20 replies to this topic

[Angryelf]

I am looking to find out if GPS speedometer's are legal in the UK, i have looked online but there does not seem to be a definitive answer.

 

 

[DeadSquare]

I was told, 4/5 years ago, that at that date there was no specific rule,  but if a speedometer is fitted as part of the original equipment (tractors & Quad bikes for instance, weren't ), the speedometer or its replacement, had to be accurate at 30 MPH, or within 10% at other speeds.

 

As the radius of tyres is not a constant. a GPS is probably the most accurate speedometer available.

[phillrulz]

I was told, 4/5 years ago, that at that date there was no specific rule,  but if a speedometer is fitted as part of the original equipment (tractors & Quad bikes for instance, weren't ), the speedometer or its replacement, had to be accurate at 30 MPH, or within 10% at other speeds.

 

As the radius of tyres is not a constant. a GPS is probably the most accurate speedometer available.

 

Ive thought about this, but does GPS take into account gradients. Since driving up/down a hill would effectivly be a longer distance than driving in a flat plane as seen from above. Therefore a speed seen by an observer above would be slower than actuall speed at the tyres. 

[DeadSquare]

 

I was told, 4/5 years ago, that at that date there was no specific rule,  but if a speedometer is fitted as part of the original equipment (tractors & Quad bikes for instance, weren't ), the speedometer or its replacement, had to be accurate at 30 MPH, or within 10% at other speeds.

 

As the radius of tyres is not a constant. a GPS is probably the most accurate speedometer available.

 

Ive thought about this, but does GPS take into account gradients. Since driving up/down a hill would effectivly be a longer distance than driving in a flat plane as seen from above. Therefore a speed seen by an observer above would be slower than actuall speed at the tyres. 

 

 

That is why the Gps is always in touch with at least 3 satellites, because if there are 3 or more in contact, the altitude can be calculated, which means that the position of the speedometer is known in 3 dimensions.

[Shooter63]

Fist off I'm no expert in these things, but the only problem I can see is that a speedo has to run 10% fast for an IVA test so I presume all Speedos have to run fast, no doubt some techy will know how to do it.

Shooter

[Spider]

There are some dual driven speedos available that work on both GPS and also a take off from the vehicle. I think most of these default to the GPS, but if that's not available, say, around tall buildings, tunnels, trees etc, then if falls back on the vehicle take off.

 

I'd doubt they are legal for some of the reasons I've touched on, in that they can drop out and they can be slow to up date too in some conditions, ie, heavy cloud.

 

Also, I'm not up to speed with UK Laws, but as there's no Odometer, just on that basis alone, they are not legal here. Perhaps, if other wise legal, a separate Odometer can be fitted?

[Magneto]

I believe they do have odometers, I have a friend with one in his Moke, I'll ask him.....

 

Edit: My friend says his Smith's GPS speedo does in fact have an odometer.

Edited by Magneto, 24 August 2019 - 04:49 AM.

[DeadSquare]

I wish somebody made a 4"/100mm GPS speedometer to replace the Smiths and which match their rev counter;  the largest seems to be 80mm.

Edited by DeadSquare, 28 August 2019 - 06:23 AM.

[Magneto]

Did you check here?

 

https://www.digital-speedos.co.uk/

[Curley]

I'm 99.999% sure the last time I read the IVA/SVA test requirements the answer was no. You can get an adapter for the Speedo drive for a digital dash or add a wheel speed sensor at the rear.

[mini13]

Yep, essentially the speedo has to be working all the time, as it would with a cable, with the GPS ones, you can loose GPS lock, or it can take a time to get location on start up. Also there's the tunnel issue.

[DeadSquare]

As the engine is in the back of my Mini derivative, the speedo drive doesn't like negotiating two 180 degree bends.

 

I believe that Halda used to make a device, which somehow took the drive from the front wheel of a rear wheel drive, because this overcame the problem of wheel spin in slippery conditions.

[Spider]

As the engine is in the back of my Mini derivative, the speedo drive doesn't like negotiating two 180 degree bends.

 

I believe that Halda used to make a device, which somehow took the drive from the front wheel of a rear wheel drive, because this overcame the problem of wheel spin in slippery conditions.

 

Find an electronic one, that uses a Hall Effect pick up on the gearbox. They really super easy to install and wire up (even I can do it), easy to calibrate, (many have a self calibration facility now) and easy to re-calibrate with wheel and find drive changes too. Having run with a few of these now, I'd never go back to a Cable Driven Speedo.

[Richie83]

I wish somebody made a 4"/100mm GPS speedometer to replace the Smiths and match their rev counter; they're largest seems to be 80mm.

smiths do make one via Cai Gauges/GPS speedos. I’ve got one in my pickup.

[DeadSquare]

 

I wish somebody made a 4"/100mm GPS speedometer to replace the Smiths and match their rev counter; they're largest seems to be 80mm.

smiths do make one via Cai Gauges/GPS speedos. I’ve got one in my pickup.

 

 

Thank you.

 

I wonder why these haven't shown up in my searches.