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Topic: How accurate is your speedometer ?  (Read 1314 times)

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David Morrow
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« on: May 21, 2018, 09:46:40 pm »

I could use a bit of help from the forum members.

For the last 15 years, I've been riding my 2003 Yamaha FJR. ( I imported it to Canada from the U.S.) The speedometer is spot on accurate when I have compared it to two different GPS's and probably hundreds of those road side radars that we all see when entering small towns and construction zones.

A couple of weeks ago, I bought a new 2016 FJR ES. I found that the speedometer is reading 8% high. In my readings on one of the FJR forums, it would appear that this is quite common but more so among Canadian bikes. I contacted Yamaha Canada who confirmed that "all manufacturers do this" and that the error can range as high as 15%; always high, never low.

I have created a Google sheet to compile some info on the issue. I started by taking out both my bike and my car and, with the GPS and vehicle speedo in close proximity, I took some video to document the speed readings side by side.

If anyone would like to help in my endeavour, I would like actual measurements done with your bike at speed; not based on your recollection. I would like you to take your measurements at 60 MPH / 100 Km/H or as close as possible to that. It's also important that the measurements be made on tire sizes as specified by your bikes manufacturer. My GPS has been really accurate so I am comfortable with its readings for this comparison. I realize that this could be an issue so I am making a broad assumption that your GPS will be as accurate as mine. ( I am going to see if I can get a local cop with a radar gun to verify my GPS's accuracy. )There will undoubtedly be some error due to tire wear but I don't think it will be material. If you would like to tell me what % wear is left on your tires, that would help if I start to get really fussy with the math and try to account for that. Do the measurement in your car as well if you are so inclined. All readings will be appreciated.

Please leave your details in your replies here on the forum instead of by private message so that everyone can follow along.

Here is the link to the Google Sheet. That will tell you what details I am trying to gather.
https://docs.google.com/spreadsheets/d/1kAjfMknSwxwkQtz-RorCFHfsvbnpUIB4hqsqBMIDAoY/edit?usp=sharing

There is all  kinds of room for discussion on the whys and wherefores as to why bike manufacturers do this but my understanding is that they consider it a safety issue so that us children don't ride faster than we really should. I'd like to save that discussion for later and just collect the data for now.





« Last Edit: May 21, 2018, 10:39:41 pm by David Morrow » Logged

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kyzrex
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« Reply #1 on: May 21, 2018, 10:00:11 pm »

My 2007 Yamaha FZ6 and my 2014 Kawasaki Ninja 650 are both 2-3 mph optomistic at what the GPS says is actually 60.
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« Reply #2 on: May 21, 2018, 10:29:50 pm »

My 06 Hayabusa reads 4-5 miles above the actual speed.  Surprisingly my 1979 Honda CBX is spot on at all speeds.
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jay547
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« Reply #3 on: May 21, 2018, 10:36:18 pm »

My FJ-09 is approximately two mph above.
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David Morrow
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« Reply #4 on: May 21, 2018, 10:41:35 pm »

While I appreciate your responses I need real world measurements done with your GPS and speedometer at the same time, side by side. It'll give you an excuse to go for a ride too.
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« Reply #5 on: May 21, 2018, 10:50:20 pm »

I got the two mph difference by checking against my gps and I use the proper sized tires.
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« Reply #6 on: May 22, 2018, 06:54:27 am »

I got the two mph difference by checking against my gps and I use the proper sized tires.
Dave, he's obsessive-compulsive about it. He needs you to REALLY inconvenience yourself to satisfy himself that motorcycle  speedos are generally inaccurate. 😏 (Something we've all discovered and accepted years ago...)
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« Reply #7 on: May 22, 2018, 10:50:51 am »

I don't have GPS. What I do have is a careful measurement of the accuracy of the speedometer and odometer on my 2014 Yamaha FJR A. I have always run stock sized tires (Michelin PR-4s) with specified iar pressures in both.

I ran a measured 10 mile course on level ground with the cruise control set at 60mph. I did this several times to make sure there were no variations from run to run. I also checked the accuracy of the odometer at the same time. The measured course was Highway 101 north of Ukiah, California (level, very light traffic if any). Caltrans has mile markers at every mile to use as a reference.

I found both the speedometer and odometer to be 2% optimistic. 60mph indicated measured 58.8mph (using a stopwatch to clock the speed). Same with the odometer, 10 miles on the measured course resulted in a reading of 10.2 miles. So the 40,000 miles on my odometer is actually 39, 215.7.

Hope this helps.

Dan
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« Reply #8 on: May 22, 2018, 01:29:44 pm »

I ain't got no stinkin' GPS.

I have always suspected that my 2012 FJR1300 was way high on the speedometer reading. Curiously, I find that the odometer is fairly close. On the trip I just got back from I checked on one of those radar thingies on the side of the road. My reading was 4/5 MPH high.

Sorry I can't be of more help.
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« Reply #9 on: May 22, 2018, 01:39:11 pm »


While I appreciate your responses I need real world measurements done with your GPS and speedometer at the same time, side by side. It'll give you an excuse to go for a ride too.


Thought that’s what I gave you.... Headscratch
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« Reply #10 on: May 22, 2018, 01:56:22 pm »

It is standard for a motorcycle speedometer to be calibrated in such a way that it displays a speed faster then the actual speed of the bike. It has been written about numerous times. Here are a few sample articles on the subject:

https://www.popularmechanics.com/cars/how-to/a3127/4260708/

https://www.superstreetbike.com/are-speedometers-accurate-mythbusters

https://www.sportrider.com/how-to-fix-calibrate-inaccurate-motorcycle-speedometer

Cheers,

Kai

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« Reply #11 on: May 22, 2018, 02:15:00 pm »

DM,

What do you plan to do with this data?

There is no way I am going through the effort of documenting what I already know.  My speedo is about 7% high.  I really don't care.

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« Reply #12 on: May 22, 2018, 06:16:30 pm »

My Nav V GPS shows a difference of 3% at 100 kph with the speedo showing 103 kph.
That is with new Michelin PR4 GTs (OEM) on my 2016 BMW R1200RT.
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« Reply #13 on: May 22, 2018, 09:30:48 pm »

My ‘16 FJR A reads about 2mph fast at 75mph. It was off slightly less when the tires were brand new, and gets worse as they wear, obviously.  My 2007 ST1300 was 7-8% fast.  

For me the FJR is good enough.  For the ST1300, however I invested in a SpeedoHealer and adjusted the speedo -7% to put it closer to reality.  This also made the odometer (which was originally accurate) read 7% shy on mileage - but hey.   Twofinger
« Last Edit: May 22, 2018, 09:37:36 pm by naustin » Logged

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« Reply #14 on: May 25, 2018, 01:24:43 pm »

2008 Yamaha FZ1.  At 110 kph it read 116.  I had the ECU reflashed by Vcyclenut and he adjusted the speedo as well. Now at 110 it reads 109.
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« Reply #15 on: May 29, 2018, 03:14:32 pm »

Last weekend I tested my new-to-me 2013 R1200RT with the Garmin GPS I used to use in my car. It indicates +2mph fast (40 indicated=38 actual) consistently up to 80mph indicated where its actual is 77mph. I didn't test it any faster than that as I don't really ever go that fast or, when I do, I'm not really concerned about accuracy as I'm getting arrested one way or the other anyways.  Lol
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« Reply #16 on: May 31, 2018, 05:58:03 pm »

I just added this, mounted on my bars... $25 or so, plugs into micro USB, and it's much easier to read while riding.

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« Reply #17 on: June 02, 2018, 11:30:50 pm »

My 08 Bandit was 7.3% off.

Installed a Speedohealer. It is now 100% accurate.
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« Reply #18 on: June 04, 2018, 10:55:59 pm »

I have two bikes. The bandit 1200 is a 2002 and its speedo is off by about 7-8%. The BMW was new to me last year so I have a direct comparison. 2004 R1150RT with stock tires. The rear has about 80% left and the front about 40%. The speedo at 60 mph measure 54 mph on both my Garmin Nuvi 550 and on the speedometer app on my phone. That 10% is consistent above about 40. At least the 10% allows me to do the math in my head. The bandit I always guess at about 5 mph high but I usually have the GPS running to show my true speed on both.
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