View Full Version : Speedo not running true...
crashe
1st May 2005, 18:09
I have just been told that my speedo must be out.
When coming back from Hamilton yesterday, both Feint and Limmy have just said that I was going well over the speed limit... yet my speedo said I was doing 120km.
Yes I know, that is well over the speed limit but they say I was doing 140 +
Now I am really shocked at this.... as I do normally stay at around 100 to 110km on the motorway.
So where would one go to get the speedo checked and what would it cost to do this...
Do speedo's go out of sync like this often??????
I am not in any great hurry to get it done.... as the bike will be in the gargage for 2 months on Thursday night. But to get this info now will be of great help for when I am back up and riding again.
Thanks in advance.
Jeremy
1st May 2005, 20:04
It looks like you've managed to get a speedo that might actually be showing the real speed. Most bike speedos are out by about 5 - 10km/h at 50km/h. It can get worse the faster you go. Mainly it's done by the manufacturers so you don't break the speed limit.
jazbug5
1st May 2005, 20:27
Wrong way round, I think.
pyrocam
1st May 2005, 20:28
Try going to one of the AA service centres or VTNZ places with those rolling wheels in the ground that you stick the back wheel on. Ive been tempted to do it myself but havent had time yet.
If you approach the right person and be really nice to them they might do it for free. Im talking about the guys on the floor not the office workers. it would only take a second.
I thought my bike's speedo was overestimating untill I got pulled over at 88 and it felt like I was doing mybe 75. wasnt checking it :(
I have just been told that my speedo must be out.
When coming back from Hamilton yesterday, both Feint and Limmy have just said that I was going well over the speed limit... yet my speedo said I was doing 120km.
Yes I know, that is well over the speed limit but they say I was doing 140 +I think the boys (Feint & Limmy) must have eaten too much Burger King??
1. If you rarely exceed the speed limit I'd find it hard to believe that you were doing 140kmph without noticing!
2. I know that speedos are calibrated to show a 'faster' speed than the actual, but I've never heard of one showing 20kmph slower...if the boys are correct then there may be a fault and you will need to have the speedo recalibrated or repaired/replaced professionally.
2 months is a long break from two wheels, I hope you make it through with few side effects! :ride:
Try going to one of the AA service centres or VTNZ places with those rolling wheels in the ground that you stick the back wheel on. Ive been tempted to do it myself but havent had time yet.I think you'll find that those "rolling wheels in the ground" are for testing brakes not speedometer calibration! Might work on the Virago though? :laugh:
crashe
1st May 2005, 20:42
I think you'll find that those "rolling wheels in the ground" are for testing brakes not speedometer calibration! Might work on the Virago though? :laugh:
AHEM, you cheeky buggar... lol.
YES! crashe.. the 1st KB ride I went on (noob ride to wellsford) you stuck at 140 the whole time!... I think you are right about it being out.
bugjuice
2nd May 2005, 09:29
when you stick a vehicle on a dyno, doesn't that show true speed? There's a few places around that dyno bikes, may be give them a call and find out.
I'm interested in getting mine done too, so if/when you do find out, let us know ;)
F5 Dave
2nd May 2005, 10:14
when you stick a vehicle on a dyno, doesn't that show true speed? There's a few places around that dyno bikes, may be give them a call and find out.
I'm interested in getting mine done too, so if/when you do find out, let us know ;)
Yeah the dyno should show the true speed (if it is a decent one) But this will only work on the back wheel. Older bikes have the gear drive for the speedo on the front. Only recent bikes with electronic pickup this will work on. Changing tyres or gearing will mess this up too.
A speedo healer will allow you to adjust this error on electronic units. Costs ~ $130Aus. Dunno if avail in NZ, Google one up.
Old world instrument technicians can fix mechanical instruments. Good luck finding one.
Jantar
2nd May 2005, 10:16
Fit a hand held GPS unit to your handle bars (cable ties will hold it in place) and just ride. You'll soon see how your speedo compares to true speed.
pyrocam
2nd May 2005, 10:42
I think you'll find that those "rolling wheels in the ground" are for testing brakes not speedometer calibration! Might work on the Virago though? :laugh:
yes I know they are, but I think they have a speedometer to measure how fast your going next to it. didnt get a close look but it appeared to be one.
*edit. now that I think about it. Im proberly wrong. Ive only seen one once at the Kingsland one. It looks like one but could be anthing with a gauge on it I suppose
the GPS is a good idea but expensive if you dont know someone with one. Originally I was going to get someone with a car to race me along the straight on the 22 with my cellphone handsfree going in the helmet to communicate speeds, but thats kinda stupid.
bugjuice
2nd May 2005, 10:45
Yeah the dyno should show the true speed (if it is a decent one) But this will only work on the back wheel. Older bikes have the gear drive for the speedo on the front. Only recent bikes with electronic pickup this will work on. Changing tyres or gearing will mess this up too.
A speedo healer will allow you to adjust this error on electronic units. Costs ~ $130Aus. Dunno if avail in NZ, Google one up.
Old world instrument technicians can fix mechanical instruments. Good luck finding one.
most bikes are running off the gearbox now. most newer bikes do, fewer and fewer are running off the front wheel, but doesn't mean you can bodge something together by sticking the front wheel on the rollers, then the back wheel of another bike next to it or something.. Depends on how keen you are to get it working I guess!! Do those rollers have no motors in them at all? Can't see why they would, but I've seen weirder..
Even new tyres compared to old tyres on the same bike can make a difference, but not a heap. The calibration will show the biggest difference, then everything else is a minor adjustment, unless you start playing with gearing and sprockets
Mr Skid
2nd May 2005, 10:47
Yeah the dyno should show the true speed (if it is a decent one) But this will only work on the back wheel. Older bikes have the gear drive for the speedo on the front. Only recent bikes with electronic pickup this will work on. Changing tyres or gearing will mess this up too.
I understand that in the case of front wheel driven speedos, if the rollers are wide enough, you can put the front wheel of the bike to be tested on the rollers and spin them with the rear wheel of another bike.
Drunken Monkey
2nd May 2005, 10:49
I could loan you my GPS, or get you to ride along side me for a short stint then we can compare indicated speeds. The GPS is pretty accurate, as long as it's a flat straight road and we hold our speeds for a few seconds for it to do its calculations.
Most brand new cars we've tested are doing 98 when indicating 100.
Most older cars are doing around 90-92 when indicating 100.
The error tends to be a percentage, not a fixed number, i.e. older speedos show 50 when you're doing 46 and show 150 when you're doing err, nah, we'll just flag that one, eh? You get the idea though.
Haven't tested many bikes with it yet.
I think the boys (Feint & Limmy) must have eaten too much Burger King??
:
even with the BK, still couldn't catch up to CRASHE! :whistle: :whistle: :ride: :msn-wink:
YES! crashe.. the 1st KB ride I went on (noob ride to wellsford) you stuck at 140 the whole time!... I think you are right about it being out.
Myself, Limmy and Madguitarist! aren't the only ones that think your speedo is off! hahaah :killingme :killingme
could go past a traffic copper at 110 and see if he pulls you over??!??! :laugh: :laugh: :laugh: (joking)
or ask a copper to laser you with his gun and you will know your speed. There are a few coppers on the site i think.... :whistle:
Lou Girardin
2nd May 2005, 11:02
Invest in a bike computer, as in bicycle, cheap as chips and dead accurate because you calibrate them to the front wheel rolling circumference. Mines within .5k. Then you've got cool stuff too, like top speed achieved, average speed etc.
inlinefour
2nd May 2005, 11:31
Hope there is no tickets in the post...
I'd start at the local motorcycle dealers for advice. :niceone:
crashe
2nd May 2005, 12:28
I could loan you my GPS, or get you to ride along side me for a short stint then we can compare indicated speeds. The GPS is pretty accurate, as long as it's a flat straight road and we hold our speeds for a few seconds for it to do its calculations.
Most brand new cars we've tested are doing 98 when indicating 100.
Most older cars are doing around 90-92 when indicating 100.
The error tends to be a percentage, not a fixed number, i.e. older speedos show 50 when you're doing 46 and show 150 when you're doing err, nah, we'll just flag that one, eh? You get the idea though.
Haven't tested many bikes with it yet.
Cheers, will do it when I am back up and running again.... in 2 months time....
As I do what the bike to be fairly accurate on the speed....
Oh no tickets guys.... :msn-wink:
Fit a hand held GPS unit to your handle bars (cable ties will hold it in place) and just ride. You'll soon see how your speedo compares to true speed.
Yep, I used a GPS to check my speedo, however I put it in the clear map pocket of my tank bag. (I'd borrowed the GPS from a mate, otherwise I'd loan it to you Crashe! )
You need a fairly long straight and flat section of road to get a reasonable reading off the GPS, but I found the NW motorway here in Auckland was pretty good for that.
My RF900's speedo is 10% optimistic (ie: reads 110 km/h for 100km/h). It is a mechanical front-wheel driven type.
I also checked my cars and found the Celica was 10% optimistic while the ancient EA Falcon SW was spot on!
F5 Dave
2nd May 2005, 12:59
most bikes are running off the gearbox now. most newer bikes do, fewer and fewer are running off the front wheel, but doesn't mean you can bodge something together by sticking the front wheel on the rollers, then the back wheel of another bike next to it or something.. Depends on how keen you are to get it working I guess!! Do those rollers have no motors in them at all? Can't see why they would, but I've seen weirder..
Even new tyres compared to old tyres on the same bike can make a difference, but not a heap. The calibration will show the biggest difference, then everything else is a minor adjustment, unless you start playing with gearing and sprockets
Well a Virago isn't that new huh?
The motor of the roller will spin fast enough to crash start the bike & that’s it.
Bodge the front wheel on the dyno while another bike drives the roller?
Are you soddin’ crazy! There’s a reason the bikes are slotted into the dyno with elaborate holders & tie downs. So you want to spin the front wheel up to say 100kph right next to the spinning rear wheel of a bike on a 1m roller?
Course if the bike touched the edge & gained traction it would drive off with a 100kph spinning front wheel. Fortunately most dyno operators wouldn’t allow this ‘bodging’, but please think before you suggest such a crazy idea lest we read about it in the next Darwin awards.
Fit a hand held GPS unit to your handle bars (cable ties will hold it in place) and just ride. You'll soon see how your speedo compares to true speed.I've got a GPS radar detector fitted to my bike, so I use it's display as my speedometer now...forget the stock one! That way I'm *always* riding at the true speed and not just the indicated speed. :Punk:
Ps. It also tells me in which direction I'm heading - N/S/E/W & NE/NW/SE/SW, not that I'm intending on 'getting lost down 22' or anything, eh guys?? :msn-wink:
the GPS is a good idea but expensive if you dont know someone with one. Originally I was going to get someone with a car to race me along the straight on the 22 with my cellphone handsfree going in the helmet to communicate speeds, but thats kinda stupid.Well you know 'of' me Pyro. Next KB ride that we're on together be sure to remind me about recording your "true" speed & I'll follow you with my GPS. Will I get out of third gear though?? :D jk.
Zed
You need a fairly long straight and flat section of road to get a reasonable reading off the GPS, but I found the NW motorway here in Auckland was pretty good for that.
Hmmm, that's not the case with mine! I use my GPS as my preferred speedometer when riding the bike. I watch it like a hawk on both residential and rural roads and it is usually spot on! I know this because I am often comparing the GSP to the stock speedo while riding and there is an accurate 8-10% variance in indicated speeds. There is certainly peace of mind knowing what true speed I am travelling, but I suppose that in times past being ignorant of the "calibration issue" and thinking that my speedo (in both cage & bike) was accurate had the same peaceful effect! :blink:
Hmmm, that's not the case with mine! I use my GPS as my preferred speedometer when riding the bike. I watch it like a hawk on both residential and rural roads and it is usually spot on!
Where's JRandom when you need him!? Remember a GPS is just calculating speed as distance/time between successive points on a plane surface. So depending on how often your GPS calculates its position, and how accurate it is at doing that (number of satellites visible etc), and if you are going around corners etc the GPS can be inaccurate too. I'd still recommend a flat straight road for calibration purposes.
Otherwise I was pretty impressed with how good a simple hand-held GPS was at tracking speed too.
pyrocam
2nd May 2005, 18:21
Well you know 'of' me Pyro. Next KB ride that we're on together be sure to remind me about recording your "true" speed & I'll follow you with my GPS. Will I get out of third gear though?? :D jk.
Zed
haha yeah man.
although I guess you could proberly do 130 in 2nd :D
Just a thought for the cheapest option.
How about finding one of those 5km speedo check areas and using a stopwatch?
bugjuice
2nd May 2005, 21:00
Well a Virago isn't that new huh?
The motor of the roller will spin fast enough to crash start the bike & that’s it.
Bodge the front wheel on the dyno while another bike drives the roller?
Are you soddin’ crazy! There’s a reason the bikes are slotted into the dyno with elaborate holders & tie downs. So you want to spin the front wheel up to say 100kph right next to the spinning rear wheel of a bike on a 1m roller?
Course if the bike touched the edge & gained traction it would drive off with a 100kph spinning front wheel. Fortunately most dyno operators wouldn’t allow this ‘bodging’, but please think before you suggest such a crazy idea lest we read about it in the next Darwin awards.
well you're no fun, are ya? :bleh:
haha yeah man.
although I guess you could proberly do 130 in 2nd :DProberly an "indicated" 130 (true 110ish) yes! But the idea is that I follow you...:ride:
F5 Dave
3rd May 2005, 09:29
My 750SP would do 140 in 1st! & still not be in the red.
I geared it down a touch as that was a bit silly for the road.
myvice
12th June 2005, 20:20
You could try Auck speedo services for calabration, he's on Newton Rd next to the Shell? station just down from Upper Queen St. Brake testing rollers only move @ 6kph or so, I'd get a pushbike speedo caus its cheep, weather-proof, small, comes with mounts for your bars and you can tell dickheads its a gage for your NOS bottle...AMPS has a dino (so I'm told) but I dont know if it has a speedo or not. Let me know how you got on caus my ones out too, about 10-20 ks too high so I'm not gunna lose sleep over it.
Biff
13th June 2005, 13:10
In my old car my speedo would read 90 MPH, the in car SATNAV would read 86MPH and the stickonthewindscreen GPS driven traffic/speed camera warning device (www.roadangel.com) would read about 93 MPH. So almost a 10 MPH discrepancy between the in-car GPS whatsit and the stickieonone.
After talking to my satellite guru buddies, asking them why the discrepancy between my car SATNAV and my Road Angel, they gave me all kinds of reasons why GPS isn’t necessarily the most accurate way of measuring speed (Doppler shift, multi-path interference, propagation issues etc).
The bottom line is - these boffins (and I mean real boffins as opposed to I know everything about anything cos I’m a cleverfockerpretenboffin) told me that it's a popular misconception that GPS is the be and end all to measuring speed accurately. That it’s only truly accurate when used in conjunction with other devices, such as gyroscopes etc.
We'll have to wait for the Galileo system to be fully operational before we can be more reliant on satellite positioning/speed/distance accuracy. Allegedly.
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