Speedo not running true...

**FEINT** · 2nd May 2005, 11:00

Originally Posted by Zed

I think the boys (Feint & Limmy) must have eaten too much Burger King??

:

even with the BK, still couldn't catch up to CRASHE!

Originally Posted by tristank

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

could go past a traffic copper at 110 and see if he pulls you over??!??!

(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....

**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.

**crashe** · 2nd May 2005, 12:28

Originally Posted by Drunken Monkey

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....

**MacD** · 2nd May 2005, 12:37

Originally Posted by Jantar

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

Originally Posted by bugjuice

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.

**Zed** · 2nd May 2005, 15:16

Originally Posted by Jantar

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.

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??

**Zed** · 2nd May 2005, 15:25

Originally Posted by pyrocam

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??

jk.

Zed

**Zed** · 2nd May 2005, 15:43

Originally Posted by MacD

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!

**MacD** · 2nd May 2005, 16:19

Originally Posted by Zed

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

Originally Posted by Zed

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??

jk.

Zed

haha yeah man.

although I guess you could proberly do 130 in 2nd

**idb** · 2nd May 2005, 20:38

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

Originally Posted by F5 Dave

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?