MPH are off!

[Kruse08]

Was wondering if anyone has had the same issue and if there is a fix. The 99 250 I have is around 5-10mph off compared to other bikes. While I am doing 70mph my speedometer reads 80mph. I tested this while riding behind my friends bike. I also have been informed by two other ninja 250 riders that this is a common issue. I wanted to know if there is a fix for this. Could it be the speedometer cable? Clutch cable to tight or something a long those lines. Just wanting to know. I did research before posting this but did not find anything particularly the same. Thanks for any info.

[DaBlue1]

Tire diameter can affect speedo readings to a small degree. What is the actual diameter of yours? (not sidewall numbers)

The speedo on the bike is an eddy current speedo. Lots of room for error in this type of mechanism.

[choneofakind]

Very common. Easiest fix is to run a 100/90-16 front tire. That will get the speedo reading closer to correct.

[Kruse08]

Thanks, I will check my tire sizes when I get back into town. I will let you know what the tire sizes are because they are newer tires which were put on by the previous owner.

[cbinker]

use a GPS.

[cadd]

Originally Posted by DaBlue1

Tire diameter can affect speedo readings to a small degree. What is the actual diameter of yours? (not sidewall numbers)

This is true. Different tire manufacturers may show the same tire size on the sidewall but the actual size may differ slightly.

In bicycling, to get the most accurate speed reading, we have to measure the circumstances of the tire. To do so, you mount the bike and place the stem of the front wheel at the 6 o'clock position. Roll forward one revolution until the stem is at the 6 o'clock position again. Use a tape measure to measure the distance traveled. Input that into the settings menu of little speedometer to get the most accurate reading.

If I remember correctly, Michelin and Continental had a pretty large difference in circumference reading of the same size tire (700x23 in my case) which would lead to a 1-2mph difference at 20mph.

If you do the circumference reading on your tires, I'll help you out be doing one on my stock IRC tires to see if there's a significant difference.

Also, have you checked your tire pressure? Are you a big guy? This may attribute to the difference as well.

[Kruse08]

I have not checked my tire pressure in a while but need to do so and no I only weigh 140lbs. Owning a bike is new to me even though it is like a car with maintenance. I just have not gotten around to doing any maintenance or anything yet as I am short on cash. Doing a lot of research and reading on what to do and how to do it. I have noticed a few things so I thought I would ask so I could get a little direction as for what to look for.

[InvisiBill]

In my experience, all bike speedos are optimistic. I've heard that it's set high enough that any tire you could fit on the bike would not cause it to exceed the indicated speed. No idea how true that actually is though.

The VN700's spec sheet even lists the amount of speedo error. http://www.invisibill.net/vulcan/VN700spec.jpg

SPEEDOMETER ERROR
30 mph indicated	29 mph
60 mph indicated	55 mph

The EX500 is similar, with 65mph on the speedo matching up to ~60mph on my GPS.

[capt_bugaloo]

Or just subtract the 5%-10% in your head.
If the odometer says 65 mph, just knock it down to 60mph as your actual speed.
Not that hard to do...

[Kruse08]

I have already calculated the difference with what my speed is and the actual speed is. Just wanting to know if there is a fix for it so when i ride on the highway my rpms arent at 10k while doing 80mph which is really 70mph.

[alex.s]

Originally Posted by Kruse08

Just wanting to know if there is a fix for it so when i ride on the highway my rpms arent at 10k while doing 80mph which is really 70mph.

buy a gsxr1000

[Kruse08]

Nah, not anytime soon. Sounds all great and dandy until my insurance payments.

[NevadaWolf]

I know this is for the pregen, and I have a newgen, but it might help.

I got an electric gauge that allowed me to program in the circumference of my front tire. Doing that and adjusting it up and down as I rode back and forth on a short empty road allowed me to get my speedometer to within 0.3 MPH of what the GPS was reading.

Might help if there is a pregen gauge available. I got mine from Koso.

[Kruse08]

Front tire is 100/80/16 and rear is 130/80/16

[Ninjinsky]

Tyre profile or even wear. On my car I notice as the tires wear down at 60 it adds about 3mph relative to the sat nav as the tires get low.

[choneofakind]

You can see the effect of different tires on the speedometer readout here:
http://faq.ninja250.org/speed/#noredir

You can also play with different gearing to see how it affects engine RPM at various speeds.

[agentbad]

I actually tested mine using a simple GPS app on my phone called GpsTTS. It was originally made for skiing/snowboarding but works for pretty much anything. I set the app to only trigger over 55mph then give my 20 second voice updates so I could match it to my speedo. After switching over to new Kenda tires my speedo is actually pretty close to accurate now. It's actually pretty sweet because it will warn you if you're getting to crazy with the throttle and even turn you music down to give the speed.