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Speedometer Accuracy

Vagabird

Vagabird

A wandering Bird
When I had an ÔÇÖ00 R1100 RT, more than a dozen LEOÔÇÖs in the US and Canada were courteous enough to check my speed with their radar and stop me to tell me of the results. How fast they thought I was going was always within 1 mph of how fast I thought I was going, so I figured my speedometer was dead on.

Now I have an ÔÇÖ07 R1200 RT. No LEOÔÇÖs have given me the same courtesy, but whenever I go through one of those places that have the radar-controlled sign (Your Speed Is), the sign shows that my speedometer is about 10% optimistic. Now, I know those signs arenÔÇÖt all that accurate, and I know that it is hard to get a good reading that way (IÔÇÖm usually decelerating), but it has gotten me wondering. If my speedo is 10% off, IÔÇÖm going to run my speeds up a notch.

Does anyone have any information on the accuracy of the R12 speedometer?
 
10% sounds close. Especially over 60 mph.
If I really want to know my speed I check the GPS.
 
My experience is just the opposite, and it is backed up by many anecdotal reports from others with GPS units.

The R11xx Oilhead series are notorious for speedometers reading as much as 10% high.

The R12xx Hexhead series has rather accurate speedometers, although it is standard practice in the automotive world to always err slightly on the optimistic side. This is to avoid the situation where a speedo is reading lower than actual, and a LEO takes notice, and a lawsuit against the mfg eventually ensues because the driver legitimately thought he was travelling at a lower than actual speed.
 
Mine is about 7MPH fast at 60MPH, so roughly 10%. That's according to my GPS, which I trust a whole bunch more than my speedometer.
 
My '06 is about 5% fast, reading 63 at a true 60. BTW, the instantaneous mph reading when re-setting the on board computer seems to be pretty accurate for both my RT and the last 3 BMW cages I've owned.
Tom
 
spot on

my '05 RT has been spot -on and verified by 4 LEOs in 3 states. Bless them all, they didn't feel the need to share their generiosty in a court of public record.

I was using the cruise control to boot. The dealer I bought the bike from told me the bike would probably read about 5MPH above actual; e.g, 65 for 60. Ummmm, nope. 75 is 75, 55 is 55, 35 is 35, and 40 is 40 for me.
 
Wow, lots of variances here.

My '08 shows a small positive differential from indicated to GPS. 60 indicated is 59 or so GPS. 80 is 76 GPS. I'm not smart enough to do the math, but I do know it's close enough that I don't have to be Einstein when I see a LEO & I don't have the GPS & V1 on the bike.

Like today, for example. FHP standing on the side of the road, in a construction zone, with LIDAR. I was in front of traffic, indicated six over, & didn't get a second look. :nod
 
I have a 08 R1200R, and a 06 Ducati Multistrada, both read aprox 10% fast, checked with a GPS. I also have a 75 R75/6 that I had the speedo rebuilt a few years ago, It also read fast before the rebuild, but it's pretty close now. I also have a Norton MK3, and a Yamaha Vision, and the speedos are dead on, cable driven, and have never been rebuilt.

Ken G.
 
My '05 GS reads about 1.5 - 2 MPH faster than my GPS on open straights. But those who trust their GPS must not ride where there are switchbacks in lots of dense tree cover. My garmin 276C with an external antenna often has me going speeds that I don't think the GS could hit riding over a cliff. The fastest I've seen was 747 MPH! I can rarely believe the "max speed" display for any given road trip.

I blame the stupid code in the GPS that assumes that you'll continue on the same heading when satellite lock is lost for a short while. That may work in Kansas but it doesn't work on mountain switchbacks. :deal

// marc
 
My '07 RT speedo shows about 2-3 mph faster than I am actually traveling, according to my GPS. It's fairly consistant across the speedo band. If I'm showing 40 on my speedo it shows 37-38 on my GPS. if I'm showing 80 on my speedo I'm showing 77-78 on my GPS
 
Speed

More concerned when travelling as I do not know LEO hangouts, so rely on Zumo as I suspect more accurate than speedo
 
vmi1991 said:
my '05 RT has been spot -on and verified by 4 LEOs in 3 states. Bless them all, they didn't feel the need to share their generiosty in a court of public record.

I was using the cruise control to boot. The dealer I bought the bike from told me the bike would probably read about 5MPH above actual; e.g, 65 for 60. Ummmm, nope. 75 is 75, 55 is 55, 35 is 35, and 40 is 40 for me.
Click to expand...

My '05 R1200RT is 'off' by 3%.

Shows 70 mph when in reality (radar and GPS), I am going 68.
 
My '06 12rt agrees with LEO

A LEO in Colorado clocked me at 76, and I had been running for about 20 minutes with the cruise set at just a hair over 75, in a 65 zone.

Glenn
 
'07 R1200r

Bike speedometer reads 4 mph faster than the two GPS units I've used. Both GPS have proven to be very accurate and currently trust Garmin Zumo 550. Being a newbee I took my new bike in for this and was told by the dealer that some are much as the 10% optimistic as mentioned here.
 
47512 said:
I also have a 75 R75/6 that I had the speedo rebuilt a few years ago, It also read fast before the rebuild, but it's pretty close now.
Ken G.
Click to expand...

I'm impressed as the '76 R75 I had (back in the day) read 125 when I got it up to it's honest top speed of 103 mph!
Tom
 
The speedos were probbaly about the same, at 70 mph it would read 77, the faster you went the worse it got. After the rebuild 70 indecated is alittle less than 72 mph, close enough for the old rellic. And closer than most of the newer machines I,ve had. And as I said in a previous post I have a 1975 Norton 850, the speedo is dead on. With the electronic speedos used on most motorcycles now there is no reason they cant be damn close.
Ken G.
 
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