rotating the alloy disc inside by hand till the needle reads 56 mph. Hold it in that position, and ease the needle off its shaft, and replace it in the 60mph position. It still might not be entirely accurate at 30 or 70 mph though, but should be nearer the mark.
Mike.

[Neil Sheath]

Thank you Mike. Car is in having the heads done at the moment then is away to get a new hood so I will do it when I get the beastie back.

[richardthestag]

I have had a very good service from speedy cables https://www.speedycables.com/

on a couple of speedo heads that needed recalibration.

bear in mind tyre size, gearbox and diff will have an impact on what the speedo is saying.

[trunt]

If it’s reading low at all speeds then slipping the needle as Mike suggests is going to be fine, if not it can still be a good cheap compromise!

[Wheelz]

You didnt say that you ruled out other causes, namely

1. That the diff is not the correct ratio?
2. The tyre sizes?
3. An incorrect type speedometer is fitted (Tr saloons have different revs/mile)?