Buddy MPH vs. Real MPH - Speed Trap!!!

sotied · Post by **sotied** » Mon Jun 09, 2008 5:35 pm

Just stopped next to a cop who was doing a speed trap in the next town. I wasn't speeding....LUCKILY.

So I went up to him and we chatted scooters and the Buddy for a moment. Then I asked if I could have him clock me so I could see how accurate my speedo was.

He said yes!

So he went a couple hundred yards away and I said I'd go at him at a constant (as constant as I could keep it) 30MPH.

Blasted at him and the speedo topped at 30 but was at 28/29 for most of my dash to him.

He said his radar read 24!!!

Is that normal? To have the Buddy MPH be off by 14+%?

AND, is it off by that amount all the way through the range or is it off by 5MPH everywhere?

I don't want my speedo to read 100 and have me just be doing 85. Or more realistically, I don't want cars riding up my butt when my speedo reads 50 and I'm really doing 43.

Thoughts?

jfrost2 · Post by **jfrost2** » Mon Jun 09, 2008 5:38 pm

Mine isnt that inaccurate, but it is normal to have it higher than you actually are going. I'll be reading 35mph while I am actually going 32-33mph. Similar around the top too.

UnionZac · Post by **UnionZac** » Mon Jun 09, 2008 5:41 pm

keep in mind that the radar gun may not have been perfectly guaged, especially at a lower speed. The same reason you're supposed to have about a 10mph window on the street and 5mph on the freeway with cops.

sotied · Post by **sotied** » Mon Jun 09, 2008 5:42 pm

So it's more like a set amount that the speedo is off rather than a percentage?

jrsjr · Post by **jrsjr** » Mon Jun 09, 2008 5:46 pm

sotied wrote:Is that normal? To have the Buddy MPH be off by 14+%?

Generally I figure on the speedo being 10% high. 14% is pretty high, but not shockingly so. My suggestion is have somebody pace you with a car and see what 60, 50, 40 & 30 on your speedo compare to. If you get a chance to do that, I'd be very interested to hear the results.

-John

sotied · Post by **sotied** » Mon Jun 09, 2008 6:37 pm

jrsjr wrote:
sotied wrote:Is that normal? To have the Buddy MPH be off by 14+%?
Generally I figure on the speedo being 10% high. 14% is pretty high, but not shockingly so. My suggestion is have somebody pace you with a car and see what 60, 50, 40 & 30 on your speedo compare to. If you get a chance to do that, I'd be very interested to hear the results.

-John

Will see if I can get my brother to pace me at all those speeds this afternoon. We have a stretch of road that should be good to do this.

I'll post results if I get this done today.

BadBrains · Post by **BadBrains** » Mon Jun 09, 2008 7:23 pm

Maybe the small size of the scooter also has something to do with it? I dunno...

Dooglas · Post by **Dooglas** » Mon Jun 09, 2008 7:28 pm

Our Buddy seems to consistently read 10-15% high when measured against a local radar controlled warning sign and against another vehicle. Our Vino, on the other hand, is pretty much spot on when checked the same way so the issue does not appear to be how radar reads a smaller target.

Piedmont · Post by **Piedmont** » Mon Jun 09, 2008 7:39 pm

Is it possible to get the speedo adjusted? It seems like it should be doable. I don't like having to calculate my speed as I ride.

pugbuddy · Post by **pugbuddy** » Mon Jun 09, 2008 8:36 pm

I typically figure I'm 5-6 mph lower than my Bud-O-Meter shows.

Remember: Buddy Speed = BS.

avogel · Post by **avogel** » Mon Jun 09, 2008 8:40 pm

I make sure and go at least 5 over the posted speed limit on my buddy speedo, I know it is about 7% to 10% under what it says.

jperkins · Post by **jperkins** » Mon Jun 09, 2008 10:25 pm

I have a GPS and 10 percent is about what I get on the buddy, even at the higer speeds.

sotied · Post by **sotied** » Mon Jun 09, 2008 10:27 pm

Silly me!!!!

GPS!!!

I'll grab it from the car and run out now.

Back later. Will post my findings.

scoots4me · Post by **scoots4me** » Mon Jun 09, 2008 10:33 pm

No wonder I got passed the other day! It was my first time being passed and the pickup truck seemed annoyed. I *thought* I was doing the 30mph speed limit...maybe I was really only doing 20? WHOOPS!

BuddyRaton · Post by **BuddyRaton** » Mon Jun 09, 2008 10:46 pm

Here is a quote from apost in another forum explaining why it is off for EVERY scooter and motorcycle.

The motorcycle tire is rounded in both directions - fore/aft and left/right. Because of this the rolling radius is constantly changing, depending on which part of the tire is in contact with the road at that time - the shoulder has a considerably shorter rolling radius compared to the crown. In addition, tires are sacrificial items and over time, wear across the tread, but differently and non-proportionally depending on rider, road and use. Tires also slightly INCREASE their rolling radius as speed of rotation increases and the g-force causes expansion, and at the same time DECREASE at the point of contact with the road due to loadpath pressures- the tire is NEVER round in use, more like a flattened oval.

Speedo accuracy is legislated. It is mandatory that a speedo never UNDER-reads. Therefore, in order to cater for `worst case` scenario - heavily worn tire on the shoulder of the heavily-worn tread, under-inflated at high speed and heavy load, the manufacturers build-in a margin over over-read. The reason the legislation DOESN'T stipulate a fixed, 100% accurate speedo reading is for this reading as the legislators understand what many here do not - operating a vehicle in a fluid environment with many different variables precludes the fitting of an entirely accurate device.

The issue of the pointlessness of the demand for an accurate speedo is something I am happy to leave to others to inflict on the forum. It will not happen, you cannot have it, there is no point in asking for it. GPS is also inaccurate as a speed-measurement device in the environment we operate in, and what would you ever need a precision speedo for anyway? You ride at the speed that is safe for the conditions, never, ever, EVER to the absolute and precise limit posted. Fixating on the speedo means you have less focus on what is going on in front of you and you will probably die at your completely accurate 30.000mph because you didn't see the car stop in front of you

Follow the link if you want to see how fired up people can get about it!
http://burgmanusa.com/forums/viewtopic. ... eter+error

It really comes down to

Why is my speedo off by 10%?

WHY RED IS RED!

sotied · Post by **sotied** » Mon Jun 09, 2008 11:15 pm

I was gone for about an hour and now it's anarchy!!

I took my GPS with me and trust that the satellites following me and my scoot got my RELATIVE speed correct.

Buddy is BRAND spankin' new - 123 miles now, got it last Wednesday.

Speedo reads 30, GPS says 26.1

Speedo reads 40, GPS says 35.2

Speedo reads 50, GPS says 44.3

Your speeds may vary with conditions, tire size, newness of your scoot and whichever message board you're signed onto. I posted this same info on the cheese-eater's int'l site and now I'm banned.

Drumwoulf · Post by **Drumwoulf** » Mon Jun 09, 2008 11:19 pm

sotied wrote:Just stopped next to a cop who was doing a speed trap in the next town. I wasn't speeding....LUCKILY.

So I went up to him and we chatted scooters and the Buddy for a moment. Then I asked if I could have him clock me so I could see how accurate my speedo was.

He said yes!

So he went a couple hundred yards away and I said I'd go at him at a constant (as constant as I could keep it) 30MPH.

Blasted at him and the speedo topped at 30 but was at 28/29 for most of my dash to him.

He said his radar read 24!!!

Is that normal? To have the Buddy MPH be off by 14+%?

AND, is it off by that amount all the way through the range or is it off by 5MPH everywhere?

I don't want my speedo to read 100 and have me just be doing 85. Or more realistically, I don't want cars riding up my butt when my speedo reads 50 and I'm really doing 43.

Thoughts?

EVERY scooter ridden in the USA has an overly optimistic speedo. My Honda 250 Reflex did, my Buddy 125 does, and so does my Vespa GT200! -And it doesn't matter what the speedo says, it's up to you to keep cars from "riding your butt," either by speeding up, or, if you can't, by pulling over and letting the AHole go by..!

awfulshot · Post by **awfulshot** » Mon Jun 09, 2008 11:23 pm

so the speedo is actually pretty accurate, but they just add +5mph so they don't accidentally break the law.

andgosun · Post by **andgosun** » Mon Jun 09, 2008 11:32 pm

I measured mine with a GPS, and it reads 10% high. @ 20 it is off 2 mph, @ 30 off 3mph, @ 40 off 4mph etc. Knowing the error it is very easy to compensate and be very close to the real speed, but that hasn't dampened my joy of riding my Buddy 125.

Post by **ericalm** » Tue Jun 10, 2008 1:38 am

The speedo is always off by a percentage. Think of it this way: When you're sitting still, does it read 5mph? Does it ever jump 5mph faster? The acceleration—and the speedo variance—is on a curve.

Most Buddys are around 12% off. There have been numerous threads in the past discussing this.

GPS is the most reliable way to gauge the difference.

jrsjr · Post by **jrsjr** » Tue Jun 10, 2008 2:37 am

sotied wrote: Speedo reads 30, GPS says 26.1

Speedo reads 40, GPS says 35.2

Speedo reads 50, GPS says 44.3

So, I punched your numbers into a spreadsheet and here are the error percentages:
Indicated - GPS -- % Error
30 ---------- 26.1 - 14.9
40 ---------- 35.2 - 13.6
50 ---------- 44.3 - 12.9
which vary from the 15% the police radar measured at 30 to about the 13%, which is close to what we expect, at 50. Hmm...

sotied · Post by **sotied** » Tue Jun 10, 2008 2:50 am

jrsjr wrote:
sotied wrote: Speedo reads 30, GPS says 26.1

Speedo reads 40, GPS says 35.2

Speedo reads 50, GPS says 44.3

So, I punched your numbers into a spreadsheet and here are the error percentages:
Indicated - GPS -- % Error
30 ---------- 26.1 - 14.9
40 ---------- 35.2 - 13.6
50 ---------- 44.3 - 12.9
which vary from the 15% the police radar measured at 30 to about the 13%, which is close to what we expect, at 50. Hmm...

Also, there's probably rider error in there. I wasn't on an empty road flying along with the GPS in one hand and the throttle in the other.

I was on a crowded road at around commuting time with the GPS in the holder while I tried to keep the scoot steady at one speed and then glance down to read it at the exact moment I crossed 30, 40 and 50.

It didn't help that the power went out in my town at about 5PM rendering the traffic lights useless and making people do even more courteous stuff than they usually do.

So I could have been off by 1-2MPH on the GPS reading for any of those as I scanned the roadway and then glanced down to the GPS.

sotied · Post by **sotied** » Tue Jun 10, 2008 2:58 am

So, I punched your numbers into a spreadsheet and here are the error percentages:
Indicated - GPS -- % Error
30 ---------- 26.1 - 14.9
40 ---------- 35.2 - 13.6
50 ---------- 44.3 - 12.9
which vary from the 15% the police radar measured at 30 to about the 13%, which is close to what we expect, at 50. Hmm...

I think some of the math might be off. Let's use the 50. If we double it and go to 100 and double the GPS speed and go to 88.6. I get 11.4 as the difference on a 100 scale.

Isn't that 11.4% or should I just ignore math and go back to my writing (which is my day job)?

Same for the 40 x 2.5 = 100. 35.2 x 2.5 = 88 ... therefore an even 12%

And 30 x 3.333333 = 100. 26.1 x 3.3333333 = 86.999999999 about 13.000000000001%

WAY better than those huge numbers you put up.

PHEW! My speedo is nearly accurate.

nearly = I don't win

BuddyRaton · Post by **BuddyRaton** » Tue Jun 10, 2008 3:12 am

Just accept that it is off and ride happy!

sotied · Post by **sotied** » Tue Jun 10, 2008 3:18 am

BuddyRaton wrote:Just accept that it is off and ride happy!

Am removing the speedo. Will post photos when complete.

Syd · Post by **Syd** » Tue Jun 10, 2008 4:45 am

Bear in mind that the speedo's accuracy is directly related to the variance from 89 Octane fuel being used.

Post by **ericalm** » Tue Jun 10, 2008 5:30 am

sotied wrote:
So, I punched your numbers into a spreadsheet and here are the error percentages:
Indicated - GPS -- % Error
30 ---------- 26.1 - 14.9
40 ---------- 35.2 - 13.6
50 ---------- 44.3 - 12.9
which vary from the 15% the police radar measured at 30 to about the 13%, which is close to what we expect, at 50. Hmm...
I think some of the math might be off. Let's use the 50. If we double it and go to 100 and double the GPS speed and go to 88.6. I get 11.4 as the difference on a 100 scale.

Isn't that 11.4% or should I just ignore math and go back to my writing (which is my day job)?

jrsjr is measuring the % variance between the two posted speeds. I see what you're thinking, but you're factoring the speed readings up so one is 100, then converting the difference to a percentage. But you're confusing your basis—100mph is not the same as 100% speed. If you double both, the % error stays the same.

jim_0068 · Post by **jim_0068** » Tue Jun 10, 2008 5:56 am

<--- Financial Analyst

Formula for finding % change:

New / Old - 1

So the poster who used the spreadsheet is correct.

jrsjr · Post by **jrsjr** » Tue Jun 10, 2008 5:56 am

To be clear, I'm calculating what I said, the speedo error in percent. The actual speed is not in error, it's the speedo that's wrong. Therefore, you do the math as follows:

100*(speedo speed- actual speed)/actual speed = speedo error in percent

for example, 100*(30 - 26.1)/26.1 = 14.9 % indicating that the speedo reads 14.9 percent higher than the actual speed.

sotied · Post by **sotied** » Tue Jun 10, 2008 11:20 am

SO you've proven two things here...

1 - that F+ I got in Trig during high school was also accurate

2 - that my career path as a writer was chosen correctly

Bonus points

1A - I often figure that everything should equal 100

2A - I am going to need a financial planner if I ever get as famous as JK Rowling.

Thanks!

StL_Stadtroller · Post by **StL_Stadtroller** » Tue Jun 10, 2008 2:50 pm

sotied wrote: Is that normal? To have the Buddy MPH be off by 14+%?

Mine's off by 18% !!

Drives me bonkers too. 5% or so I can live with... but nearly 20%.... that sux ballz.

jrsjr · Post by **jrsjr** » Tue Jun 10, 2008 8:33 pm

sotied wrote:SO you've proven two things here...

1 - that F+ I got in Trig during high school was also accurate

2 - that my career path as a writer was chosen correctly

Bonus points

1A - I often figure that everything should equal 100

2A - I am going to need a financial planner if I ever get as famous as JK Rowling.

Thanks!

Actually normalizing to 100% is a smart idea, but you have to be careful about your thinking. in this case, what you're normalizing to (dividing by) is the correct speed so that you end up with the error divided by actual. Then you multiply by 100 to express the result in percent.

And, sigh, maybe what we actually proved here is why is was a good thing that I dropped out of J school and went down the engineering career path, lo, those many years ago...

Welcome to Modern Buddy where the people who can write, do, and the people who can't, do, too.

-John

Post by **ericalm** » Tue Jun 10, 2008 11:05 pm

sotied wrote:2A - I am going to need a financial planner if I ever get as famous as JK Rowling.

I highly recommend getting one anyway.

jrsjr wrote:And, sigh, maybe what we actually proved here is why is was a good thing that I dropped out of J school and went down the engineering career path, lo, those many years ago...

Probably a good thing anyway. Journalism/publishing industries suck right now. Sigh. I need a job.

AmyNTX · Post by **AmyNTX** » Wed Jun 11, 2008 3:09 pm

Well, I went on my first real ride on busy streets! It was so fun! My husband went with me on his Harley and he stayed in front. I wanted to know my real MPH so we paid attention and then wentdown a street that has "your speed is ___" so I have figured out mine is off by 4 MPH all the time. So I just go 5 MPH over what it says.

Where I live you get a ticket for "keeping up with traffic" (just got one in my car for going 7 miles over the speed limit) they are really strict about going the speed limit..so now I'm sure aboout my speed:)

EP_scoot · Post by **EP_scoot** » Wed Jun 11, 2008 3:22 pm

I am just happy my speedometer is not as "accurate" as my fuel gauge

I just keep up with traffic. If I am alone I shoot for an indicated 5-10mph over the posted, listen to the engine noise and then base my speed on the engine noise so I don't take my eyes of the road.

iinigma7 · Post by **iinigma7** » Wed Jun 11, 2008 4:01 pm

Syd wrote:Bear in mind that the speedo's accuracy is directly related to the variance from 89 Octane fuel being used.

Agreed. I'd also add that it's also directly related to whether or not you wear ATGATT or have upgraded your horn to a Stebel.

madtolive · Post by **madtolive** » Wed Jun 11, 2008 5:18 pm

iinigma7 wrote:
Syd wrote:Bear in mind that the speedo's accuracy is directly related to the variance from 89 Octane fuel being used.
Agreed. I'd also add that it's also directly related to whether or not you wear ATGATT or have upgraded your horn to a Stebel.

and have monkey butt powder in your pants.

90MPG · Post by **90MPG** » Wed Jun 11, 2008 10:48 pm

Wanted to test this also, so I used a gps.

Buddy 41 MPH - GPS 35 MPH
Buddy 65 MPH - GPS 55.x MPH (didn't want to stare at the gps too long.)

MikieTaps · Post by **MikieTaps** » Wed Jun 11, 2008 11:01 pm

madtolive wrote:
iinigma7 wrote:
Syd wrote:Bear in mind that the speedo's accuracy is directly related to the variance from 89 Octane fuel being used.
Agreed. I'd also add that it's also directly related to whether or not you wear ATGATT or have upgraded your horn to a Stebel.
and have monkey butt powder in your pants.

dont forget about the windshield

Christy · Post by **Christy** » Wed Jun 11, 2008 11:38 pm

i just keep up with traffic. hardly ever look at the speedo. I know it's wrong, just like my gas gauge, and (rumor has it) my odometer too.

Modern Buddy

Buddy MPH vs. Real MPH - Speed Trap!!!

Buddy MPH vs. Real MPH - Speed Trap!!!

Re: Buddy MPH vs. Real MPH - Speed Trap!!!

Re: Buddy MPH vs. Real MPH - Speed Trap!!!

GPS

Re: Buddy MPH vs. Real MPH - Speed Trap!!!

Re: Buddy MPH vs. Real MPH - Speed Trap!!!

Teh Math

Re: Teh Math