I wanted to see if the spedometer on my Buddy 125 was the 'usual' 10% optimistic so I ran it and compared it to the speed reading on my Garmin Nuvi 1300 gps...the results have me a bit upset
I did 4 different runs and each time when my scooter spedometer indicated 40 mph the reading on my gps was 33 mph, which indicates a 17.5% inaccuracy!!!
is there anything that can be done to fix this??? can the spedometer be recalibrated by my dealer? is this considered a faulty unit that needs replacement under warranty???
this also indicates that performance is lacking in general since I cannot even reach 55 mph on a flat road going WOT!!!
"When your mouth is yapping your arms stop flapping, get to work" - a quote from my father R.I.P..
always start with the simple, it may end up costing you little to nothing
And this also contains a post by LMC with touring links. Somehow I never noticed this before. There are a few new finds for me here. Thanks for indirectly steering me here.
Rob
"Sponges grow in the ocean. That just kills me. I wonder how much deeper the ocean would be if that didn't happen."
- Steven Wright
I'm wondering if there might also be a small percentage variation between the 150's/170i's and the 125's because the 125 comes with 3.5x10 stock tires and the 150's/170's come with 100/90 tires. I know there's only a very small difference between those tires, but on this small of a scale, that might be enough to cause a larger percentage variation on the speedo. I'm planning to put 100/90's on my 125 when the time comes since they're a bit wider.
Its not just limited to Genuine buddy. I have a Yamaha that reads 69 MPH at an actual 55. I just painted a small red line on the speedo face at 69. That is the only one that mattered.
Speed is only a matter of money...How fast do you want to go?
pdxrita wrote:I'm wondering if there might also be a small percentage variation between the 150's/170i's and the 125's because the 125 comes with 3.5x10 stock tires and the 150's/170's come with 100/90 tires. I know there's only a very small difference between those tires, but on this small of a scale, that might be enough to cause a larger percentage variation on the speedo. I'm planning to put 100/90's on my 125 when the time comes since they're a bit wider.
This is true. My mpg's went down when I switched from 3.5 - 10 to 100/90 - 10, but I knew it was due to the larger tire diameter affecting the speedo. I haven't done a GPS mileage comparison against the speedo yet. But I will. Unfortunately, I never took detailed measurements with the 3.5 - 10's, so I won't be able to precisely compare how it affected the speedo from one tire size to the other.
Capt_Don wrote:There is no direct law that mandates this. Only pressure on the companies can effect change.
In fact, there is legal pressure for them to keep the reading high. If the speedo consistently says you're going faster than you really are, you can't sue them when you get a speeding ticket, or when you get in an accident from going too fast, or anything of that sort. It's impossible to make it 100% accurate (as demonstrated by the variation from changing tires), so they make sure it's always at least a little too high.
Capt_Don wrote:There is no direct law that mandates this. Only pressure on the companies can effect change.
In fact, there is legal pressure for them to keep the reading high. If the speedo consistently says you're going faster than you really are, you can't sue them when you get a speeding ticket, or when you get in an accident from going too fast, or anything of that sort. It's impossible to make it 100% accurate (as demonstrated by the variation from changing tires), so they make sure it's always at least a little too high.
Why wouldn't the auto industry be subject to the same legal pressures?
Rob
"Sponges grow in the ocean. That just kills me. I wonder how much deeper the ocean would be if that didn't happen."
- Steven Wright
Capt_Don wrote:There is no direct law that mandates this. Only pressure on the companies can effect change.
In fact, there is legal pressure for them to keep the reading high. If the speedo consistently says you're going faster than you really are, you can't sue them when you get a speeding ticket, or when you get in an accident from going too fast, or anything of that sort. It's impossible to make it 100% accurate (as demonstrated by the variation from changing tires), so they make sure it's always at least a little too high.
That makes no sense. Not in that that is a reson given, but in a practice application. From reading on the issue, I see it as a throw-back to a bygone era, just like the red 55. It is legally on the driver to maintain the proper speed and matience of all parts. So a consumer driven push to install reliable speedometers does not tread on any currently active law. I know lots of bike riders that have damn near dead on meters. Consumer pressure can be as compelling as legal pressure when there is no direct law involved.
For anyone curious, I did a speedometer comparison the other day with my GPS. I have a Buddy 125 with 100/90 - 10 Heidenau K61's instead of the stock 3.5 x 10 Cheng Shin's. That means my new tires have a slightly larger diameter than my old tires. So my speeds 'should be' less optimistic (closer to true speed). The spread would likely be larger with the stock tires (further from true speed).
The first number is the Buddy speedometer reading. The second number is the actual mph according to my Tom Tom GPS.
k1dude wrote:For anyone curious, I did a speedometer comparison the other day with my GPS. I have a Buddy 125 with 100/90 - 10 Heidenau K61's instead of the stock 3.5 x 10 Cheng Shin's. That means my new tires have a slightly larger diameter than my old tires. So my speeds 'should be' less optimistic (closer to true speed). The spread would likely be larger with the stock tires (further from true speed).
The first number is the Buddy speedometer reading. The second number is the actual mph according to my Tom Tom GPS.
That's pretty much identical my not so scientific, non-gps BMPH to MPH comparison. I came up with a BMPH to MPH curve that starts at a 10% difference at low speeds increasing to 15% difference at top speeds. As I have no GPS I've just made use of those "your speed is" signs that the LAPD like to place around town and then compare my speedo to what their radar tells me. (I have Heidenau K61's too).
Skootz Kabootz wrote:That's pretty much identical my not so scientific, non-gps BMPH to MPH comparison. I came up with a BMPH to MPH curve that starts at a 10% difference at low speeds increasing to 15% difference at top speeds. As I have no GPS I've just made use of those "your speed is" signs that the LAPD like to place around town and then compare my speedo to what their radar tells me. (I have Heidenau K61's too).
Mine's basically a linear 14% difference. I wish I had done the same test before I got rid of the stock tires. Next I need to determine the accuracy as far as the odometer is concerned to see if it corresponds to the speedometer error.
When you lean into a turn you are using a smaller diameter contact patch on your tire. That is why they read high while riding upright, so they will not indicate a speed lower than you are going when leaned over. This is true of almost any PTW vehicle.
Yeah they could put a fancy speedo that would compensate etc etc....and then have to kick the price up another few hundred bucks.
This has come up alot lately. It seems new riders are REAL upset about a simple spedo discrepancy. From my experience, EVERY bike's spedo is off. My father's 2005 BMW was actually more inaccurate than my '80 Vespa P200e was. Every bike I've owned from a Honda CB200T to the Harley Davidson Sportster I was riding for nearly a year before getting back into scooters was off by some degree. It's just the way the bikes are.
Besides, I rarely pay attention to the spedo. Go fast enough to not get run over, but slow enough to not run into the guy in front of you. Avoid speed cameras and you're good.
I understand the frustration and the reality. I have been a rider since way back before the turn of the century, and it has not bothered me till now. Maybe because I knew that no matter how fast I wanted to go my Targa and Arrow would only get around 30... You know, this is the future, we have flying cars now, why can't we have an inexpensive accurate... oh wait, never-mind!
Rob wrote:Why wouldn't the auto industry be subject to the same legal pressures?
If it were as difficult to make an accurate speedometer for a 4-wheel vehicle, they might be.
Ah, I drew the conclusion from previous discussions on this subject that the inaccuracy was more intentional than inherent.
What I still don't understand is the nonlinear results of many of these speedo/GPS tests. I rode the 750 today and it "tested" as basically 5% optimistic across the range (up to 75 mph). I'll do the same on the 1500 tomorrow and check that out.
Rob
"Sponges grow in the ocean. That just kills me. I wonder how much deeper the ocean would be if that didn't happen."
- Steven Wright
SYMbionic Duo wrote:the difference between 3.5 x10 and 100/90 x10 is miniscule. <7mm in rolling distance. which is 0.5% difference.
Unless you are performing surgery or engaging in rocket science. Don't worry about it.
THANK YOU!!!
It's just a speedometer. If you are THAT worried about obeying the law to the last decimal point, you really need to learn to live a little. Lives don't hang in the balance of the spedo being 4 mph off.
BuddyRaton wrote:When you lean into a turn you are using a smaller diameter contact patch on your tire. That is why they read high while riding upright, so they will not indicate a speed lower than you are going when leaned over. This is true of almost any PTW vehicle.
Yeah they could put a fancy speedo that would compensate etc etc....and then have to kick the price up another few hundred bucks.
I have read this explanation everywhere from Practical Motorcycling to here and MV. I understand the geometry behind it. What I don't understand is why no real-life numbers are ever given to support this explanation. For that reason alone, I call BS.
I wonder if a manufacturer has ever timed their product running in circles of varying radius to determine what lean angle to use as the zero point - the effective tire diameter at which the speedo is correct. Why not make the speedo close when riding essentially straight ahead, the direction of 95% of travel? I'd wager the difference of tire radius in minor turns is trivial.
Really, if you are riding the twisties, and paying attention to your speedo to ensure you don't speed, a ticket should be the least of your worries - you're either going to miss the corner and run off the cliff or get run over!
SYMbionic Duo wrote:the difference between 3.5 x10 and 100/90 x10 is miniscule. <7mm in rolling distance. which is 0.5% difference.
Unless you are performing surgery or engaging in rocket science. Don't worry about it.
Not necessarily. Someone a few years ago lined up a whole bunch of 3.5 x 10's and 100/90 - 10's side by side - different brands and models. He did it to illustrate that the listed size doesn't reflect reality. Some 3.5's were taller than the other 3.5's and even taller than the 100/90's. I think one of the 100/90's was smaller than all the 3.5's.
I know this is also true for mountain bike tires. The listed size is almost meaningless. It's such a problem that there are websites that list actual sizes versus listed so people can properly choose their next tire without guessing and hoping.
I know that the Heidenau K61's in 100/90 - 10 are noticeably much larger in diameter and width than the Cheng Shin's in 3.5 x 10 that they replaced. The loss of clearance against my fenders is obvious too.
Syd wrote:I understand the geometry behind it. What I don't understand is why no real-life numbers are ever given to support this explanation. For that reason alone, I call BS.
[..] Why not make the speedo close when riding essentially straight ahead, the direction of 95% of travel? I'd wager the difference of tire radius in minor turns is trivial.
Really, if you are riding the twisties, and paying attention to your speedo to ensure you don't speed, a ticket should be the least of your worries - you're either going to miss the corner and run off the cliff or get run over!
Yes! If I'm riding in a relatively straight path, a 10-20% optimistic speedo such as people in this forum have reported is nuts.
BuddyRaton wrote:When you lean into a turn you are using a smaller diameter contact patch on your tire. That is why they read high while riding upright, so they will not indicate a speed lower than you are going when leaned over. This is true of almost any PTW vehicle.
Yeah they could put a fancy speedo that would compensate etc etc....and then have to kick the price up another few hundred bucks.
I have read this explanation everywhere from Practical Motorcycling to here and MV. I understand the geometry behind it. What I don't understand is why no real-life numbers are ever given to support this explanation. For that reason alone, I call BS.!
BuddyRaton wrote:When you lean into a turn you are using a smaller diameter contact patch on your tire. That is why they read high while riding upright, so they will not indicate a speed lower than you are going when leaned over. This is true of almost any PTW vehicle.
Yeah they could put a fancy speedo that would compensate etc etc....and then have to kick the price up another few hundred bucks.
I have read this explanation everywhere from Practical Motorcycling to here and MV. I understand the geometry behind it. What I don't understand is why no real-life numbers are ever given to support this explanation. For that reason alone, I call BS.!
10th grade geometry should help you out.
C=Pi D
Cute, (and it's Pi*D) but goes no further in answering my question than every other post I have read. Give me some real world numbers.
I rarely look at the speedo, I just keep with the flow of traffic. When riding alone I go with what feels good. If and when leading a ride... then I pay attention to the speedometer.
The more I think about it the more I am convenience that all that needs to be done is to produce the correct graphic for each model, and to base it on stock wheel size. I am glad that everyone who does not care is fine with it, but I would like my readings to be truthful.
Syd wrote:Why not make the speedo close when riding essentially straight ahead, the direction of 95% of travel? I'd wager the difference of tire radius in minor turns is trivial.
^ This ^
There's no reason whatsoever to have an intentionally built in conservative error of 10% to 20%. Keeping MC riders guessing is more of a danger than a benefit as far as safety is concerned. 5% I could understand. One of the manufacturers needs to break the mold.
Syd wrote:Why not make the speedo close when riding essentially straight ahead, the direction of 95% of travel? I'd wager the difference of tire radius in minor turns is trivial.
^ This ^
There's no reason whatsoever to have an intentionally built in conservative error of 10% to 20%. Keeping MC riders guessing is more of a danger than a benefit as far as safety is concerned. 5% I could understand. One of the manufacturers needs to break the mold.
I'd be surprised if that's not how they're calibrated. The issue isn't solely due to tire size and curvature, though. That conspires with the eddy current speedo unit.
If you guys are really concerned, why not create an adhesive overlay (or simply masking tape it if you don't want to get fancy)?
The reasons the OEMs don't do this? First, there are many variables affecting the deviation. Second, they cannot allow a speedo to read under actual MPH, or they'll be in hot water.
Eric // LA Scooter Meetup Group // Stella 4T // Vespa LX // Vespa LXS // Honda Helix // some, uh, projects…
Capt_Don wrote:There is no direct law that mandates this. Only pressure on the companies can effect change.
In fact, there is legal pressure for them to keep the reading high. If the speedo consistently says you're going faster than you really are, you can't sue them when you get a speeding ticket, or when you get in an accident from going too fast, or anything of that sort. It's impossible to make it 100% accurate (as demonstrated by the variation from changing tires), so they make sure it's always at least a little too high.
Why wouldn't the auto industry be subject to the same legal pressures?
Rob
They are in Germany which I'm told is why my BMW 348i has an optimistic speedometer on it though it isn't quite as off as on the scoot.
Good solid data. Better yet that this shows good a verified comparison.
With an approximate 10% in-accuracy (mine) it's not too difficult to do the math on the fly in your head.
Aging is mandatory, growing up is optional.
My kids call me 'crazy', I prefer 'Eccentric'.
Nullius in verba
dont know if it's thier devices or the speed sensor.
most measure speed from a drive shaft or a axel or wheel. could be the pickup or the display is cheap.
find the pickup and try swaping it for another scooter or motorcycle pickup.
