GPS vs SPEEDO - Page 2 - Stromtrooper Forum : Suzuki V-Strom Motorcycle Forums
General V-Strom Discussion Talk about all things V-Strom not limited to just one of the above models

 10Likes
Reply
 
LinkBack Thread Tools Display Modes
post #11 of 31 Old 10-20-2019, 10:24 AM
Stromthusiast!
 
Join Date: Dec 2018
Posts: 221
The why mc speedos are off is curious. The commonly stated 'the mfr's don't want the rider to be going faster than the indicated speed' makes no sense at all. The last two cars I've owned were dead on - as checked w/ a stop watch at 60 and 70 and comparing to a GPS. Odo's are usually a lot closer to the actual distance traveled, but they will be off a little depending on tire brand (size) wear (size) gearing (did you change the front sprocket?) or even if you changed the wheel size.

If you want to know what your odo error is, get on an interstate, pull up to a mile marker and set the trip odo to 0.0, then ride for 10 miles (mile markers). Pull alongside the marker and note your indicated reading. You can buy a speedohealer (there are a couple of brands) and correct either the speedo or odo but not both at the same time. The surveyed mileposts are pretty accurate. If you go by the mileage shown on a GPS that might be a bit off because your GPS measures distance in straight line segments and adds them up. The distance shown might be shorter if the road curves a lot.
Ratchet is online now  
Sponsored Links
Advertisement
 
post #12 of 31 Old 10-20-2019, 10:36 AM
Stromthusiast!
 
Join Date: Mar 2011
Location: Pasadna area
Posts: 13,915
The Speed indications is nice to avoid getting a citation for exceeding the posted limit. The odometer is nice to know how far you have traveled but in the long run, say 100K miles, does some small amount of error really make any difference? So the bike lies a bit and you don't get the 100K award until you've gone 100300 miles. Is it really that important?
Most riders won't ride that far during their warranty period so distance is a moot point.
If you demand such accuracy I suggest moving to a different dimension. Oh, and don't get a red bike, the paint will fade.

Rachet, I don't think the LEO's want you stopping on the interstate to play with your speedo. I've done the cursory check for years out on the interstate. I finally realized it doesn't really matter.
ocoas likes this.
notacop is offline  
post #13 of 31 Old 10-20-2019, 11:42 AM
Stromthusiast!
 
ocoas's Avatar
 
Join Date: Jan 2015
Location: Central Cal
Posts: 277
I had a BMW that’s speedo was off by a lot. I took the bike in to have it repaired under warranty. I was told the speedo was within BMWs spec. 5% plus 5mph. Mine happen to be off by the full amount.
The speedo was less off at slow speeds, up to about 30 mph it was off by 5 mph but when the speedo said 100 mph I was actually going 87 mph.
I ended up mounting a GPS and relied on it.

I was also told that the speedo and mileage on the newer odometers were controlled by computers and therefore the speed could be off but the mileage was within a percent or two.

In the big picture accuracy is for bragging rights and doesn’t really effect my daly life.
ocoas is offline  
 
post #14 of 31 Old 10-20-2019, 12:54 PM
Stromthusiast!
 
Join Date: Mar 2011
Location: Pasadna area
Posts: 13,915
Ocoas, One of the points of interest at BMW rallies, before electronic speedo's, was to go around and see what the mileage was. It was bragging rights to an extent. You may have a bike a few years old but how many miles had you gone in that time. It was observed during a promenade about the rally site with a beer in hand checking out the bikes.
Not the same no mo, key off and the bike gives no indication of use.
The old round mechanical speedo's could be adjusted. Just remove the needle and reposition it with a change of spring tension. I got the speedo on my 750/6 dead on at one point. That was doing the measured interstate mile and minding the clock and distance. But the old speedo's were subject to mechanical failure too. So it may be accurate only for a while. There were a couple places folks would send their speedo to for repair. I gave up when the local place had two whacks at the odo on my R65 and it still failed.

Last edited by notacop; 10-20-2019 at 01:19 PM.
notacop is offline  
post #15 of 31 Old 10-20-2019, 01:04 PM
Stromthusiast!
 
OydnaR's Avatar
 
Join Date: Jun 2016
Posts: 1,777
Quote:
Originally Posted by Ratchet View Post
The why mc speedos are off is curious. The commonly stated 'the mfr's don't want the rider to be going faster than the indicated speed' makes no sense at all. .
I could google search and post a link. It stems from a EU regulation that fines the mfr's if they read slower than you are actually going, to cover their asses, they make em read high. Most imports are setup to meet EU regs, I believe that Harley speedos read correct

IBA#9560
Copyright (c) 2019
OydnaR is offline  
post #16 of 31 Old 10-20-2019, 01:07 PM
Stromthusiast!
 
Coach23101's Avatar
 
Join Date: Oct 2017
Location: Seattle in the summer and East Cape, Baja in the winter. Perfect!
Posts: 340
Garage
DigitalHUD (or any other free app) replaced my speedo and I don't even think about it anymore.
Other than to think that a speedo should work properly. Period. And the fact that so many don't is just nuts.
RLBranson likes this.
Coach23101 is offline  
post #17 of 31 Old 10-20-2019, 01:14 PM
$tromtrooper
 
Stalky Tracker's Avatar
 
Join Date: Dec 2005
Location: Sconsin, USA
Posts: 3,998
Garage
Quote:
Originally Posted by OydnaR View Post
I could google search and post a link. It stems from a EU regulation that fines the mfr's if they read slower than you are actually going, to cover their asses, they make em read high. Most imports are setup to meet EU regs, I believe that Harley speedos read correct
To expand on OydnaR's post, from Cycle World:

"On testbikes we typically see an error of a few percent in the speedometer reading—at times up to 10 percent and always on the high side. This fudge factor can most likely be traced to ECE Regulation No. 39, which is a 14-page document detailing speedometer accuracy for vehicles sold in EU countries. According to this law, a speedometer can read high by as much as 10 percent plus 4 km/h at a specified test speed, but under no circumstances can the speedometer read low.

Speedometer accuracy is very dependent on tire diameter, which is affected significantly on a motorcycle by pressure, load, and temperature. These values are strictly defined in the regulation's testing procedure, and the speedometer calibration must take these potential alterations into account. In addition, the manufacturers must consider the owner changing to non-standard tires, which may have a different diameter than the OEM fitment. In our last tire test, diameter of the seven rear tires tested varied by 2 percent, which directly affects the speedometer by the same amount. This also accounts for some of the discrepancy. Even with all these variables, however, the manufacturers do seem to be erring on the side of caution so the speedometer doesn't read low."



The link: https://www.cycleworld.com/sport-rid...e-speedometer/
richlandrick likes this.

2020 Eastern V-Strom Rally (website) - May 14 - 17, 2020
__________________________________
2006 Suzuki V-Strom DL650K
1986 Honda Shadow VT700C
1974 Suzuki TM-250
1966 Triumph Bonneville T-120R
1965 Suzuki 80
Stalky Tracker is offline  
post #18 of 31 Old 10-20-2019, 03:39 PM
Stromthusiast!
 
PineLaneRider's Avatar
 
Join Date: Aug 2016
Location: South Central PA
Posts: 363
Garage
I'd rather use my phone/GPS as my speedo; it's bigger and easier for me to see, and have an accurate odo. I use Ulysee speedometer app on my phone. To each his own.
PineLaneRider is offline  
post #19 of 31 Old 10-21-2019, 11:08 AM
Stromthusiast!
 
Motorpsychology's Avatar
 
Join Date: Oct 2018
Location: Prescott, Wi. Upper Ms.River bluff country
Posts: 363
Garage
Post You Do The Math.

Quote:
Originally Posted by Brockie View Post
Always trust the GPS reading. I understand that vehicle manufacturers are obliged to ensure that they never understate your speed, and so they make sure of it. My DL650 consistently reads 108km/hr at a true GPS 100km/hr
The Global Positioning Satellite system is a constellation of satellites orbiting the Earth in a geosynchronous orbit; they stay over the same place as the earth turns, in other words- same as other sat-com satellites. At any given time, a gps unit is reading 8-12 satellites and triangulating your location to within a meter or two, and your device compensates for calculation time.
US-market speedometers in the late seventies-early eighties were mostly quite accurate, as in those days the infinitely wise USDOT mandated all speedometers display no more than 85mph,and the readout was calibrated much more accurately. Apparently, the thinking was that if you don't know how much over 85 you were going, you wouldn't attempt to. Anyway, my '80 Kawasaki KZ750 speedo is right on with a newish front tire (pickup gear drive cable-driven from front wheel) checked with a first-gen Garmin e-Trex
I think the manufacturers err on the side of caution to allow for alternative tire profiles/sizes.

"It is amazing what you can accomplish if you are not concerned with who gets the credit"- Patrick Griffin
"I never said half of that stuff."-Confucius
Motorpsychology is online now  
post #20 of 31 Old 10-22-2019, 10:31 AM
Stromthusiast!
Junior Trooper
 
Join Date: Jul 2019
Location: Temecula, Ca
Posts: 5
Quote:
Originally Posted by Motorpsychology View Post
... US-market speedometers in the late seventies-early eighties were mostly quite accurate, as in those days the infinitely wise USDOT mandated all speedometers display no more than 85mph,and the readout was calibrated much more accurately. Apparently, the thinking was that if you don't know how much over 85 you were going, you wouldn't attempt to. ...
I had an '81 Honda 750F with the 85 mph limited speedo. I could bury the speedo in 2nd gear (exceed the 55 mph limit in 1st).

Also, I did some number crunching and found that changing the front sprocket up one tooth puts the speedo almost right on the GPS reading - especially so at higher speeds.

Attached is a screenshot of the spreadsheet I made showing how gear ratios affect final speed and indicated speed. I can't attach the original file (.xlsx) but if you want it I can email it to you or find some way to make it accessible...

Since most of my riding is pavement or graded dirt roads I really like the new gearing!
Attached Images
File Type: png Gear ratios.PNG (45.4 KB, 9 views)

Chasin' the yellow ribbon
tsrDave911 is offline  
Sponsored Links
Advertisement
 
Reply

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the Stromtrooper Forum : Suzuki V-Strom Motorcycle Forums forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:
OR

Log-in










Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page
Display Modes
Linear Mode Linear Mode



Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome