Speedomoter accuracy

How accurate is our speedometer on the Swing? I can be cruising at an indicated 75 mph and am still being passed by everyone.

I am still amazed that this bike can carry my fat butt (275 lbs) that fast and still have plenty of throttle left.

RobinC wrote:

How accurate is our speedometer on the Swing? I can be cruising at an indicated 75 mph and am still being passed by everyone.

I am still amazed that this bike can carry my fat butt (275 lbs) that fast and still have plenty of throttle left.

If you are running the OEM size tires, consensus say 10%.

So 75 - 7.5 = 67.5 MPH.

honda_silver wrote:

RobinC wrote:

How accurate is our speedometer on the Swing? I can be cruising at an indicated 75 mph and am still being passed by everyone.

I am still amazed that this bike can carry my fat butt (275 lbs) that fast and still have plenty of throttle left.

If you are running the OEM size tires, consensus say 10%.

So 75 - 7.5 = 67.5 MPH.

Yes, according to my GPS that is what i found to be true on mine too.
Paul

Showing my ignorance here....does a GPS show the speed in realtime so you can use it as a speedometer?

If so, I might be interested. What kind and how much?

RobinC wrote:

Showing my ignorance here....does a GPS show the speed in realtime so you can use it as a speedometer?

A lot of GPS have the ability to show speed in realtime.

RobinC wrote:

If so, I might be interested. What kind and how much?

Depends on which GPS you choose.

The primary factors on choosing a GPS are cost, manufacturer water-proof, motorcycle friendly (gloved fingers), and features/options.

I am watching the reviews on the new Garmin Zumo 660 - full Bluetooth-2. American Motorcycle Association (AMA) has a 20% discount on Garmin select models ... just not sure if that includes the Zumo 660.

http://silverwing.org/cgi-bin/topic_show.pl?tid=461

Robin,

My SWing isn't quite 10% off. When I'm doing 75 indicated my gps is showing 70 mph; 80 indicated is 75 mph on gps and then at 90 indicated the gps is showing 83 mph. I'm also still amazed at the power of the SWing too. I'm 210 lbs plus whatever I'm wearing or carrying and it has no problem, either 1 up or 2 up. If you get a gps you should think of getting DennisB's gps mount. It works great.

RobinC wrote:

Showing my ignorance here....does a GPS show the speed in realtime so you can use it as a speedometer?

If so, I might be interested. What kind and how much?

My GPS updates aprox every 3 or 4 seconds, so it works pretty good as a speedometer.
Paul

So if our speedometers are off 5-10%, how about the odometer, which in turn would affect my MPG calculations.

RobinC wrote:

So if our speedometers are off 5-10%, how about the odometer, which in turn would affect my MPG calculations.

The odometer is accurate.
The manufacturer has chosen to make just the speedometer inaccurate.

The speedomoter on all Silverwings is off by 4 mph. You have to be indicating 69 to be true at 65.

4mph error at 70 seems about right. This might save you a ticket esp if the office is bored or needs quota.

I am intrigued:

How is it possible that a device working as a speedometer does be a constant (in this case) 4 miles per hour above the actual speed?

The '10%' rule works and, as far as I can judge using my GPS, is roughly what my speedometer does.

HI Mike, my speedo is 4 mph under.

MikeO wrote:

I am intrigued:
The '10%' rule works and, as far as I can judge using my GPS, is roughly what my speedometer does.

The three I've had have all been around 10% too.

Hello.
Anybody tried speedo-healer ?

http://www.healtech-electronics.com/products/sh/

Bob

A friend used a Speed Healer on his big Burgman some years ago.
He found it worked well.

My findings regarding the speedo on my Silverwings, using my GPS, is that in order to reach an actual speed of 30MPH, the speedo is reading 33MPH.
This difference increases pro rata as speed increases, so that at an actual speed of 70MPH, the speedo shows 77MPH or thereabouts.

Given the inevitable minor mechanical differences in individual vehicles, my experience may be different from those of other Silverwing riders.

The speed shown on a GPS is not real time but it is close. If you hold your speed steady for a short time you will see the speed just measured using a point to point calculation. It is likely to be more accurate than your speedometer since it is based on position and time (assuming straight line travel).

In that case, this whole discussion is a complete waste of time since I doubt anyone here has put his Silverwing on a properly calibrated rolling road or whatever it is to record a spot-on check of speed, setting aside that the rolling radius of tyres may be slightly different.

That my GPS can register that I'm exceeding the speed-limit, pointing to greater accuracy than the speedometer, means nothing, I suppose.

I have also tested my speedo with a GPS and it shows approximately 8% faster ( by design laws speedos can show up to 10% faster, but no slower here in Oz). Now I know how fast I ride and can avoid being caught for speeding. No need for additional gadgets or super precise measurements; just enjoying the ride!

I find your comment somewhat rude and offensive, MikeO. Not good for a Site Admin.

10% is the norm for the Silverwing.
I worked with speedohealer as the test Mule which is why they make one for the Silverwing.
The speedohealer did its job, but of course correcting the speedo made the ODOMETER inaccurate.
So I decided ODOMETER was more important and removed it.
Having a Speedometer that read low means when speed isn't important to me I stay closer to the speed limit, and when it is important, I am aware of how fast I'm really going.

Dan

How you find my post is your business.

I found yours something of a put-down and the last, pompous and arrogant - my business.

That I am a moderator does not preclude me from expressing myself as a member of the forum.
I have always made it clear when I'm acting in the capacity of a moderator.
When you've been around a little longer, you will find out for yourself.

The fact remains that to speculate on what is and isn't accurate is a complete waste of time if one is not going to define the Mean.

To most of us, the GPS is probably the most accurate readily available to most of us.

If it is discounted, what do you use as the Mean?

MikeO...
My original comment was simply a response to the question of whether the GPS speed indicator is a real time event and confirming of it being more accurate than the speedometer. It was not a put down and was not offered in a derogatory manner. I directed a comment to you because of the tone of your response. I am sorry to have wasted your time. Obviously you are offended. I am sorry for that also. My business.

Thank you, Derrill - understood, and I'm grateful for your explanation.

I hope you will accept this post in the same vein.

Best wishes.

MikeO...
No problem. Let me assure you that I find this forum an invaluable and time-saving resource!
I appreciate you and your associates for your work.
DW

My 2010 and my 2012 swings are accurate.

It's not really a big deal to fuss about. I do think you need to know that the speedomoter is off by about 4 mph. That is all. . .

If it is 4 mph throughout the speeds, then your scale is off. If it varies like a percentage. then your speedometer is inaccurate.

All I am saying is -- when I am showing 69 on my speedometer I am actually doing 65 mph. And yes it is "graduating scale"

I can't believe all these people saying the silver wing speedometer is off. I've had a 2010 and now a 2012 and checked several times and found both the GPS and speedometer are exactly the same. You need to let the GPS to catch up if your running at higher speeds is all. If you try to compare them by speeding up to like 75 and you look at the speedometer and it says 75 and the GPS will say like 69 most people will accept that and back off. If you reach 75 and maintain that for like 3-5 minutes you'll see the GPS catch up.

The GPS is basically measuring your position repeatedly, measuring how far you move over a certain period of time, then dividing that distance by the time it’s averaged over. Most of the consumer units do not take into account Doppler shift when making their calculations so they read low from actual SOG (Speed Over Ground).

If you’re stationary, sometimes the GPS will quite often give you a speed reading, and this is because the consumer units are only accurate usually +/- 3-5 meters.

If you can maintain a perfectly steady speed on flat ground (not changing altitude) for several minutes, even the consumer GPS units should be able to give you a fairly accurate reading. But by far the best way to verify speedometer accuracy is with radar. Here in Wisconsin they put up radar sets with a big display that shows your speed as you approach it, as a deterrent to speeding. I have found the Silver Wing's speedometer usually is within 2 mph of what those radar sets show and my Garmin GPS will be a few mph below that.

Always keep in mind that point to point measurements used by consumer GPS units have a position accuracy of +/- 10%. There is no way they can display instaneous speed with better accuracy than their point measurement accuracy, except by averaging many, many points over time. So the GPS is most useful to calculate average speed point to point over great distances. Not so great for instantaneous speed measurements.

Most motorcycle speedometers are off by 5-10% at a 100kph. At least all the bikes I've had and everyone I've talked to. If you say your Silverwing is accurate at a 100kph then it must be broken .

Surely there must be an inaccuracy at some point, simply because tyres wear throughout their life.

It is generally accepted over here that manufacturers build in an over-reading to protect the motorist in the presence of Speed Cameras and themselves so they can't be held responsible for motorists being caught and saying: 'The speedo said I was doing XYZ MPH in an XYZ MPH zone so it's not my fault if I was exceeding the limit.'

MikeO wrote:

Surely there must be an inaccuracy at some point, simply because tyres wear throughout their life.

Actually, MikeO, it is quite minor. Most new motorcycle tires start out new with a tread depth of .250-.260" They are legally worn out at .094" tread depth.

Considering that the circumference of the average motorcycle tire is about 72" new, going from new tires to the legal maximum wear results in a change of 12 revolutions per mile, or about 1.3%. Which at 60 mph is a change in needle reading of .78 mph.

Another thing I'd like to mention for Silver Wing buffs is that at freeway speeds your rear has up to 1.5% slippage as compared to the front, and is the reason your rear tire always wears out at lower miles. Unlike most motorcycles, which take their speedo reading off the front tire, the Silver Wing takes it off the sensor on the rear end. So any speed error that exists in the calibration of the unit is made worse by the amount of tire slippage at high power input at high speeds.

The amount of slippage is dependent on the contact patch of the rear tire, which is smaller with a smaller diameter tire than it is with a larger one. The 1.5% quoted is the usual assumption for full-sized motorcycles. So it may be actually more than that with the Silver Wing.