I was out for a ride last weekend on my ZX-6R with a buddy on his GSXR600. When we got back I said 'Man we were doing 94 mph on the freeway back there'. He replied, 'No we weren't, more like 84 mph'. OK, so that got me to thinking, 'How far off are the speedometers on my various bikes'? So I download a GPS speed app for my iPhone 4S and checked it against my Ford Explorer, dead on at 70 mph. So I set it to record maximum speed and stuck it in my jacket pocket and went for a ride on my ZX-10R and CBR1000RR, both were dead on at 96 mph on GPS and speedometers. Cool, I'm thinking, so I do the same with my ZX-14. I find a nice straight section of backroad and take it up to 120 mph and then pull over and check the max speed recorded on the GPS, 95 mph. 25 mph off, 'that can't be right' I'm thinking so I try it again, this time 110 mph indicated and it reads a whopping 89 mph, 21 mph off. What a let down, this bike is nowhere near as quick as I thought. Anyone else tried a GPS to check their speedo error?

Never tried a GPS but noticed a big dif after changing to a 190/55 tire which should correct the speedo. Suddenly, My speedo makes sense compared to the cars on the expressway that normally do about 60 mph. I believe the stock speedo reading is about 8% fast with a 190/50 and that gets worse as the tire wears and even worse if you do over 60 mph. Your speedo/GPS discrepancy is right on target, 8% fast.

Get a SpeedoHeeler SH-v4. Works like a charm. Warning--had water problem with the piggies on that thing one time. Garden hose baths NOT recommended.

I have multiple bikes and they all have some amount of speedo error.

It's impossible to keep track of which one is off by how much at which speeds, etc. So I run a Garmin GPS on all my bikes, and never look at the bikes speedo anymore - I just take the reading off of the GPS.

Added bonus is that it saves the top speed attained, until you clear it out for the next run

My 14R is 3 mph fast at 70 and 85. This maakes sense because I drive and ride the same way and same speeds to work. If my bike says 70, cars are keeping up with me. In my truck 70 I'm passing people. 73 on my bike is the same as 70 in my truck. I know from tickets my truck is +- 1 mph.

Gen 2s have far less speedo error than Gen 1s and a lot of other bikes. I've heard it's basically 3 mph all the way up to 190 mph... this relaly makes sense since the bike will do an actual 186 mph.

As far as your GPS... I doubt your bike is that off. Think about this. YOu know x rpm in y gear is z mph. It's not like one time 3rd at 11k your bikes doing 90 and next time your run it up in 3rd it's a 140.

I agree with Rook. If you put a 55 on there it'll be right at what your speedo says.

I crunched the numbers and my ZX-14 speedo is reading ~20% too high at both 110 mph and 120mph so something is wrong. I've heard there is a lot of GPS lag so if you accelerate rapidly to high speed and then decelerate quickly it might not record the max speed. I have the iPhone switched on and set to record max speed and tucked in my jacket pocket and I'm just looking at the highest speed attained on a run and comparing it to the highest reading I saw on my bikes speedometer. ZX-10R and CBR1000RR were both dead nuts on doing it this way. Healtech says most factory speedos read 8% too high, that's not too bad but 20% is crazy. I find it hard to believe it's that far off. Stock gearing and 55 cross section tire, should be close.I think I'll mount the iPhone with Velcro on my instrument cluster so I can see it as I ride, then cruise at a constant speed on the freeway and check it for accuracy that way.

The speedoHealer online calculator says calibrate -20.8%. Your 20.8% fast on run #1. Run 2 is about 19.8% fast

http://www.healtech-electronics.com/ht_sh_online_calculator_en.html

faster you go, the more it is off.

First let me say Kruz I thought you had a Gen 2.

Are you running stock gearing? Are your tires worn? Both of these can affect your speedomter error. Gen 1s are particularly susceptible to lower final drive ratios since speedometer is read from transmission. Tire wear will increase speedometer error, as the tire starts off with around 6 mm of tread and over time gets down to 1mm or so. The tire's diameter is reduced thus it takes more revolutions (slightly) to cover the same distance. Similar to what Rook says about 55s, it's basically like going down a tooth on the rear.

20% sounds very high. I'd guess you're running a couple teeth larger rear sprocket or maybe 1 tooth smaller front, and/or your tires are not new, at that perhaps a smaller diameter /50 series compared to the stocker. This plus the factory 7% = 20%? Still seems very high. Something might be wrong with your ICP or associated wiring or sensors.

Gen 2s aren't affected by final drive ratio and speed because speed is read by wheel speed (ABS disk). But they would still be affected by wearing tire.

My muzzy Bonneville box and a gps helped me correct my speedo error on my 07, It also lets you run past the limiter by tricking the electronics into thinkin its in a different gear. I have had no problems with this setup and it works great and very easy to set up and doesn't affect your gear selection on the dash.

Rook, I can't open that link, just a blank screen.

First let me say Kruz I thought you had a Gen 2.

Negative Vic, I was one of the first guys to buy a ZX-14 and join the original forum back in June 2006, so an old timer. Me, Hub and 1Bad are about the only ones left from that era. I think I'm the only one left with an '06 14 from that original group, coming up on it's 10th birthday soon and still looks and runs like the day I bought it.

My gearing is stock, my tires are new and 55 cross section so that should help if anything, inflation is 38 psi F and R. Something is way off in my electronic speedo drive or I'm getting a GPS error.

* Last updated by: Kruz on 2/13/2016 @ 6:38 AM *

Rook, I got it to open but that is not a calibration chart, simply an online calculator for the mathematically challenged. You have to know the actual speed of your vehicle from another accurate source (GPS , Radar, etc.) to use it.

What I am looking for is an actual published speedometer error factor for the 2006 ZX-14. In other words someone has gone in and done the homework and determined these things are X% amount off as delivered from the factory with stock gearing, new tires and correct tire inflation pressure.

I don't believe I'm anywhere near 20% off, that doesn't pass the smell test. I know the freeway speed by my house is normally about 70 mph and I would have to be running 87.5 mph indicated on my ZX-14 to keep up with traffic with a 20% high reading error. I'm running more like 75 mph indicated on the 14 in traffic.

They say GPS doesn't lie though, so I have some analyzing to do to figure this one out.

My muzzy Bonneville box and a gps helped me correct my speedo error on my 07, It also lets you run past the limiter by tricking the electronics into thinkin its in a different gear. I have had no problems with this setup and it works great and very easy to set up and doesn't affect your gear selection on the dash

Rook, I can't open that link, just a blank screen.

You need to have Flash installed on your Mac or PC. It works with Android or iOS too but you would need to get the SH app. No biggy, it's just a calculator that you set your speedo reading and GPS reading in and it gives you the proper correction %. Nothing you can't do with your pocket calculator. 120mph x X% = 95mph X%= how much your speedo is off.

I was one of the first guys to buy a ZX-14 and join the original forum back in June 2006, so an old timer. Me, Hub and 1Bad are about the only ones left from that era.

don't forget Romans...and prolly Grn who was blue06 back then. Remember BadinBlack?? LOL that's who got me saying "prolly" (but I don't say it in real life). BadinBlack was knowledgeable on top speed limiter disablement and stock speedo error. He would know what is normal. This was a big topic back then. You will probably find old threads on this forum if you use SEARCH. I'm not so sure 20% is ridiculous for the Gen1. According to some old pics I have, looks like I set my SH to -08% with 45T sprocket and 190/55 tire. Could check my maintenance log to verify that if you want.

What I am looking for is an actual published speedometer error factor for the 2006 ZX-14. In other words someone has gone in and done the homework and determined these things are X% amount off as delivered from the factory with stock gearing, new tires and correct tire inflation pressure.

I'm sure plenty of people have compared their speedo to a dyno or GPS. I think you have everything you need to figure this out yourself. Get a SH on there and set it for -20% and see how you run against your GPS and another vehicle. That's as accurate as you can get. One of the problems with competitive LSR is determining exact speed. There are discrepancies even with radar, laser and GPS. LOL I guess you could get your hands on an aircraft speedo. That should be accurate as long as there is no headwind.

I don't believe I'm anywhere near 20% off, that doesn't pass the smell test. I know the freeway speed by my house is normally about 70 mph and I would have to be running 87.5 mph indicated on my ZX-14 to keep up with traffic with a 20% high reading error. I'm running more like 75 mph indicated on the 14 in traffic.

The error is not constant; it increases with speed. Where have you been mon frere? This is old news.

If you have a camera do some testing with highway markers. For comparison sakes, also include GPS results.

Record a few miles at x (constant) speed. I'm sure you've got a good, flat 3-5 mile stretch of interstate or marked highway. If you record 5 miles at 85 mph, and you end up taking the time for 77 mph then you have 8 mph or 10% speedometer error. Of all the errors I've seen about Gen 1, it should be 7% once at highway speeds or above. You're only limited by your bravery as far as how fast you want to measure. If you run test at lower speeds and their consistent it's probably worth running a mile or two at triple digit speeds and seeing what the results are. When I did my speedo error test I ran 70 and 85 for 3 miles.

Also, we can figure oot your actual speed too just using math. The circumference of your tire is known, and the rpms of your engine is know, and the final drive ratio is known for x gear. Granted, if you don't know your tack is accurate this can be an issue and you might be having problems with that too if you're having ICP issues.

Not sure if you want to measure accuracy during acceleration. That's a lot trickier and generally I can't see you looking at the speedometer anyway.

60 minutes / mph * seconds in a minute = seconds to cover 1 mile
60 / 85 * 60 = 42.35 @ 85 mph

OK tried somthing a little different. Mounted the GPS Iphone to the top of my gas tank with adhesive velcro strips on the ZX-6r and went for a run through the twisties.

Even the 600 acelerates so quickly compared to my truck that there was huge lag on the GPS, 20-30 mph under even light acceleration until you stabilized your speed. You have to cruise holding a very steady throttle to get an accurate reading but it came out right at 70 mph on the GPS for 75mph indicated on the speedometer which is about 7-8% over. About what I figured

Interestingly, I hit the first sharp bend at about 70 mph and the display flipped upside down. I hit the next turn at about 85 mph and the screen went completely blank like my iPhone died.

I rode home and hooked it to the charger and got the white apple sign and then it rebooted and came back to life.

Weird, I can't even explain why it did that, never seen anything like that before with an iPhone.

OK my theory on the ZX-14. I was nailing the throttle hard yesterday, accelerating to high speed and then getting out of it. That thing pulls so hard it probably had 40 mph turbo lag on the GPS reading and the GPS never caught up.

I'll try the 14 again, but this time steady cruise speed on the freeway with no turns, apparently tight turns confuse the GPS and cause the iPhone to shut down.

Kruz - I've never heard or experienced anything positive about the accuracy of smartphone GPS apps, when using cell towers.

Now ... there is a GPS app called OsmAnd that uses the satellites just like a stand alone GPS, and you can download map data from their site for it ... and it works whether you have a cell plan or not, cuz it doesn't need the cell towers, only satellites. I have it on an old Droid my buddy gave me and which has no cell plan. Can't make calls on it, but it works as a GPS It's also so old, he gave it to me free, so it doesn't even bother me when it gets wet ... and it has gotten wet, and it does still work

BTW, my buddy with a 2012 Concours said the same as Rook: That switching to a 55 series rear tire corrected his speedo.

OK, just did a GPS calibration run on the ZX-14, 15 miles of steady cruising on the highway with the iPhone velcroed to the top of the fuel tank just like I did on the ZX-6R. Way better results this time, I feel much better now!

The 14 has stock gearing and a 55 cross section rear tire which tends to correct any speedo error to a degree due to larger circumference.

30 MPH = 30 MPH GPS
40 MPH = 40 MPH GPS
50 MPH = 50 MPH GPS
60 MPH = 60 MPH GPS
70 MPH = 70 MPH GPS
80 MPH = 80 MPH GPS
90 MPH = 85 MPH GPS (Note: Tried this three times with same results each time.)

So at normal freeway speeds I appear to be dead nutz on and between 80 and 90 MPH there is some kind of divergence beginning. I did not try higher speeds due to traffic considerations and the presence of local law enforcement.

Strangely, although I don't recall going past 90 MPH the GPS max speed hold function recorded 102 MPH for this trip. Maybe I juiced it for a split second? These bikes accelerate so bloody quick....lol!

Anyway, I want to do this for all my bikes and find out which ones are off, by how much and at what speeds.

I also am now curious what the speedo deviation curve is on the 14 as speeds go higher, let's say 120 to 130 mph and above.

I need a really long straight stretch of road with no traffic and LEO to do this as you must hold absolutely steady speed to get the GPS to record accurately.

kruz - You may have missed my post, but my opinion is you're wasting your time trying to establish anything accurate with a smartphone GPS that gets its data from cell towers. Your device needs to get data from satellites.

Yep, get a real GPS receiver not a cell phone that acts like one

I got that, any ideas on where to pick up a reasonably priced GPS receiver? Price?

I would check Ebay for a used Garmin. People often just buy a new GPS when the road maps get out of date. Outdated maps still work pretty good for navigating new construction. my non-updated Garmin is about 20 years old and will still get me on the right path eventually even after highways are rerouted. All you need is the GPS guided mph function and that works everywhere regardless of the maps. Even works in an airplane. LOL the top speed on my Garmin is 545 mph!

* Last updated by: Rook on 2/14/2016 @ 8:32 PM *

Check to be sure the Garmin will stay charged long enough without a power outlet.

Just tested mine against Garmin GPS. With 200/55 tire that has slight center wear, 45 T sprocket and Speedohealer v4 set to -11%, the stock speedo is dead on at 55, 70, 80 and 90 mph. The SH setting was acquired by referring to SH estimated tables for a 190 tire and 17/45 gearing. a 190/55 is probably about the same diameter as the tire I now have on the bike. I didn't want to try it over 90 because you do need to keep the speedo steady for about 1.5~2 seconds and also be looking down at the Garmin in your hand.

Garmin stayed charged for over 30 minutes and then low battery message appeared.

* Last updated by: Rook on 7/12/2016 @ 1:03 PM *