Speedometer/odometer error

First of all

Hello all!

I'm new to the forums and new to the bike. Bought a 2002 VFR on Saturday and I'm loving it. During the course of shopping for the bike, i test rode a few and noticed the speedometer on the 6th gen bikes is a little optimistic(10% or so). The bike i finally settled on has a -1 tooth front sprocket so its speedometer is even more optimistic. What I'm wondering is if I can expect the reduced gearing to effect a corresponding change in the rate i add miles to the odometer, thus deluding me into thinking I am going farther and getting better gas mileage than I really am? It seems it should (assuming the speedo/odo sensor is on the transmission output shaft (is it?)), however on my commute to work this morning was nearly identical to the distance reported by my Kawisaki Z-750s and both bikes are within a mile of the distance as measured using google maps. Has anyone else had any experience with gear ratio changes and odometer accuracy? Also are there any quick fixes/products for adjusting the speedometer to be more realistic?

Thanks a lot, I'll be seeing you all around.

 

Speedometer error

That is a good question about the speedometer and odometer. Your situation is a little different with non-stock front sprocket. How did you guess the 6th gen you rode was off on speedometer? I've been having that exact problem with my 6-month old 2007, completely stock. Speedometer seems about 10% fast. Tested against my bros car on highway, he was at 80 and my VFR was reading 90mph. My odometer seems correct based on highway distance test but my gas mileage (avg 36 mpg) for new 6th gen has been kinda low compared to what others have reported. Maybe I need GPS to get exact distance/speed? Problem common to all 6th gens?

 

Problem common to all motorcycles...

If I am not mistaken, speedometers have to be by law...Up to 10% over actual speed, but cannot indicate under actual speed. So to keep it for indicating faster than actual speed when leaning through a corner on the edge of the tire, and therefore reduced circumference of the the wheels, the speedometer would have to be optimistic in a straight line, while running on the largest circumference of the tire.

Also, the Odometer is accurate for straight line travel, not the reduced circumference while leaning through a corner. So, that means if using a GPS, the speed will be indicated as up to 10% higher than actual, but your total distance traveled should be accurate.

Hope that's not too convoluted to understand. There are much more knowledgeable members on this forum, so hopefully some of them will weigh in on this.

 

Speedo Healer?

HealTech Electronics Ltd. - Makers of the SpeedoHealer, GIpro and X-TRE -

 

Mine had 20% error after -1/+1 sprockets. I used Speedo Tuner and a dyno to calibrate mine, works great.

 

I did some checking around, and found that the dealers all say that all manufacturers for motorcycles have the same inherent 10% deviation. I checked some more and found out why. Honda, and other electronic-system motorcycle manufacturers build ECM's in batches. They start with the prototype bike and tweak all the settings until the average numbers are in a safe zone.

There are a lot of variations in a bike that can change individual speeds, and they're not going to tweak each bike before it goes out the door. Too expensive. Tire pressure, tire size, tire brand, variations in tire curve, sprocket tooth sizes, chain length, weight on the bike, tire density, air temperature, etc., etc., etc. These all play a factor in the accuracy of the motorcycle's speedometer. I'm sure there are many more things that factor in.

But it's illegal for a manufacturer to sell a bike that reports going slower than it is. That would cause the rider to unknowingly break the law, and potentially endanger him if the speed is beyond momentary control. So while the average bike is around 10% deviation above normal, it's really a law of averages that the manufacturer uses to ensure that no bike ships with a speedometer breaking the law. But they cannot exceed 10% by law either.

I called the local shops that have dynos and they said that their dynos have between 5-10% speed deviation, so you're not going to get a whole lot better results if you're reprogramming on one of those. Your best chance for a dead-on speed setting is to use a laser...and that can get a little complicated (and weird). Plus, you still end up with tiny variations such as rider weight, temperature fluctuations, tire pressure, etc. You can get more accurate, but going for "on the nose" speed is probably going to have inherent problems of its own.

Cars are also inaccurate for the same reason, but to a much smaller degree.

I agree that 10% is pretty high. I'd shoot for 2%, but 5% would still be fine for me.

This also makes me wonder if this is why when a cop gets you for speeding, have you noticed that they usually take 5 miles off the speeding charge? Wonder if that's why...

 

The easiest and cheapest way to get around the problem is to use a bicycle computer that runs off the front wheel. That's what I've used since I got my 5th gen 9 years ago. Doesn't matter what the sprockets are, just recalibrate when putting on a new front tire if necessary. The only downside is no lighting for after dark riding.

 

They must be using some shitty dynos. Mine reads to .01 MPH and has accuracy of +/-1% according to the manufacturer.

 

The dynos of the places I checked have the DynoJet 200 series. There's a Harley Davidson shop here with the latest top-of-the-line DynoJet model. I'll give 'em a call and see if theirs is better. What brand dyno did you use for such tight correction?

 

Mine is a Mustang RG-3000. It's an automotive dyno, you won't find one in a bike shop. I cannot believe a Dynojet or any other commercial dyno can be that far off. On those cheaper Dynojet inertia dynos they use speed vs time to calculate hp, so speed needs to be very accurate.

 

Search for speedohealer and also sprocket. I pasted a couple of links below.
I don't have personal experience using one, but after digging through forums I found that it can address the speedo/odometer error. I ordered one (healtech brand for a 2000 vfr) because I'm going down a tooth in the front when I change my chain and sprockets. I might be able to get away with setting it for a 6% change and it should behave like stock, but not correct the original error. To remove the inaccuracy you need to characterize the error using an independent device, such as a gps or other speed device. Basically you have to tell the device how wrong the original signal is, and it adjusts the signal going to your speedometer and odometer.


http://vfrworld.com/forums/sixth-ge...-change-speedometer-correction-questions.html
http://vfrworld.com/forums/sixth-generation-2002-2009/25113-chain-sprocket-time.html

 

I've got a Speedohealer on my Gix750 to correct an 8.5% error. Totally easy to program and possible to have two separate settings in case you change wheel/tire sizes. Got tired of doing math while riding and wanted to keep the add'l miles off of my odometer. Interestingly, my Buell XB speedo is EXACTLY correct.