Bike speedometer - accurate?
Discussion
I rode past one of those “Your Speed” illuminated signs and when it said 30 mph my speedo was showing less than 30 (i.e. it is under-reading).
[The bike is a 2001 Yamaha XJ600 with the standard front tyre size]
My car reads 32/33 mph when the same sign shows 30.
I thought speedometers must never under-read (EU regulations) and I don’t have anything to compare the speed against GPS.
Surely the bike can’t be right?
Or is the speed sign getting it wrong?
[The bike is a 2001 Yamaha XJ600 with the standard front tyre size]
My car reads 32/33 mph when the same sign shows 30.
I thought speedometers must never under-read (EU regulations) and I don’t have anything to compare the speed against GPS.
Surely the bike can’t be right?
Or is the speed sign getting it wrong?
Plinth said:
I rode past one of those “Your Speed” illuminated signs and when it said 30 mph my speedo was showing less than 30 (i.e. it is under-reading).
[The bike is a 2001 Yamaha XJ600 with the standard front tyre size]
My car reads 32/33 mph when the same sign shows 30.
I thought speedometers must never under-read (EU regulations) and I don’t have anything to compare the speed against GPS.
Surely the bike can’t be right?
Or is the speed sign getting it wrong?
I've got one of these near my house, it flashes 30mph no matter what speed I'm doing. I've driven past at 15/20 before and it flashes up.[The bike is a 2001 Yamaha XJ600 with the standard front tyre size]
My car reads 32/33 mph when the same sign shows 30.
I thought speedometers must never under-read (EU regulations) and I don’t have anything to compare the speed against GPS.
Surely the bike can’t be right?
Or is the speed sign getting it wrong?
Could just be an anomaly, sometimes there is a lag in your speedo or their indication.
Last week I went through one in a 40mph limit thought I was doing about 40mph, it flashed up 35mph "thankyou" and I glanced down and saw near 50mph on my speedo....WTF my speedo is well out ? so I went back through the same one later that day in the opposite direction and made an effort to be bang on 40mph on the speedo, just to check and "38 mph thankyou"
I wouldnt worry about it too much. Generally I find speedos on my cars/bikes 1-3 mph high at 30mph and 40mph, but sometimes 10mph high by the time you are in 3 figures.
Last week I went through one in a 40mph limit thought I was doing about 40mph, it flashed up 35mph "thankyou" and I glanced down and saw near 50mph on my speedo....WTF my speedo is well out ? so I went back through the same one later that day in the opposite direction and made an effort to be bang on 40mph on the speedo, just to check and "38 mph thankyou"
I wouldnt worry about it too much. Generally I find speedos on my cars/bikes 1-3 mph high at 30mph and 40mph, but sometimes 10mph high by the time you are in 3 figures.
Thanks for the replies.
It seems those signs are a bit random, then.
I was hoping that I could use it to check my bike, because….
…my speedometer was showing 35 when I went past a camera van the day before.
If it is under-reading there will be a NIP in the post.
If it is working correctly (i.e. exaggerating the speed slightly, as the regulations says it should do) I will be OK.
It seems those signs are a bit random, then.
I was hoping that I could use it to check my bike, because….
…my speedometer was showing 35 when I went past a camera van the day before.
If it is under-reading there will be a NIP in the post.
If it is working correctly (i.e. exaggerating the speed slightly, as the regulations says it should do) I will be OK.
I'm not sure if the same legislation applies to bikes as cars (although I can't think why it wouldn't) but they have inaccuracies of less than <10%.
With the change of rolling diameter due to tyre wear, snow tyres, pressures, or even (in the case of cars) different wheels, manufacturers will tend to get the over-read on the upper end of what is permitted, as it reduces the risk of litigation.
Back to GPS confirmed speeds. These are more accurate than your speedo, but not supremely accurate, and not at higher speeds. You often get people on car/bike forums saying that the "over read on their car dissapears above 80mph etc.", the reality is that its far more likely that their mobile phone GPS has reached the limits of it's accuracy, and is simply as inaccurate as their car speedo, the speeds therefore look the same.
That's why calibrated and specialist equipment is used for racing/timing purposes, and why the police in England and Wales give you 10% +2mph on top of limits at their discretion (Scotch Police refuse to divulge the exact figures but it's widely believed to be the same). So in a 30mph limit, you could potentially have an indicated 38mph before you reach the threshold for a FPN... Which is often why I personally have little sympathy for those busted in built up areas.
With the change of rolling diameter due to tyre wear, snow tyres, pressures, or even (in the case of cars) different wheels, manufacturers will tend to get the over-read on the upper end of what is permitted, as it reduces the risk of litigation.
Back to GPS confirmed speeds. These are more accurate than your speedo, but not supremely accurate, and not at higher speeds. You often get people on car/bike forums saying that the "over read on their car dissapears above 80mph etc.", the reality is that its far more likely that their mobile phone GPS has reached the limits of it's accuracy, and is simply as inaccurate as their car speedo, the speeds therefore look the same.
That's why calibrated and specialist equipment is used for racing/timing purposes, and why the police in England and Wales give you 10% +2mph on top of limits at their discretion (Scotch Police refuse to divulge the exact figures but it's widely believed to be the same). So in a 30mph limit, you could potentially have an indicated 38mph before you reach the threshold for a FPN... Which is often why I personally have little sympathy for those busted in built up areas.
Jokes aside as already said I've never seen underread but all my bikes overread
I can only compare to GPS (Google/Waze etc) But my MV 800 was genuinely the closest and at 71 GPS would read 70
My 16 Tuono was about 1-2 mph depending on speed
My 19 Tuono with the updated TFT dash is 2-3mph depending on speed
My 18 GSXR1000 just makes it up. It must be 7-8mph out when you get 100+mph on track
I can only compare to GPS (Google/Waze etc) But my MV 800 was genuinely the closest and at 71 GPS would read 70
My 16 Tuono was about 1-2 mph depending on speed
My 19 Tuono with the updated TFT dash is 2-3mph depending on speed
My 18 GSXR1000 just makes it up. It must be 7-8mph out when you get 100+mph on track
Step 1 - download free GPS speedometer app on phone.
Step 2 - duct tape phone to tank avoiding tape on screen
Step 3 - go for a ride and compare against speedometer
Step 4 - report back how accurate your speedometer is.
On my case the ‘new’ bike overreads by a couple of mph. The ‘old’ bike under reads. U up to 10mph...but then again I doubt there were too many speed cameras in 1947. But always good to know what the speedometer has to read for any actual speed.
Step 2 - duct tape phone to tank avoiding tape on screen
Step 3 - go for a ride and compare against speedometer
Step 4 - report back how accurate your speedometer is.
On my case the ‘new’ bike overreads by a couple of mph. The ‘old’ bike under reads. U up to 10mph...but then again I doubt there were too many speed cameras in 1947. But always good to know what the speedometer has to read for any actual speed.
In my case:
Step 0 – buy a phone (I don’t have one…)
Step 1 - download free GPS speedometer app on phone.
Step 2 - …………
The bike is 100% standard – I have read online that older Yamaha speedometers tend to exaggerate the speed (hopefully….)
Interesting to read how accurate the more modern bikes are – my T-reg 1200 Bandit was a bit of a liar! (or ego-booster).
Yep, totally down to me if I get a NIP (lapse in concentration – had been trundling along slowly until almost the end of the village, opened the throttle a bit too early….then the van came into view…he was about 70 yards into the 60 limit, looking to catch people like me accelerating before the NSL signs.)
We are “allowed” 10% + 2 mph here, so if my speedo showed 35 and I don’t get a ticket, it is either accurate or slightly over-reading. If I get a NIP (first one ever), it’s under-reading.
Step 0 – buy a phone (I don’t have one…)
Step 1 - download free GPS speedometer app on phone.
Step 2 - …………
The bike is 100% standard – I have read online that older Yamaha speedometers tend to exaggerate the speed (hopefully….)
Interesting to read how accurate the more modern bikes are – my T-reg 1200 Bandit was a bit of a liar! (or ego-booster).
Yep, totally down to me if I get a NIP (lapse in concentration – had been trundling along slowly until almost the end of the village, opened the throttle a bit too early….then the van came into view…he was about 70 yards into the 60 limit, looking to catch people like me accelerating before the NSL signs.)
We are “allowed” 10% + 2 mph here, so if my speedo showed 35 and I don’t get a ticket, it is either accurate or slightly over-reading. If I get a NIP (first one ever), it’s under-reading.
Plinth said:
We are “allowed” 10% + 2 mph here, so if my speedo showed 35 and I don’t get a ticket, it is either accurate or slightly over-reading. If I get a NIP (first one ever), it’s under-reading.
Not sure on that, I got a ticket for 79mph in a 70mph which would suggest that is when they start issuing tickets.dc2rr07 said:
Plinth said:
We are “allowed” 10% + 2 mph here, so if my speedo showed 35 and I don’t get a ticket, it is either accurate or slightly over-reading. If I get a NIP (first one ever), it’s under-reading.
Not sure on that, I got a ticket for 79mph in a 70mph which would suggest that is when they start issuing tickets.Plinth said:
dc2rr07 said:
Plinth said:
We are “allowed” 10% + 2 mph here, so if my speedo showed 35 and I don’t get a ticket, it is either accurate or slightly over-reading. If I get a NIP (first one ever), it’s under-reading.
Not sure on that, I got a ticket for 79mph in a 70mph which would suggest that is when they start issuing tickets.kiethton said:
bogie said:
Generally I find speedos on my cars/bikes 1-3 mph high at 30mph and 40mph, but sometimes 10mph high by the time you are in 3 figures.
My exige goes the other way - speedo says 30, i'm doing 28.....speedo says 110, I'm doing 113.....(both versus Waze GPS)https://www.unece.org/fileadmin/DAM/trans/main/wp2...
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