Speedometer not acurate

[PaleHorse]

As I dig deeper into my GSXR, I keep finding more issues. (I picked this bike up a few months back) The speedometer is roughly 20% off. On the freeway, it will show 100 MPH and my GPS says 80. This is pretty accurate from 0-100.

My first inclination was that the sprockets had been changed from factory but that is not the case. With the rebuild of the cooling system. I pulled the front sprocket cover off last night to get to one of the radiator hose clamps. The front sprocket is 17 teeth and the rear 43. This is factory.

There is a power commander in the tail so I thought that there might be a speedo healer wired in. I'm 100% certain this bike was a track bike in its past and one of the prior owners may have ran different sprockets. Everything on the bike is wire tied for the track. There is not a speedo healer.

What would make the speedometer read 20% off with everything set at factory specs?

 

[dravnx]

Many, many speedos are not accurate. It's has to do with the laws in Europe. Speedo accuracy has a tolerance for reading high but the tolerance for reading low is +- 0 so they are designed to not exceed that tolerance.

 

[cal scott]

Many, many speedos are not accurate. It's has to do with the laws in Europe. Speedo accuracy has a tolerance for reading high but the tolerance for reading low is +- 0 so they are designed to not exceed that tolerance.

Thanks for that explanation :thumbup. Always wondered why almost all speedos read high. My V-Strom is around 10% on the high side :x.

 

[295566]

Cheapest, easiest, and smallest installation.

 

[dravnx]

Yep, my Vstrom is 8%. I have a GPS permanently mounted with speed displayed so I've gotten used to using that.

 

[PaleHorse]

Thanks for that explanation :thumbup. Always wondered why almost all speedos read high. My V-Strom is around 10% on the high side :x.

20% seems excessive.

Looks like the only way to correct it or at least get it more accurate would be installing a speedo healer or calibrator like the one linked above.

 

[stangmx13]

smaller rear tire? actual tire circumferences are all over the place, even btw tires of the same "tire size". itd be difficult to compare to whatever came stock on an older bike.

 

[ichabodnt650]

Is the odometer also off by +20% ?

 

[CDONA]

My hyper owners manual sez, 8% high. I think this is done on purpose by congress, along with all the rest of moto safety regulations to save us from ourselves.
My Freightliner was spot on using those radar speed warning signs.
I know my triumph reads faster than I'm going by 5 mph @ > 40 .

 

[PaleHorse]

Is the odometer also off by +20% ?

There is only an electrical connector running to it so it's 100% digital.

20% more miles than the bike actually has on it kinda blows.

I just replaced the tires it had a 180/50/17 and replaced with the same. That's the stock size.

 

[295566]

There is only an electrical connector running to it so it's 100% digital.

20% more miles than the bike actually has on it kinda blows.

I just replaced the tires it had a 180/50/17 and replaced with the same. That's the stock size.

Crown size can vary between manufacturers or even models, which will alter the circumference of the wheel. Larger circumference = faster, smaller = slower. This can make your speedo off even more.

Regardless, almost all modern bikes are off from the factory. Not sure why this is. Purchase the SpeedoDRD I linked above and never worry about it again! :thumbup

 

[stangmx13]

There is only an electrical connector running to it so it's 100% digital.

20% more miles than the bike actually has on it kinda blows.

I just replaced the tires it had a 180/50/17 and replaced with the same. That's the stock size.

Surely you mean 180/55 :wtf

 

[mototireguy]

Moto speedos have always been mildly inaccurate. But 20% is more inaccurate than average.

+1 non-stock tire size can have an effect.

+1 non-stock front/rear sprocket tooth count.

 

[PaleHorse]

Surely you mean 180/55 :wtf

You are correct Sir.