Speedometer error ?

[oblertone]

I recently had the opportunity to measure my 1100GS speedo reading against that of a 'job' bike with a calibrated speedo, the results were something like :-

Actual 30mph - Indicated 36
Actual 40mph - Indicated 48
Actual 50mph - Indicated 62
Actual 60mph - Indicated 74
Actual 70mph - Indicated 85

I knew it was reading optimistically but this much variance is a joke, has anyone got a solution ?

Paul

 

[MikeO]

has anyone got a solution ?

Paul,

R1100R Speedo drive (2.875:1 - stamped 2.9, for some reason )

This corrects the speedo to within 2% - cross checked with GPS.

It also makes your bike do fewer miles per gallon, makes it slower, but means you don't have to service it so often.....

Mike

ps Do a search for 'speedo drive' and you'll probably find more detail if you need it. Someone (JimB?) managed to get his dealer to fit the more accurate drive foc - never occurred to me - dammit!

 

[~Stef~]

I recently had the opportunity to measure my 1100GS speedo reading against that of a 'job' bike with a calibrated speedo, the results were something like :-

Actual 30mph - Indicated 36
Actual 40mph - Indicated 48
Actual 50mph - Indicated 62
Actual 60mph - Indicated 74
Actual 70mph - Indicated 85

I knew it was reading optimistically but this much variance is a joke, has anyone got a solution ?

Paul

I recently fitted a VDO (bicycle) trip computer (from Halfords) to my GS I got diffferences in MPH between it and the O/E speedo, though not as inaccurate as those of yours.

~Stef~

 

[MikeO]

Re: Re: Speedometer error ?

I recently fitted a VDO (bicycle) trip computer (from Halfords) to my GS I got diffferences in MPH between it and the O/E speedo, though not as inaccurate as those of yours.

~Stef~

How do you test the accuracy of your VDO?

Mike

 

[richie]

The bike speedo should be pretty acurate as it is up to the installer to measure the circumfrence of the wheel that it is connected to. It is after all a precise electronic device!

 

[Dave Hall]

I`ve given up on the mechanical speedo and bought a Touratech IMO (see MIGSELs photos .here).
Apart from all the other goodies on it is the facility to enter the circumfrence of your wheel to calibrate it.
I put a rough figure in and then calibrated it VASCAR style on the Countys measured mile. Its brilliant.
Another feature I like is the ability to press a couple of buttons as I roll off the ferry and it reads KPH.

I tried a VDO cycle computer but found the display a bit small for my old eyes

 

[Deak]

Speedo error

Don't think that speedo error is unique to the GS. My brothers VFR has the same percentage error as my 1150 with identical speedo readings at 40, 75 and 100mph (wasnt able to compare at 140!).

Oddly on a 2500 mile trip to Spain and back they also returned identical (to within 0.5 of a mile to the gallon) fuel consumption.

 

[Dave Hall]

I`ve found a similar level of speedo error on my wifes new Focus when checked using GPS however the odometer error was negligable (0.01%) on the Focus but on the GS it reflected the same error as the speedo.
The only reason I can think of that would cause that is if there were two sources of data which seem strange.

 

[roadrider]

Strange

I`ve found a similar level of speedo error on my wifes new Focus when checked using GPS however the odometer error was negligable (0.01%) on the Focus but on the GS it reflected the same error as the speedo.
The only reason I can think of that would cause that is if there were two sources of data which seem strange.

Dave you've quessed correctly. when fords & others moved to digital led display for the milage, the speedo was still mechanical, and although the speed is now pulse sensed, the 2 source setup still applies, (another strange but true factode)
John

 

[GuidoT]

I just went out and checked the speedo of my '98 1100 GS against my GPS. It wasn't anywhere like as bad as that of Paul's, but it was basically 5MPH fast from 20MPH to 90MPH. 20MPH was an indicated 25MPH. I was expecting a percentage error, but not a constant one.

I used to use a Sigma cycle computer on my Guzzi, which was very accurate and probably cheaper than a R1100R speed drive. Tho' it does lack the presence of Dave's Touratech IMO.

-- Guido

 

[Dave Hall]

I just went out and checked the speedo of my '98 1100 GS against my GPS.

The GPS system can give you some odd readings like going up and down hills will affect them and as your GPS refreshes once a second then higher speeds will not be as accurate.

 

[GuidoT]

You're right, it isn't very good on the twisties. But on boring flat staight roads at a constant engine speed it should be OK. It usally matched the speedo and bike speedo on my Guzzi. But, it can get confused at times. I once had a reading of over 100MPH whilst sitting on a rock in Glencoe., but that was before SA? was turned off.

Whatever, this all bodes well for the use of GPS for controlling vehicles speeds in speed limits.

-- Guido