125MPH on the clock

DavidMarsh

2019
CB650R ABS
Jul 29, 2021
Riding Since
1986
Since my first bike was nicked, I have no idea what the accurate GPS speed of the bike is... I had her up to 125MPH on Saturday what would that be in real terms
 

BIG6105

CBR650R ABS
Apr 19, 2022
Riding Since
1974
Never admit to breaking the law on a public forum m8 , you leave yourself wide open to …. Well you guess
 

Bran

2021
CBR650R ABS
Aug 31, 2022
uk
Riding Since
2010
type approval of vehicles means they have to be 10% accurate, my experience shows they tend to be 10% higher than the true speed, although there are points where this is more accurate. I've noticed 30mph and 50mph to be very close to the real speed. No idea why. This is the reason in the UK you usually get done recorded at 10%+1mph but anything less and you generally get away with it. from a legal point 1mph is sufficient to be charged but unlikely to be persued.
 

Tony650r

2020
CBR650R
Nov 30, 2021
Riding Since
2006
Since my first bike was nicked, I have no idea what the accurate GPS speed of the bike is... I had her up to 125MPH on Saturday what would that be in real terms
I too have also been at the track and reached 125mph or 200kmh very easily. Actually a little faster, around 220 and it had more to give. I had one of those gps speed apps running and it was dead on with the speedo up to maybe 120kmh. Above that looked no more than +- 5kmh. GPS speed really is that precise? Hell google maps often doesn’t know the difference if I’m on the highway or a service road right beside it.
 

tomonoak

CBR650R ABS
Sep 25, 2022
Riding Since
1972
GPS speed really is that precise? Hell google maps often doesn’t know the difference if I’m on the highway or a service road right beside it.
This is the difference between absolute GPS position and differential GPS position. Two readings taken close together in time may be a fair amount off in distance and direction, but since they're taken so close in time, they will be off by the same amount. So taking the difference between them, in order to calculate speed, cancels the inaccuracy.
 

Tony650r

2020
CBR650R
Nov 30, 2021
Riding Since
2006
This is the difference between absolute GPS position and differential GPS position. Two readings taken close together in time may be a fair amount off in distance and direction, but since they're taken so close in time, they will be off by the same amount. So taking the difference between them, in order to calculate speed, cancels the inaccuracy.
Ah yes that makes perfect sense. Thanks dude
 

Ian Warren

2021
CBR650R ABS
Mar 12, 2022
United Kingdom
Riding Since
2019
Never admit to breaking the law on a public forum m8 , you leave yourself wide open to …. Well you guess
I feel sure this was on a German Autobahn, in know mine was when I maxed the CBR650R (2021) was from memory the 148MPH was an actual 137MPH so the indicates speed was 8.03% higher than the indicated!
So 100 indicated would beb91.7 mph real!
Interestingly my Ducati Panigale V2 manual actually states the speedo under reads by 8%!
 

Ian Warren

2021
CBR650R ABS
Mar 12, 2022
United Kingdom
Riding Since
2019
type approval of vehicles means they have to be 10% accurate, my experience shows they tend to be 10% higher than the true speed, although there are points where this is more accurate. I've noticed 30mph and 50mph to be very close to the real speed. No idea why. This is the reason in the UK you usually get done recorded at 10%+1mph but anything less and you generally get away with it. from a legal point 1mph is sufficient to be charged but unlikely to be persued.
My CBR650R was 8.03 % higher indicated that actual and my Ducati panigale V2 manual states it’s 8%!
I think you will find the 10% figure is what level of accuracy is required in the construction and use regs which predate ABS and fairly accurate speed measurement (rubber wear will always affect this a little along with tyre pressure).
Also the 10% comes from speed cameras which are meant to trigger at speed limit + 10% + 2MPH.
 

Bran

2021
CBR650R ABS
Aug 31, 2022
uk
Riding Since
2010
As my note, "type approval" for motor vehicles sold in europe and posiibly elsewhere states the speedometer has to be within 10% accuracy. Doesn't state it has to be 10%. Type approval covers loads of things on motor vehicles not just speedometers
 
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