BMW K1200, K1300, and K1600 Forum banner

Estimate of how much over the speedo is?

2K views 15 replies 15 participants last post by  beavtm 
#1 ·
I am riding a K1300GT this weekend in Norcal. In the region of 50-80mph, how high does the speedo read? I am used to my LT's 5mph, and knowing this I can sit just under 10 over on the freeway sections, with some surety that the cops won't stop me.

Not so concerned once I hit Hwy 36! and the Wild Rivers loop :)

Oh boy, this is going to be a fun weekend.

TIA.
 
#4 ·
My '07 is within 1 mph of the gps all across the range (at least up to about 150 or so). It's also within 1 mph of those random "Your Speed Is:" signs that I sometimes come across at more sedate speeds.

I also ran the odo check over a 100-mile straight stretch of road (what else are you supposed to do on the boring bits of I-5?). The odo was less than 2/10's off over the whole distance.

Of course, than can shift slightly with different tire brands, but it's a damn sight closer than the LT ever was.

Enjoy 36. That's an awesome road, and still one of my favorites. :ricky

 
#7 ·
Mine seems to be somewhere about 2 to 3% faster than the gps above 40 or so. I've gotten so used to looking at the Zumo though I hardly ever look at the speedo any more.
 
#9 ·
larrykay said:
My 1300Gt is about 2 to 3 mph over at 80mph and 3-4 over at 110.
Similar to my K1300R. I had a race logic (professional race logging system) on it while over at the Nurburgring, and found:
30mph = 5mph over
50mph = 3mph over
100mph = 4 mph over
125mph = 3mph over
150mph = 2mph over
170mph = 1mph under

I suspect speedos are all a bit different, even on the same models. Speeds above are of course approximate (as a rough conversion from metres per second the race logic gives you, plus I obviously had to eye-ball the speedo).
 
#13 ·
According to the roadside radar signs my 06 is spot on.....but can one trust those things.
I don't have a GPS....yeah old school here.

Past history though prior to GPS.....

A friend and I asked another friend who is a California Highway Patrol officer if he would radar gun us on our bikes to test our speedos. We went to a secluded road and with one riding ( a Honda ST100 and my K1100RS) and the other taking notes next to the CHP radar we noted the speedo versus the radar at 10mph increments. On BOTH bikes at all speeds the speedo was 10% higher than the actual reading on the radar.
As a aside the CHP officer would actually call out the speed by eye before bringing up the gun to shoot the bike. He was right on each time. I guess decades of doing it for a living made him pretty damn accurate.
 
#14 ·
My 2007 K1200GT speedometer reads approximately 5-10% higher than actual, when compared with the "Your speed is..." radar traffic signs on the side of the road.

On a related question, does anyone know the accuracy of the GPS speedometer displays? Are they within 1 mph of actual, for example? Do they take into account up and down slopes, where the road distance and the "projection" distance differ?
 
#16 ·
XMagnaRider said:
On a related question, does anyone know the accuracy of the GPS speedometer displays? Are they within 1 mph of actual, for example? Do they take into account up and down slopes, where the road distance and the "projection" distance differ?
There is a margin of error but for practical purposes it's negligible. The trick is how the manufacturer of the GPS device calculates the speed. They have altitude information but do they use it to calculate speed for slopes, it's your guess. With most it fall's into the noise as well (unless you are falling off a cliff). If the position is off by 'x' feet, that value will be fairly consistent unless you loose line of sight (position due to tunnels, obstructions like tall buildings, or number of vehicles in range). Most GPS devices only display MPH with no decimal place, therefore you can assume a 1 MPH margin of error depending how the manufacturer handles the remainder (round up or down, cut off, ...).

So in effect your mileage may vary but it's all about how the software was written in the user equipment.
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top