speedo or road angel?

[carlb]

just got a road angel, now the gps speed on the road angel is less than that on the speedo

which one would you trust?

for example, at 70 on the speedo the road angel shows 64 and then when the speedo shows 80 the road angel shows 70

which one is most likely to be most accurate

i would have said the road angel but the difference seems too much, when i'm in traffic at 80 in the cerb it would appear to be correct based on the number of people that i over-take and those that over-take me.

what do you think...

[tvr5000]

The Road Angel. All the cars I have driven with the Road Angel have shown a difference of 5mph when doing 70mph. The speedo has always been higher. from tvrs to the latest rep mobiles, they all show the same difference.

[petclub]

Speedos are not known to be accurate and it's in manufacturer's interest for them to read slightly higher than 'true'.

[ntel]

My Tuscan 2 seems to display a low figure. When Traveling at 70mph on the speedo, the RA or Tom Tom reads 73mph. The difference gets larger the faster I go, so I always ignore the speedo.

[RUSSELLM]

I've always been under the impression, that all car speedo's over read.

I'd side with the road angel.

In fact, when it comes to the Tiv, I'd trust a five year old's opinion over anything the car displays.

[Mats]

One thing I would add is Rolling Resistance. The Cars Tyres have an effect on the cars speed. I used to have 30 profiles on my Tuscan but changed to 40 profiles as they handled better. The speedo reading changed by 5MPH (approx) I always go with the Road Angel FWIW.

Cheers.

[pdV6]

Speedos are not allowed to under-read at all. Therefore any manufacturing & calibration tolerances err on the high side.

At a steady cruise in a straight line, your RA will be very accurate indeed. Less accurate during rapid changes in speed and direction, though.

[aaandy]

Road Angel every time, should be more accurate. In fact the handbook even boasts about how they are extremely accurate. When driving I nearly always now refer to the road angel for speed instead the speedo.

[Touching Cloth]

Strangely, at any speed above 50mph, the Speedo on my Cerb is bang on accurate against my Garmin Nav unit; 70 is dead 70, 90 dead on 90 tested upto 140ish (private road yadda yadda yadda). Unfortunately speedo doesn't start moving at all until about 30 and then misreads all over the place until I hit 50.

Odd

[gazzab]

surely a RA will not be accurate on a hill - ie am not sure it copes with hills?

[pdV6]

gazzab said:

surely a RA will not be accurate on a hill - ie am not sure it copes with hills?

Think it would have to be a flipping long and steep hill to throw it off too far in the normal course of events.

[shorts!]

Road angel is to be trusted over speedo everytime unless accelerating or decelerating hard. In the t350 below 70 the speedo is about 2 or 3 mph above RA. At higher speeds; (obviously not on the public highway etc, etc) they both read the same at about 90, and 120 but above this I really couldn't tell you.
When I had the use of a Boxster for a couple of weeks the speedo was consistently 7 or 8% higher than the RA. You could say this is quite a safe way of doing things as in a 40mph limit, at an indicated 40mph, you'd be travelling at 37 for instance. The cynic in me though might say at high speeds the Boxster driver might be under the impression that their car is appreciably faster than it is. Might have just been the one I was in of course.
On the hard acceleration/ deceleration issue the car speedo isn't a second behind as the RA often appears to be so one could have some chilidish amusement trying to get a silly difference between the 2 . . . .

[chris watton]

RA, every time, except yesterday, on my way back from work in the Tam, when it seemingly got so hot that the magnetic ring holding the unit in place in the bracket, on the windscreen decided to melt, and the unit ended up in my drivers footwell - bloody bumpy country lanes! lol

[Tripps]

pdV6 said:

gazzab said:

surely a RA will not be accurate on a hill - ie am not sure it copes with hills?

Think it would have to be a flipping long and steep hill to throw it off too far in the normal course of events.

The calculations are based on 3D positions, so it should be taking the entire distance travelled between the last fix into account, unless the software used is being lazy.

[carlb]

chris watton said:

RA, every time, except yesterday, on my way back from work in the Tam, when it seemingly got so hot that the magnetic ring holding the unit in place in the bracket, on the windscreen decided to melt, and the unit ended up in my drivers footwell - bloody bumpy country lanes! lol

yea, mine melted as well, clearly it was designed for a pre global warmed uk climate...