Speedometer error for '07 R1200RT

[Twisties]

Hi,

 

Found and read the thread regards speedometer error on '06 RTs from last summer. Great thread guys.

 

Here is my situation and questions:

 

My RT is scheduled for it's 600 mile service tomorrow. I called to day to make sure they would have time to fix the speedo. There are two permanent radar installations near me, and both indicate that I am going more than 10% slower than the indicated speed on the speedometer.

 

I've made two passes on one installation and gotten (all numbers in mph) 31 when 36 was indicated on speedometer, and flashing between 30 and 31 when 35 was indicated on speedometer. At the other installation I got 35 when 40 was indicated on the speedometer. If the average error is 5 and the average speed is 36-37, then this is 14% error.

 

So, here is what the dealer had to say: There is a service note/memo/something out from BMW acknowledging the problem for all but RT-Ps and indicating that it is not a fault but rather a safety feature, and not to be repaired. I said that's unacceptable, and he agreed, saying that everyone at the dealer believes BMW should address the issue.

 

My questions:

 

1. It really is unacceptable, what should I do to most easily get it resolved?

 

2. Anyone know how to find these service bulletins, memos, or whatever they are, I'd like to see this thing and find out if this much error is allowed?

 

3. Anyone have a calibration procedure (not a check procedure, saw a great check procedure in the July '06 thread), but a procedure to actually reset the thing myself?

 

Thanks so much in advance!

[Twisties]

Oh yeah, one more question:

 

Is this error absolute or relative, e.g. at 75 indicated speed will I really be going 70, or 64?

[Mudman]

As trained by BMWNA the allowable speedometer error is 10% + 2.4 MPH. Any error less than this is not covered by warranty and considered acceptable. The speedometer is always set to read low to provide assurance you will not be traveling faster than indicated with the variety of approved tire dimensions. I think you will find the odometer reading is much closer to actual distance covered.

 

Hope this answers your question

[bobbybob]

Have you measured the speed using a GPS? My 07 RT reads 1 mph slow at 35, 2 slow at 70--according to gps.

[CTRBLNCD1]

As trained by BMWNA the allowable speedometer error is 10% + 2.4 MPH. Any error less than this is not covered by warranty and considered acceptable. The speedometer is always set to read low to provide assurance you will not be traveling faster than indicated with the variety of approved tire dimensions. I think you will find the odometer reading is much closer to actual distance covered.

 

Hope this answers your question

 

That is the correct answer....Every BMW, heck almost every motorcycle, has some amount of speedo inaccuracy. Simply ride on and don't worry about it.

[Twisties]

Mudman, thanks for the input!

 

So the bike is at the dealer's now. I talked to head of service, he said they are set 6% low, and supposed to be within 5 mph of that.

 

I asked what it would cost for me to pay to have what I consider to be a serious defect (going 64 when it reads 75 will get you killed (shot or run off the road) around here) repaired, even though it should be covered under warranty. They don't know how to fix it and are looking into it.

 

Incidently, my bike came with Bridgestones, my wife's Metzlers. Her bike reads within 2 mph of actual. The dealer says part of the reason is to account for the different tires that are within the recommended range of tires.

 

Ctrblncd001, thanks for your opinion, but I have to disagree. The July '06 thread on '06 RTs seems to indicate that most respondents found their speedos within 1 to 2 mph at all speeds. I don't need it spot on, but I've never had any vehicle anywhere near to this far off. This is to the point of why have a speedo to begin with.

 

Bobbybob, I don't have a gps. I'd get one but have no interest in it in general. Maybe I can borrow one. My concern is to know what speed I'm really going, so if I can figure an appropriate correction regime for my speedo, that would do.

 

My opinion is that the instrument (speedo) should give you accurate information, and it should be up to you to decide what you are going to do with that info.

[JustKrusen]

Ride on the interstate and use a stop watch to time yourself from mile marker to mile marker. See how many seconds it takes to cover the mile. Te first column is the driving seconds and the second column is your actual mph.

 

seconds-----mph

 

65----------55

60----------60

55----------65.5

50----------72

45----------80

40----------90

[Mudman]

I agree all the instruments should be accurate, but for liability reasons and tire circumference variations the speedometer is necessarily set to indicate low.

 

This is also true with many so called certified speedometers. In the last century as a police motor we checked the calibration of our speedometers with the aid of a AAA mobile calibration trailer. Our Kawasaki police motors were often off by 10% in some of the speed ranges. A card was issued showing the variations so we could adjust our speed readings for speed enforcement and court hearings. At no time did the speedometers get adjusted. If a "customer" inquired about the accuracy of our speed measurement we would present the calibration card.

 

It was also fun getting the calibrations taken with front wheel speed drives. One motor would slowly bring the rollers up to 85 MPH using his engine to bring the rollers up to speed with his rear wheel while the officer being calibrated had his front wheel on the other side of the same rollers. It was pretty important to slowly bring the speed back down!

 

You would have it a lot better if you decided to calibrate your speed with a similar rig, You could do it alone powering the rollers with you rear wheel that also takes the speed signal. If you really want to know how accurate your readings are you might check the schedule of the AAA mobile calibration trailer. I understand this is free for AAA members.

 

Short of all of this I would suggest a GPS reading which would be fairly accurate.

 

Keep in mind as you approach a speed reading trailer your speed is actually read lower than your true speed due to the cosign effect of an increasing path difference between your bike and the radar signal as you get closer. The most accurate radar reading will be travel straight on to the radar which is realized at a fairly long distance from the trailer on the side of the road. This distance reading is more difficult on a motorcycle due to it's small reflective area. Often the radar will be reading a larger vehicle behind you such as a truck due to it's relatively larger return signal until your closing distance becomes the stronger return signal. Add to this that traffic radar only reads in whole numbers. If you being read at 34.9, the radar will read 34 MPH until you cross the threshold of 35 MPH.

 

Probably more than you wanted to know, but there is a possibility your speedometer error may be less than you thought. My 96 RT was off by 5 MPH at 60, but my current RT is off by only 2 MPH at that speed. The error on both of these bikes seems fairly proportional to the speed traveled.

 

[TomfromMD]

My concern is to know what speed I'm really going, so if I can figure an appropriate correction regime for my speedo, that would do.

My opinion is that the instrument (speedo) should give you accurate information, and it should be up to you to decide what you are going to do with that info.

For what it's worth, the computer on my '06RT as well as the ones on recent BMW cages I've owned have all been spot on for instantaneous speed. If your dealer cannot calibrate your speedo properly, this may help establish the baseline error at various speeds.

While I agree that instruments should be as accurate as possible, that isn't always the real world case. My 1976 BMW R76/6 read 124 at it's true top speed of 102 - a 20%+ error which was similar to that of many Ferraris of that vintage.

Tom

[Twisties]

Thanks some more Mudman

 

Just rode it home from the dealer after service. I think it keeps trying to tell me it's name is "Flyer" , but aside from that:

 

I tried the procedure from the '06 thread, Set cruise control, then reset avg. speed on BC. Compared and found that at highway speed, I'm still only 4 to 5 mph slow, just like at 35 where the radar installation is.

 

Validated the procedure at one of the permanent radar installations, set cruise control at 40 and reset BC. BC and radar installation gave me a dead match at 36. Therefore I think I learned two things:

 

1. Apparently, since specs are quoted in both percent and an absolute mph figure, there is a scalable component to the error, and an absolute component, eg. error = m(speed) + b where m is a slope, and b is a y-intercept. On my bike m is small and b is large, about 4 to 5 mph, since the error did not scale with speed, which was my big concern.

 

2. The BC method works! No GPS needed. Seems like two people validated vs GPS in '06, and now we can add a radar validation. Three out of three is good enough for me.

 

Regards radar issues: I had worried about the larger vehicles getting read instead of little old me, but I've learned that this radar installation waits until you are right up close, and does respond to the bike, and then flashes blank before moving to the next vehicle, between that and on some runs having a pretty clear path behind me, I'm pretty confident I can tell when it's reading me.

 

As to the cosign error, hadn't thought of that, but I understand what you are saying. The setup is pretty close to the street, but there must be some error. Next time I'll try to line up on it as close as possible.

 

Regards the stop watches and mile markers idea, again thanks! I don't about there, but here the mile markers aren't exact. To use that method I go about 30 miles. That makes the relative error from the discrepancy in placement of the signs small. e.g. If the sign is placed in front of a bridge, instead of on it, maybe it was moved 528 feet up, so you would have 10% error between signs, however if you go 10 miles, and still have 528 feet of error, that's only 1% error. Since I don't know what the error is, and there is really error in the placement of both the starting and ending markers, I go further. I'm still assuming the average placement is correct, another thing I don't know for sure, maybe someone can comment on that. This procedure also minimizes stop watch error, same principal. Anyway, I haven't had a chance to try that yet on the new bike. But thanks again for the idea.

[bobanddianne]

We've got an '07 and have consistant readings of 78 when the speedo says 80, and 39 when the speedo says 40.

Both readings were from a GPS and from CHP speed displays up in northern california.

That's close enough for us