Speedo error

[Wild Rose]

Having just replaced my original Bridgestone BT023 tyres to the new Michelin PR4 GT, the speedo error is now worse
Previously with BT023 I had to do 106kpm to actually do 100kph by the GPS, But with the new Michelin PR4's I have
to be doing 109kph to achieve 100kph on the GPS 

What speedo error have others experienced with other brands ?
 
With only 230km on the Michelin PR4's so far I am very impresses with the feel of the new tyres but will report after doing some
decent Km on them 

[StinkyPete]

ST1300 with new PR3's

Speedo show 118km/h
GPS shows 110km/h

[Streak]

Having just replaced my original Bridgestone BT023 tyres to the new Michelin PR4 GT, the speedo error is now worse
Previously with BT023 I had to do 106kpm to actually do 100kph by the GPS, But with the new Michelin PR4's I have
to be doing 109kph to achieve 100kph on the GPS 

What speedo error have others experienced with other brands ?
 
With only 230km on the Michelin PR4's so far I am very impresses with the feel of the new tyres but will report after doing some
decent Km on them 

my speedo is almost perfect :) something about the police model being more accurate or something

[Biggles]

I've had +9% indicated with all the tyres I've used- BTs, Metzeller Z6 and three types of PRs (although I must admit I've not rigorously tested every situation, but check whenever I've got the GPS on the bike).

[pault]

for $20 bucks you can get a bicycle speedo. little digital thing. check if it will do more than 99.99kmh and that you can enter the exact circumference. This will give exact speed  and will  solve the problem of running 1300 sizes on 1100 bike.
Fiting sensor magnet can be tricky, have pics of method if any interest.

[HunterTodd]

On the Sydney Newcastle Freeway they have timing marks. You should do the 5 kay run in 2minutes 44 secs at 110 kays an hour. 

I have never checked the  bike but my Nissan work ute is more than 10 kays out! At least it reads over so I don't often get booked.

I have been thinking of trying one of those GPS linked HUD to see if it will work on the screen. Anyone tried it?

[Pezzz]

I have been thinking of trying one of those GPS linked HUD to see if it will work on the screen. Anyone tried it?

I think Wombat said he had bought a couple. Not sure on outcome as he went away for work but should be back now or soon or sometime......

[ST2UP]

Just checked mine and must say the speedo is extremely accurate, absolutely spot on !!!


The bikes speedo is sitting on Zero and so is the GPS and the bike is on the centre stand in the shed......cannot get anymore accurate than that 


But awaiting further reports on the PR4   

[Shaun]

Mine was out by about 9 kph at 110. GPS would say 110, analogue speedometer would read 119 or so.
It was worse when I was running low profile tyres, but I can't remember the exact figures.

[HunterTodd]

Just checked mine and must say the speedo is extremely accurate, absolutely spot on !!!


The bikes speedo is sitting on Zero and so is the GPS and the bike is on the centre stand in the shed......cannot get anymore accurate than that 


But awaiting further reports on the PR4   

Yeah I be thinking it would be hard to get booked like that as well!  Unless the Missus puts you in for loitering.

[Nigel]

Leo, I would have thought that unless you have changed Tyre sizes front/rear either or, it should not have changed what the speed o is recording. I went from Metz on the front and Bridgestone on the back to (correct sizes ) to a new pair of 023's of the same size and no change, as would be expected. Maybe your sizes have changed unknowingly?????? ???????Only thing that makes sense....Good Luck..

[Wild Rose]

Leo, I would have thought that unless you have changed Tyre sizes front/rear either or, it should not have changed what the speed o is recording. I went from Metz on the front and Bridgestone on the back to (correct sizes ) to a new pair of 023's of the same size and no change, as would be expected. Maybe your sizes have changed unknowingly?????? ???????Only thing that makes sense....Good Luck..

Standard size for the ST1300 120/70/18 front and a 170/60/17 on the rear
I don't know if you put a 180/55/17 on the rear would make any difference

I put a 195/60/15 on my car instead of the 195/55/15 the manufacture recommends now the speedo it totally accurate 

[Shaun]

Using different rated (eg lower profile) tyres will of course make a difference, as they have a different circumference due to their changed radius, you will be going a different distance per rotation, and your odo only tracks rotation, not distance.

[alans1100]

http://www.tacomaworld.com/forum/tirecalc.php?tires=170-60r17-180-55r17

[Shaun]

What he said ^ :)
Then, factor in tyre pressure. Small difference, but such small differences accumulate

[pault]

st2up post fails to mention he is on guyra time

[HunterTodd]

st2up post fails to mention he is on guyra time

So do we infer from that he is not stationary but actually going backwards. Relatively speaking.

[STroppy]

I bought and fitted a SpeedoHealer . . An easy job to install and calibrate and now speedo is accurate throughout the range however the odometer under reads . . . Not so good if you rely on it for distances, but good at time of sale of bike . . Lower odometer reading. You can adjust it easily for different size tyres.

[tj189]

Having just replaced my original Bridgestone BT023 tyres to the new Michelin PR4 GT, the speedo error is now worse
Previously with BT023 I had to do 106kpm to actually do 100kph by the GPS, But with the new Michelin PR4's I have
to be doing 109kph to achieve 100kph on the GPS 

What speedo error have others experienced with other brands ?
 
With only 230km on the Michelin PR4's so far I am very impresses with the feel of the new tyres but will report after doing some
decent Km on them 

sounds about right to me......mine is doing the same as yours on the Angel GT....  and was the same on PR3'3

[basadia]

I'm thinking about installing a speedo healer on my 1300 as the speedo is indicating 120 at GPS 110 k's. The one I'm looking at is here:
http://www.ebay.com.au/itm/Speedo-Healer-V4-0-Including-Harness-Healtech-Any-Model-Free-Delivery-/301864441348?fromMakeTrack=true

[johnnyYTED]

  I wonder if the ST1300 size PR4 I had put on before Perth has had any bearing on the speeding ticket I got.  will have to go for a ride down the freeway at 110 with the GPS speedo app on my phone...

[Lionel]

JohnnyYTED,
Speeding tickets are given out for exceeding the speed limit by less than 15 kph.
You were awarded a performance certificate for exceeding the speed limit by lots.

[Draco (Heartbreak Kid)]

  According to Shiney my Blue Beast is about 5kph out. @ 65kph is actually 60kph 

[basadia]

According to Shiney my Blue Beast is about 5kph out. @ 65kph is actually 60kph 

The problem with speedo errors is that get worse the faster you go, a difference of 5 ks at 60 could be 10 or 15 at 110 ks.

[Williamson]

My ST1300's speedometer is woefully inaccurate.  According to my GPS's, it under reads by around 5km/h to 10km/h (the faster I'm going, the greater the error).  If I never go over the posted speed limit (according to the speedometer), I don't think I would ever get a speeding ticket.

I'm on my third set of tyres now (current tyres PR4's), whilst these have all been the same size 170/60 - 17, all have been different makes.   I don't suspect they all been manufactured to the exact same dimensions, but I don't believe there has been any noticeable/tangible difference in the readings between the speedometer and GPS's.

Of course I'm assuming the GPS's to be accurate, but I believe my assumption to be well founded, because of speed checks (a few years ago now) at a number of VicRoads' overhead gantry speed check sites on the Calder Highway, Western Highway and Hume Highway - yeah I had two Navmans and one Tom Tom Rider mounted on the dash of my then current FG Falcon ute.  (The Calder and Hume Hwys speed checks are currently out of commission [busted], I suspect Marcus will tell us if the Western Hwy speed check is currently okay.)

Anyway I have confidence in the speeds indicated by the GPS currently on the ST (the Tom Tom) as I have passed countless roadside speed (err, road safety) cameras in a range of speed zones (50, 60, 70, 80, 90, 100 & 110km/h) with the motorbike speedo indicating 5 to 10km/h over the speed limit, and with the GPS indicating the posted speed limit or perhaps even 1 or 2km/h over the limit.  Never had a speeding ticket on the bike (touch wood).

Johnny, 

The way I remember your donation to the Police Ball is that it came about as follows - when stopped, you reckoned you may have been doing 121km/h (according to the speedometer), and you told the copper it may have been 120ish (by my reckoning your actual speed probably would have been around 112km/h).

However the copper alleged you were doing 131km/h, and if that was the case by reckoning your speedometer would have been indicating around 140km/h. 

Can't blame this on the tyres.