[USSENTERNCC1701E]

Instructions in post #37

BLUF: 6.7% Speedometer overread on 2016 GSX-S1000F, US model.

Not yet familiar enough with the forum to know if this is the best place for it, if not, sorry.

I'm planning to install a Speedohealer. I don't like speeding for my commute, but here in Utah, it's dangerous to drive below the speedlimit, especially on a sportbike; seems to be people expect you to be speeding and if you're not, don't expect even a modicum of respect for your personal safety. Friday I got passed (on a four lane road mind you, with me in the right track of the right lane) so close I could have reached out and touched the car. And in my experience here, even if there's a cager near by going faster, it's the biker that'll get pulled over. So, I'd like to be able to know how fast I'm actually going.

For now, I'm calculating the percent error. I took my phone and a GPS logging app for a ride, about 20 minutes sustained at 60 MPH indicated. I trimmed off the initial acceleration and deceleration data, then deleted obvious outliers with data in chronological order. Next I reordered the data ascending with measured speed. I used a linear fit, and trimmed the leading and trailing data until the R-squared value was over 0.99 I then switched back to chronological and the linear fit had a slope of .0001 I considered this sufficient. All told I had 832 remaining data points for 20 minutes at sustained speed. My standard deviation is 0.44 MPH, given the speedometer readout is to the nearest whole MPH, this is within the instrument error. I got 55.97MPH actual for 60 indicated, a 6.71% overread, calculated by ( actual/indicated – 1 ) x 100

For 75 indicated, after analysis, got 70.00 actual, standard deviation 0.34, slope of linear fit for chronological order -0.00005, R-squared for linear fit on ascending order 0.9948, but only 437 data points and 12 minutes. Total overread, 6.67%. So still rounds to 6.7%, and the speedohealer only increments by 0.1%.

I got a handle bar mount for my phone, and put the GPS app in speedometer mode. With 6.7%, some speeds I took a look at, expected Actual/Indicated: 14.00/15; 27.99/30; 41.99/45. It's hard to hold this bike at 15MPH, but the other two checked out just fine, rounded to the nearest whole. Further, drove past a speed limit sign with integrated radar and readout, sign said 28, bike said 30.

Overall, seems the speedometer error is linear, 6.7%. I've got a speedohealer in the mail, should show up today. I haven't been able to find anyone claiming for certain that the bike does/doesn't have a speed sensor independent of the wheel tone rings. I'll be doing some wrenching around looking, barring that, I also have an FSM on the way. Hopefully there is a way to patch it in without potentially impacting ABS/TC. Granted, this is the first bike I've ever had with them, and I've been riding in cold rain through a canyon to work for the last week without either system activating (TC at 3) so I'm not convinced they're necessary, but I'm not too keen on degrading even unnecessary safety features.

-Jaren

P.S. Excle spreadsheets with analysis

https://drive.google.com/file/d/0BxxoMzdrnYyjblZmZGNEZjlqV2s/view?usp=drivesdk
https://drive.google.com/file/d/0BxxoMzdrnYyjLTMyTjl6UWlMeU0/view?usp=drivesdk

 

[blueglue]

I just changed my tyre from a 50 to a 55. seemed less of a headache

 

[USSENTERNCC1701E]

I just changed my tyre from a 50 to a 55. seemed less of a headache

Both, or just rear? (Edit: well, I guess the 50 to 55 would have to be rear only, but did you also change ratio on the front?) Did it impact TC at all (ABS if you have it)?

Side note, that only comes to about a 1.8% correction. Though it'd get it close enough to a 5% error I could do the rest of the correction in my head.

I'm thinking what I may wind up doing, if the only sppeed sensors are the tone rings, is use one of the speedohealer settings at -6.7%, and the other at 0, switching to 0 for inclement weather (where driving a tad slow certainly wouldn't be a bad thing anyway). I'm also wondering if this would make TC and ABS more sensitive, guess that depends on what the tolerance between wheelspeeeds defining slip is.

 

[JeffroGymnast]

Changing to a 55 rear tire should (theoretically) increase circumference by 3.1%.

Tire circumference (in.) = rim_diameter + [(2 x aspect_ratio x section_width)/25.4 mm/in ]

a 190x50x17 is theoretically 24.48"
a 190x55x17 is theoretically 25.23"

circumference increase would then be new circumference / old circumference - 1
= .0306 or about 3.1%

Of course, each brand or model of tire will have a slightly different geometry anyways. Take a look at the 55 rear tire thread; plenty of people have put a 55 on and had no issues with ABS/TC.

 

[Beaker]

I've put a 55 on too. Don't really care about all the math. My sat Nav can work it out quite nicely. And it can compensate for tread wear, pressure difference and changeable weather.



Sent from my iPhone using Tapatalk

 

[USSENTERNCC1701E]

Changing to a 55 rear tire should (theoretically) increase circumference by 3.1%.

You're absolutely right, I forgot to double the tire profile.

-Jaren

 

[mattnz]

Changing to a 55 rear tire should (theoretically) increase circumference by 3.1%.

Tire circumference (in.) = rim_diameter + [(2 x aspect_ratio x section_width)/25.4 mm/in ]

a 190x50x17 is theoretically 24.48"
a 190x55x17 is theoretically 25.23"

circumference increase would then be new circumference / old circumference - 1
= .0306 or about 3.1%

Yep. With a 55 on my speedo now reads 103 instead of 100 at same gear and revs.

 

[rcannon409]

If you really think about it......

Now look, we live in a society where your car must beep until you snap your seat belt in place..

We MUST have signs saying "EXIT" on doors that never close.

With that in mind, can you imagine the outrage, and the legal bill when I claim my new Suzuki caused me to speed. It is defective because when I replaced a tire, it was found the speedometer showed 75 and I was really doing 80.

I'll bet this is why. What make sit even more likely is that the odometer is typically much closer. I fit were off the 6.7%, the 12,000 mile warranty would really mean 12,700....

 

[USSENTERNCC1701E]

With that in mind, can you imagine the outrage, and the legal bill when I claim my new Suzuki caused me to speed. It is defective because when I replaced a tire, it was found the speedometer showed 75 and I was really doing 80.

This is exactly why. I remember reading an article, I think it was in Motorcycle Consumer News, about the speedo error, and it is to prevent lawsuits for "vehicle exceeding performance expectations." Which makes no **** sense to me, but whatever.

 

[USSENTERNCC1701E]

Putting the bike on a maintenance stand and running the rear wheel gives no speedometer reading. I did not have a stand available to lift the front, so I disconnected the sensor and ran it by hand across the tone ring. I got a reading, indicating the speedometer reading is dependent only upon the front wheel sensor.

https://youtu.be/jtVa3qBkR7k

Now to track down the wire to somewhere convenient, patch in the speedohealer, and test it all out.

-Jaren

 

[JeffroGymnast]

Seems we have some conflicting data here.

If the bike determines the speedometer value solely from the front wheel, changing the rear tire shouldn't affect the speedo at all...

mattnz is reporting otherwise, though.

Perhaps the ABS unit determines speed from both wheels, unless it decides one of them is irrational (ie, rear wheel speed = 0, front wheel speed = 2 mph... it makes sense that the actual speed is at least 2 mph since the front wheel speed can only be equal to or less than the actual bike speed).

 

[USSENTERNCC1701E]

Very well could be. I admit, I'm getting a little nervous, working on the install now, and the universal kit is set up for a three wire sensor, this has only two...

 

[USSENTERNCC1701E]

Okay, well, I have confirmed that Speedohealer does not work with the GSX-S1000F ABS. And nearly had myself a heart attack. Had the ignition on so I could check speed indications, I suddenly hear this ticking which slowed down until it stopped. Tried to start it, no go. Thought I'd fried the ECU or something. Battery died, headlights were on bright, sound was fuel pump. So, I no longer have the motivation to pursue the front vs rear question.

 

[slothman]

just follow the flow of traffic, if you are that worried about speed

 

[JeffroGymnast]

Yikes! Well, I think for now we will have to calculate real speed in our heads... Once the GSX-S ECU is "cracked" and can be played with, I'm sure it won't be hard to change the conversion factor for the speedo.

 

[USSENTERNCC1701E]

Yikes! Well, I think for now we will have to calculate real speed in our heads... Once the GSX-S ECU is "cracked" and can be played with, I'm sure it won't be hard to change the conversion factor for the speedo.

Yarp. Well, at least for the US and stock tire folk, an easy rule emerged, actual is 1MPH less for every 15MPH indicated.

 

[USSENTERNCC1701E]

just follow the flow of traffic, if you are that worried about speed

True, but now that I know I can't fix it, it's actually bothering me on a whole 'nother level... it's like, damnit Suzuki, it's my bike, let me see the real speed if I want to. Same reason I root all my phones, basically.

-Jaren

 

[mattnz]

Seems we have some conflicting data here.

If the bike determines the speedometer value solely from the front wheel, changing the rear tire shouldn't affect the speedo at all...

mattnz is reporting otherwise, though.

Perhaps the ABS unit determines speed from both wheels, unless it decides one of them is irrational (ie, rear wheel speed = 0, front wheel speed = 2 mph... it makes sense that the actual speed is at least 2 mph since the front wheel speed can only be equal to or less than the actual bike speed).

If the rear wheel with a 55 tyre on it is turning 3% 'more' at the same revs and increasing the speed of travel then the front must be turning faster too.
Could still be reading the speed off the front wheel only.

 

[JeffroGymnast]

If the rear wheel with a 55 tyre on it is turning 3% 'more' at the same revs and increasing the speed of travel then the front must be turning faster too.
Could still be reading the speed off the front wheel only.

My GSX-S hits an indicated 86 MPH at 6000 RPM.

If I were to change my rear tire to a 55 (~3.1% bigger circumference), I'd be at ~5820 RPM (6000 / 1.031). However, my front tire has not changed at all, and would still be rotating at the exact same rate as before. So if the speedo only reads speed from the front wheel (pulses of the ABS ring per second), it would still read 86 MPH.

 

[nicka]

I am surprised someone hasn't done this and even able to make some money out if as it is an easy fix for some one motivated to do it. I actually spoke to the right person just the other day but I haven't taken it any further as I said some one with the motivation , who I spoke to is an electrical genius and also a laser cutter and he agreed it will work
but I will have to remove my wheels and take the sensor disc to him and he can redraw the disc in autocad with more holes with equal spacing and slightly smaller holes so it's even and have this cut out with a laser cutter then the speedo will read less, I'm not sure how many holes more but it would be an easy calculation , I'm guessing about 2 holes, replace both discs front and rear and everything will still work and the speedo will be corrected