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Can i legally use a sta nav as my speedo ?
steve m - 25/2/12 at 04:40 PM

my speedo, has always been eratic , and now doesnt work at all,
so can i legally use my tom tom as the speedo ?

also what about the mot ?

regards

steve

[Edited on 25/2/12 by steve m]

sdh2903 - 25/2/12 at 04:52 PM

Its law to have a functioning Speedo but not sure what form it can take. Its not checked as part of the MOT.

loggyboy - 25/2/12 at 04:57 PM

quote:
Originally posted by sdh2903
Its law to have a functioning Speedo but not sure what form it can take. Its not checked as part of the MOT.


It is in the MoT now (as of Jan 12), and as most MoT stations are in doors, and GPS tends to only work outdoors, and only when your moving! I would assume it would fail. The argument would be that in a tunnel or very built up areas your speedo would not function.

If your speedo is erratic its probably just the cable.

[Edited on 25/2/12 by loggyboy]

gunman - 25/2/12 at 04:58 PM

I'd imagine not as it's not 100% dependable. What happens in a long tunnel for instance?

plentywahalla - 25/2/12 at 05:10 PM

Interesting reading here

http://support.runkeeper.com/discussions/problems/1630-what-is-the-gps-sampling-frequency

I think the answer would be no.

russbost - 25/2/12 at 05:37 PM

I sell gps speedos as secondary speedos for driving school cars & the like, they are fine as a secondary speedo, but cannot legally be your only form of speedo.

deltron63 - 25/2/12 at 06:44 PM

No

Neville Jones - 25/2/12 at 07:43 PM

I'm using a £7.99 pushbike speedo from Halfords in my old Transit.

Been to Scotland and back a couple of times and still performing flawlessly.

Only downside is that the odometer stops at 1023miles.

Cheers,
Nev.

paulf - 25/2/12 at 10:36 PM

I have used a bike speedo for years on my locost in addition to the dash speedo, it serves as a clock and trip distance as well as giving average and maximum speed read outs.Alot of newer versions are wireless but would not be very good on a car the cheaper ones with a cable would be fine though.
Paul

quote:
Originally posted by Neville Jones
I'm using a £7.99 pushbike speedo from Halfords in my old Transit.

Been to Scotland and back a couple of times and still performing flawlessly.

Only downside is that the odometer stops at 1023miles.

Cheers,
Nev.

rusty nuts - 26/2/12 at 09:21 AM

quote:
Originally posted by loggyboy
quote:
Originally posted by sdh2903
Its law to have a functioning Speedo but not sure what form it can take. Its not checked as part of the MOT.


It is in the MoT now (as of Jan 12), and as most MoT stations are in doors, and GPS tends to only work outdoors, and only when your moving! I would assume it would fail. The argument would be that in a tunnel or very built up areas your speedo would not function.

If your speedo is erratic its probably just the cable.

[Edited on 25/2/12 by loggyboy]


Not quite right, the speedo has to be present but there is no check on it's operation!

It might be better to get the original speedo sorted out? Had a Mini speedo recalibrated and serviced by Speedy Cables a few years ago , they may be able to help?

TheGiantTribble - 26/2/12 at 12:47 PM

don't know if they are legal or not but...

A couple of months ago I was intrigued by the apparent inacreate-ness-nous (is that a word?) of the speed that the sat nav said I was doing.

So I experimented, going along leval roads at a consistant speed (70MPH) the sat nav would be showing approx 68MPH
However when going uphill or down, Car still going at 70Mph the Sat Nav would read approx 65MPH

It would apear (at least in theory) that the Sat Nav's don't allow for the curve of the earth, or at least not over a realtively short distance.

Anyway just my observations, and theory please regarding the inacr..inacreatno...how wrong Sat Navs can be.
Feel free to shout me down, blast me out the water, or prove me wrong

Slimy38 - 27/2/12 at 05:38 PM

Along the same lines, would an Android tablet running the Torque application serve as a valid speedo, along with all the other options that it gives?

I was just wondering whether a cheapo tablet mounted in the dash and connected to the engine management port would be a viable option.

russbost - 27/2/12 at 07:55 PM

quote:
Originally posted by Slimy38
Along the same lines, would an Android tablet running the Torque application serve as a valid speedo, along with all the other options that it gives?

I was just wondering whether a cheapo tablet mounted in the dash and connected to the engine management port would be a viable option.


No, no gps speedo is road legalas far as main speedo is concerned TTBOMK

Peteff - 27/2/12 at 08:11 PM

quote:
Originally posted by TheGiantTribble
don't know if they are legal or not but...

A couple of months ago I was intrigued by the apparent inacreate-ness-nous (is that a word?) of the speed that the sat nav said I was doing.


I think the word is innacuracy In the van with cruise set at 70 it reads 67 and is probably more accurate than the speedo on a long straight motorway section but as you say on long hills or bends it does go a bit out.

JF - 28/2/12 at 01:20 AM

quote:
Originally posted by TheGiantTribble
don't know if they are legal or not but...

A couple of months ago I was intrigued by the apparent inacreate-ness-nous (is that a word?) of the speed that the sat nav said I was doing.

So I experimented, going along leval roads at a consistant speed (70MPH) the sat nav would be showing approx 68MPH
However when going uphill or down, Car still going at 70Mph the Sat Nav would read approx 65MPH

It would apear (at least in theory) that the Sat Nav's don't allow for the curve of the earth, or at least not over a realtively short distance.

Anyway just my observations, and theory please regarding the inacr..inacreatno...how wrong Sat Navs can be.
Feel free to shout me down, blast me out the water, or prove me wrong


On a flat straight road a satnav will usually be more accurate then your normal speedo. It is nearly impossible to get a traditional speedo 100% accurate. If only for the dependency of the wheels turning the speedo, or its sender if electronic. Even the wear of your tires will change it's accuracy slightly. Not to mention mounting tires of a slightly different size (same spec different model will differ!).

As in most countries a speedo is allowed to indicate a slightly higher speed then actually driven, but not lower, manufactures usually make sure the speedo is a few km/h out.

Satnav does not depend on the wheels and is therefor free from that factor, and will therefor be more accurate on a level straight road. The problem is however that most satnavs don't account for altitude at all, and those that do are not always as accurate in height as they are in the horizontal plane. Effectively it's measuring your speed across the map, not across the actual land.

So your standard speedo isn't accurate. But it has the same deviation on a level road and a steep incline, seems to be about 2MPH at 70 in your case. The satnav is normally quite accurate, but start to deviate more and more when the road gets steeper. And different satnavs might give different readings on that very same hill.

Slimy38 - 28/2/12 at 06:27 AM

quote:
Originally posted by russbost
quote:
Originally posted by Slimy38
Along the same lines, would an Android tablet running the Torque application serve as a valid speedo, along with all the other options that it gives?

I was just wondering whether a cheapo tablet mounted in the dash and connected to the engine management port would be a viable option.


No, no gps speedo is road legalas far as main speedo is concerned TTBOMK


Sorry, the Torque app isn't a GPS application, it uses OBDII engine management to report on things. So obviously the restriction would be a modern engine with a compatible ECU, but it's all contained within the car it doesn't need anything externally.

russbost - 28/2/12 at 08:56 AM

"Sorry, the Torque app isn't a GPS application, it uses OBDII engine management to report on things. So obviously the restriction would be a modern engine with a compatible ECU, but it's all contained within the car it doesn't need anything externally."

Sorry, my misunderstanding completely. If it's connected to the OBD info, then I would assume it's getting it's speed info from the OE sensor, just as the standard speedo would, in which case can't see any reason why that wouldn't be legal (tho' may not be ok for IVA as you may not be able to get info to prove it's capable of displaying max design speed etc.).The only argument I can see would be that it could be regarded as a "temporary fitment" -no idea what the takeof Mr Plod, or VOSA for that matter, would be on that

Slimy38 - 28/2/12 at 09:41 AM

Thanks for the info, sounds like too much of a grey area to try and risk it!