How inaccurate is your Buddy Speedometer & Odometer

rick71454 · Post by **rick71454** » Fri Sep 14, 2012 11:03 pm

Hello Buddyland:

How far off is your Buddy speedometer & odometer?

My 2009 Buddy 125 speedometer indicates 20% too fast.
I followed a friends recent model Honda car for a read comparing the car indicated speedometer reading and my Buddy. When the car was at 25MPH, my Buddy was indicating 30MPH. I dont have GPS, but I am assuming the car speedometer was more accurate than my Buddy speedometer.

I ride my Buddy 26 miles each way to work in a little town. My odometer indicates I went 28 miles.

Rick71454

JHScoot · Post by **JHScoot** » Fri Sep 14, 2012 11:05 pm

12.5%

exactly

persephonelily · Post by **persephonelily** » Sat Sep 15, 2012 2:12 pm

I don't know what percent it would be, but mine seems to be about 7 miles higher than I actually go. I have passed a couple of those speed check things and it's been about 7 on those, and the GPS on my phone says roughly the same.

buddy boy · Post by **buddy boy** » Sat Sep 15, 2012 4:31 pm

My speedometer is off by about 5 to 7 mph. I attach my Garmin GPS when I ride. I ride a lot of rural roads and highways. It makes for a nicer ride when no one is tailgating me because I'm going too slow.

Scooterboi · Post by **Scooterboi** » Tue Sep 18, 2012 6:48 pm

Speedo is 10% fast
55 bmph = 50 mph

Odo is spot on.

jaswol · Post by **jaswol** » Wed Sep 19, 2012 2:39 am

10 mph faster indicated than my gps. 60mph indicated = 50mph

Tocsik · Post by **Tocsik** » Wed Sep 19, 2012 3:20 am

For those of you that have checked your speedometer against a GPS (or radar), is the inaccuracy linear across the spectrum?
In other words, is the percentage difference less at lower speeds and more at higher speeds or is off by X% "across the board"?

JHScoot · Post by **JHScoot** » Wed Sep 19, 2012 9:55 pm

mine is across the board

Post by **ericalm** » Thu Sep 20, 2012 6:20 am

If the speedo is working correctly, it's off be a fairly consistent percentage. The odometer uses a different mechanism and is usually accurate despite speedometer optimism.

For more:
topic10818.html#139168

Robbie · Post by **Robbie** » Thu Sep 20, 2012 11:45 am

It helps you understand the variance if you know what is taking place within the speedo (known as a speedometer head or head unit)

A bit of history......all speedometers were cable driven, either from the wheel or the transmission output shaft of cars and trucks until around the early nineties.
Currently, there are a few motorcycles using electronic speed sensor technology with Honda's Gold Wing being one of them.
At that time, electronic speed sensors were employed that also read off of transmission output shaft turns......this information is sent to the computer and to the "to simplify" the speedometer.
The electronic pulse rate is sixty pulses per mile and the speedo uses a time/speed program to display speed and mileage......quite accurate but inaccuricies can be caused by different tire diameters.

The speedo on our scooters is cable driven off the front wheel and the universal 60 cable turns per mile is employed.
This is determined by tire diameter and the gearbox at the wheel.
Because the outer diameter of the tire can and often is different by brand, even though the sidewall dimensions (For example, a 100/90/10) are the same between brands, the wheel turns per mile can be more or less than enouph to turn the cable 60 times.
So, that will cause a mechanical inaccuracy of the odometer....within the speedo head there are gears turning the odometer drum.....every sixty turns will turn the tenth meter one full turn, it will turn the mile meter one digit and so on.
As most have found though, even though the indicated speed is off by a large percentage, the odometer is pretty darn close.

The reason the speed indicated is often incorrect is due to the way the needle is moved.
At the top of the speedo head, but below the face plate, the shaft that is geared to the odometer has a bar shaped magnet attached through the center of the bar.
Above that is a metal drum, attached to the upper frame of the speedo, still below the faceplate.
On top of the drum there is a shaft extending through the faceplate and this is what the speedo needle is pressed on to.
The drum has a light 'clockspring' that holds/returns it to a needle down position when not moving.

While driving, the cable spins the magnet, the drum surrounding the magnet begins to follow the rotation and the return clockspring resists that movement, creating a smooth needle movement.
So, thats the variable.....spring too tight, reads low, spring tension low, reads high.....needle incorrectly positioned on the shaft, reads whatever.

If one could take the faceplate off with a known, say ten percent varience, and get the needle off without breaking it, it would be possible to get it closer to accurate at reassembly.....maybe.

The membership here is comprised of many younger folks and you all are accustomed to the accuracy of electronics in everyday life.
I'm from the day of all vehicles using the same design, cable driven speedometers and no GPS so there was no way to know how far off they read.....unless you got 'Radared' that came with the ticket though.

But I do know that those vehicles read high back then as I had several radar adventures caused by a heavy foot.

I suspect that this was to cover all the manufacturers from hearing about the speedo causing the operator to get a ticket.

Happy reading,
Rob

Scooterboi · Post by **Scooterboi** » Thu Sep 20, 2012 1:37 pm

In the interest of futhering discussion on this topic . . .

Rather than reposition the needle (which is easily mangled) there are at least six other adjustment methods. Here are the ones I know of in order of increasing risk and hassle factor.

1) Demagnitize the unit (just slightly!)
http://www.ibmwr.org/ktech/speedo-cal3.shtml
Carefull! The only way to go back is order another speedo!

2) Pull the magnet out of the drum (just a little!) reducing the force applied to the spring. I thought about doing this and there is a paper online that explains exactly how at:
http://home.jtan.com/~joe/speedo.htm.
The only recovery problem I can see is that the speedo can only be "tapped" back and forth so many times until you break it.

The paper is also an excellent explaination of what is going on in there.

3) Print a new speedo card. IOW, don't move the needle, move the speed marks. The easiest way appears to be using MS Excell to graph a pie chart that will give you the size, curve and ratio to correct the problem. Print it on to some adhesive material that can stand getting a little wet and "viola". I never actually followed through designed the graph but I believe it wouldn't be that difficult. Might look a little clunky unless you are careful and position it just right. Getting the adhesive material could be a problem on the thin aluminum.

4) Change out the gear in the wheel to the correct ratio. This is the gear that changes the forward rotation of the front directly into cable rotations. Relatively easy to get to, but what would seem to be a simple one-gear "plug and play" is actually quite complicated because there are several thousand styles of those little gears. The good news is the process easily reversible. Bad news: unless you drive a vehicle that is very popular (Chevy Nova anyone) it is doubtfull you will find the exact match (or even close) that will work for you.

5) Order a speedometer "ratio adapter". Basically a little gear box that changes the cable rotation speed at the wheel gear head. The most promising one I could find is the "777 Ratio Adapter" at:
http://www.a1electric.com/speedometer.htm
but there are MANY variations including various angles of take off and attachment points. Not bad for ~$100, easy to install/uninstall, and most places are willing to work with you until it works.

6) Last, but not least, DO THE MATH! My speedo is 10% fast which is very easy to work with on the fly. 30 mph = 33 Bmph, 50 mph = 55 Bmph, etc. It may seem tedious if your variance is, say, 7% or 18% (yikes!) but this is not rocket science. There are only two or three mph speeds you need to know in Bmph to ride around in your neighborhood. Knowing those, you can interpolate and estimate accurately enough to not get a ticket and still make good time.

I hadn't considered the tire that much of a variable in the whole speedo calculations. I guess this means we should be giving our front tire make and model as well as the variance.

Michelin S1
Speedo is 10% fast
Odo is spot on.

Robbie · Post by **Robbie** » Thu Sep 20, 2012 2:04 pm

Nice follow up......

I am all in favor of option#6.......minimal brain damage.

Rob

Scooterboi · Post by **Scooterboi** » Thu Sep 20, 2012 2:38 pm

Correction:

In 2) the link doesn't work because I put a period at the end of the sentence. Cut and paste without the period and it works.

Rusty Shackleford · Post by **Rusty Shackleford** » Mon Oct 08, 2012 2:42 pm

Has anyone tried any of the methods mentioned to correct their speedometer? I was following my GF yesterday (she was riding her Buddy 125 and I was riding my CBR) and she said she hit 70bmph. I just had my speedo calibrated on a dyno and I was showing 60mph riding behind her. That's a pretty big error if she was reading right. I'm very much so interested in correcting this. That's too big to ignore. I just downloaded a GPS speedometer app for my phone that I'm going to use to record some max speed runs to get the closest % error over repeated runs.

rick71454 · Post by **rick71454** » Mon Oct 08, 2012 3:21 pm

Hello Buddyland; Rusty Shackleford:

I dont like my Buddy 125 speedo saying 60MPH when my actual speed is 50MPH. I followed my friends recent model Honda car and compared its speedo reading to mine. I assume the car speedo is accurate and I dont have GPS or a dyno for comparison.

According to scooterboi.............
I been doing his option 6 six, but I am think of doing option 3 three.
This is maybe tacky, but good enough for me.

Rick71454

Rusty Shackleford · Post by **Rusty Shackleford** » Wed Oct 10, 2012 12:03 am

I tried using a GPS speedometer app on my smartphone. It records the max speed, so theoretically, you can leave it in your pocket and try to maintain whatever pace down a stretch of road. What I found out was that it takes a couple of seconds for the speedometer app to calibrate as you change speed. This means there's a lag time that requires holding a steady speed to get a good reading. After a couple of runs, the % inaccuracy varied to widely for that to be considered a valid test.

I went out to Best Buy and bought an arm-band Android phone holder so I could read the GPS speedometer real-time against the one on the Buddy. This is what it looks like with my gear on. I'll be taking readings at 30mph, 40mph, 50mph, 60mph, and 70mph tomorrow and comparing the % error against each other along with a final average to try to and get a reliable number. Once I figure that out, I'll decide what direction to take as far as correcting it.

Rusty Shackleford · Post by **Rusty Shackleford** » Thu Oct 11, 2012 2:52 am

I did an extensive test run tonight and got some numbers. My Buddy 125's speedometer is 16.7% optimistic. Here's the data...

TEST RUN OBSERVATION (indicated mph / GPS mph / % difference)
35 -> 30 = 16.7%
47 -> 40 = 17.5%
55 -> 47 = 17.0%
58 -> 50 = 16.0%
64 -> 55 = 16.4%
70 -> 60 = 16.7%

Average % error = 16.7% ("% of" conversion = 85.7%)

CALCULATED CORRECTION (indicated mph / actual mph)
10 -> 09
20 -> 17
30 -> 26
40 -> 34
50 -> 43
60 -> 51
70 -> 60
80 -> 69

Now to call the scooter shop and see if they have any solutions to recommend. I doubt I'm the 1st person who's asked about it.

kmrcstintn · Post by **kmrcstintn** » Thu Oct 11, 2012 8:28 am

before I traded mine on a Stella, I ran it compared to the speed reading on my Garmin Nuvi 1300 gps...I was @ 17.5% inaccurate; example...my speedo was reading 40 and the GPS was reading 33; I repeated this 4 different times to confirm accuracy from run to run...same reading every time

Rusty Shackleford · Post by **Rusty Shackleford** » Thu Oct 11, 2012 3:26 pm

I just called the scooter shop here, and was told to check out... Modern Buddy!... to see what other people have done. Then they took my name and number to ask the mechanics and call me back. In all fairness, I suppose scooterists don't normally ride at speeds that warrant such scrutiny of speedometer accuracy, but it becomes worse as speed increases. Contrary to what anyone says, mechanically, speedo error will always be % based. At slow speeds, it's harder to accurately judge both because of speed and fluctuation there-of. The best way, logically to me, is to sustain as high of a speed as possible so that measurement will come from the most granular level of observation. This is why the highest speed I measured was exactly the same % error as the averaged % error over all, thus why I feel confident in claiming 16.7%.

For those of you who ride < an actual 40mph, this probably won't concern you much. My GF and I both have had the Buddy 125 at an actual 60mph... where the speedometer reads 70mph! For now, she has to go 5mph over if under 40mph, and 10mph over if over 40mph to stay in a reasonable range if there's other bikes following her. This level of error is ultimately unacceptable. Luckily, bikes are rear wheel drive and the speedo, in the case of the Buddy, reads from the front wheel. This means a larger tire is a feasible option... if a tall enough one will fit. Has anyone tried this? Not a wider tire. That won't fix anything. A taller tire. Has anyone fit a taller front tire on a Buddy?

Threads I've addressed this in for reference...
Biggest Tire...
spedometer inaccuracy...can it be fixed???
Buddy digital speedo? Way to make stock one more accurate?

CROSSBOLT · Post by **CROSSBOLT** » Thu Oct 11, 2012 3:44 pm

I have been told by The Man at Ozark Powersports that the "gearbox" on the front wheel can be tweeked since the gear on the wheel looks like a butterfly and the "wings" can be bent to change the ratio. I have had the box off the Buddy but I need to get some snap ring pliers to disassemble. Will advise.

Karl

CROSSBOLT · Post by **CROSSBOLT** » Mon Oct 15, 2012 4:17 pm

Got the snap ring pliers and there is NO adjustment: there are cut or rolled helical gear teeth of good quality just like it is supposed to be. There may be some chinese scoot that has what Tim described but not the Buddy. So live with the inaccuracy and convert in your head.

Karl

viney266 · Post by **viney266** » Mon Oct 15, 2012 11:06 pm

These things have speedos?

Oh wait !!! There it is...sorry, I was enjoying my ride too much to notice

Scooterboi · Post by **Scooterboi** » Tue Oct 16, 2012 1:12 pm

Rusty Shackleford wrote:" . . . I suppose scooterists don't normally ride at speeds that warrant such scrutiny of speedometer accuracy . . . Luckily, bikes are rear wheel drive and the speedo, in the case of the Buddy, reads from the front wheel. This means a larger tire is a feasible option... if a tall enough one will fit.

This is a common problem for motorcycles too! One of the papers I referenced is from a guy with a BMW motorcycle, pride of German engineering. http://home.jtan.com/~joe/speedo.htm

A little math can tell you how tall the tire would have to be to correct the problem. Just increase the distance traveled by 16.7%. 10" rims plus 3.5" tire = 13.5" radius or 42.4" cir.
42.4 x 1.167 = 49.5"
49.5" cir. = 15.7" radius and 15.7" - 10" = a 5.5" to 6" tire.

That's a REALLY tall tire and, if you could get it to fit, would almost certainly alter the handeling of your bike. Probably not for the better.

If you are dead set on fixing the problem, IMHO the easiest fix would be the in-line ratio adapter.

To quote myself:
"5) Order a speedometer "ratio adapter". Basically a little gear box that changes the cable rotation speed at the wheel gear head. The most promising one I could find is the "777 Ratio Adapter" at:
http://www.a1electric.com/speedometer.htm
but there are MANY variations including various angles of take off and attachment points. Not bad for ~$100, easy to install/uninstall, and most places are willing to work with you until it fixes the problem."

What I didn't mention is there are a TON of these speedo shops online, mostly in CA (go figure). It is likely that there is one that will be the perfect fix for this issue. I just happen to have an easy one to calculate in my head and so I looked no further. . . .

Scooterboi · Post by **Scooterboi** » Tue Oct 16, 2012 2:33 pm

My math is off but it still works out to a greater than 5" tire.

BuddyRaton · Post by **BuddyRaton** » Tue Oct 16, 2012 2:50 pm