INACCURATE SPEEDOMETER

[mrick]

I have just had to attend a Speed Awareness Course for travelling at 24 mph in a 20 mph Restricted Area (in London)...
Most L/w owners will be aware that, quite apart from the speedo not being particularly accurate, the speedo needle tends to "wave around" a bit!
I don't want to be "done" again - next time, it would be a £100 Fine + Points - so need to have an accurate indication of the vehicle's speed.
The Trainer on the Speed Awareness Course suggested fitting a Satnav - it would need to be an HGV model, as my LR is 24 volt FFR. "Honest John" has suggested an "App".
I don't have a Smartphone, so I would be grateful for Members' views. Essentially, what I need is a very accurate Speed Indicator which is as easy to read as possible (and will operate from the 24 v Auxiliary Power Socket).

[fv1620]

I think these days most satnavs are 12v/24v I have run Tomtom & Garmin off 24v.

Think you need to avoid fiddling with a phone as that might invite further scrutiny with it running on the dash?

[stanfonj]

I use one of these:
https://www.ebay.co.uk/itm/304530507967 ... media=COPY

It’s cheap and works great. Nice clear display and I have it mounted on the steering column shroud. Easy enough to remove if you want to hide it.

[jor henderson]

Do you have long wheelbase rims fitted?

[mrick]

Thank you for the suggestions so far.
"No" to LWB Q.
GPS Speedo looks to be the best option so far, but how to connect to a 24v system (Ididn't realise 24 volt would produce so many problems!)?

[jor henderson]

Why I asked was, if your speedo overreads now, why not try a long wheelbase one, it should read closer.

[TeZZ]

I use one of these:
https://www.ebay.co.uk/itm/304530507967 ... media=COPY

It’s cheap and works great. Nice clear display and I have it mounted on the steering column shroud. Easy enough to remove if you want to hide it.

I have a similar on fitted to mine, I have a cigaret lighter jack and a converter plug installed to power it via a usb plug, something like this;

https://www.ebay.com.au/itm/36344534710 ... 0af265a603