Speedo Reading?

[theblacktuscks]

I have successgully persuaded my good lady wife to allow me to prchase a Road Angel, Tom Tom software and a connecting cable to my XDA for my birthday!! I'm somewhat surprised that the Road Angel is indicating a lower MPH, at steady speed than my speedometer. Any other PH'er had similar result?

Regards,
Clive

[alans]

Yep, my RA reads about 8% lower than the speedo. On my last car (cerb) the speedo was spot on.

>> Edited by alans on Sunday 16th November 11:26

[grimbo]

At Bruntingthorpe last month the speedo showed about 15 to 20mph faster than the laser testing equipment.
That was when the needle stayed still long enough,once i go passed 120 it goes all over the place!!
The laser gear was set up on a long straight so the speeds were 157 by the laser so i guess at normal speeds the differance will be much less.

[jrb43]

Sorry to be boring but my father works in the motor industry (F*rd) and we've grown up knowing this. It is illegal for speedos to read less than the actual speed of the vehicle for safety reasons. Given that no speedo is 100% accurate and they are normally distributed around a mean error (I did apologise for being boring) manufacturers always set them to over read. That way, even if yours is one which "under reads" by the maximum error found in speedometers, it will still be legal ie. reading over your actual speed. For example, in the above mentioned manufacturer (I don't know about TVR), it's as much as 10%. There are ways of using this on the roads but I couldn't advocate it on this site.

[Mustang Baz]

Are people still finding Road Angels reading less than speedo? My speedo has started to give up the ghost this morning with Code L warnings and then mad variances, so I am relying on the Road Angel as a backup prior to repair/getting things sorted. RA generally always reads 3 mph less than digital/analogue speedo.

[powerlord]

my tomtom on my mobile is about the same.. 4mph or so under reading of speedo at 70.

so sounds like trevor speedo overreads by around 3% or so.

Since it's digital sender, I'd imagine all of em should be exactly the same amount of overreading.

[basil brush]

I guess it also depends on what profile rear tyres you have, as i assume tvr fit the same sensor to both S and std models. Mine is around 10% out.

[DrDaveWatford]

This is I'm told standard across the board - speedos generally overestimate the speed. This may be a deliberate attempt to keep us within the speed limits rather than a technical issue....... My M3 speedo always shows a few MPH more than my Road Angel, and I hear that this is the case with other cars too.

[bogie]

yep - all completely normal as designed...all speedos read over by a certain degree.

Ever looked in the test results in Autocar where theres the table of speedo reading vs true speed?

[M-G]

Having used my Road Angel in the Tuscan, Freelander and my trusty MG BGT I have found the Freelander is 10% out, the Tuscan is slightly better at 5-8% and the BGT is 1 mph out all the way round the speedo! Says a lot for cable drive.

Mark

[scott672003]

all car speedos' electronic or cable are deisgned with minus zero perscent tolerance,, and hence all have a plus reading,,,,,, your road angel will be more accurate probably plus or minus 1%...

I have tom tom and it reads about 5mph less than all my cars,,, apart from the old triump gt6,,, which is extremely optimistic,, and reads about 10mph faster than it actualy is traveling.
cheers
scott...