How Good Is Your Speedo

[bigboy24]

ok i was wondering whats going on if im doing 30 by gps car reading 35mph and car reads 80mph gps is only reading 69

i know there not ment to be perfect but this is a bit ott what can i do any idea lads?

[chokit]

at 157, the my gps reads 154, only time ive really checked it. (obviously not on uk roads ) more likely you have a bit of a slow gps unit. which one do you have?

[P38Aaron]

i read my GPS speed, this has been covered a few times before.

my g/f's both GPS and Speedo are very close but my Lex different story...one of the reasons is wheel size of the wheels on your car that knocks the calibration of your speedo out.

manufacturers work in tolerances and speedo's should read close/under what your speed is

[Rory]

put slightly bigger tyres on

[atce4]

ok i was wondering whats going on if im doing 30 by gps car reading 35mph and car reads 80mph gps is only reading 69

i know there not ment to be perfect but this is a bit ott what can i do any idea lads?

I get similar results, 30 on gps is around 33 on the speedo and 70 on gps is 76 on speedo.

[spank-it]

Speedo - 100mph

GPS - 94mph

not to bad I thought.

FYI my car is standard on standard wheels

[Soon_2B_Lexus]

at 157, the my gps reads 154, only time ive really checked it. (obviously not on uk roads ) more likely you have a bit of a slow gps unit. which one do you have?

thats fast!

[Bazza]

at 157, the my gps reads 154, only time ive really checked it. (obviously not on uk roads ) more likely you have a bit of a slow gps unit. which one do you have?

thats fast!

and not in a IS300

[Bazza]

speedos are allowed to be out, i think its about 10% but they must over read, not under read

[Unforgiven]

Spot on, Con and Use regs allow for a 10% margin of error reading high. Think of it as a safety margin that could save you £60 and three points. Incidentally when I was a traffic cop nobody got done for less than 40mph in a 30mph limit because we exercised DISCRETION, we were not a bl**dy revenue making machine. Nowadays you hardly ever seen a traffic cop in London but plenty of yellow cameras, so much for road safety.