Speedometer way off now

[bode61]

My speedometer was within 1 mph compared to my GPS for the first 11k. I replaced the tires (Metzlers) with Pilot Road 4's. I didn't notice at first on whether this was when my speedo started giving new numbers but now it is off by 8 to 9 mph. Bike says I am going 59 mph and GPS says 51. Bike says I am going 45 and GPS says 37.

Any ideas on what could have happened?

 

[BerndM]

Unless something happened in the firmware for your speedo, the only other option is that your new tires are a smaller diameter than your old tires.
This would most certainly account for a higher than actual speedo reading.
More revolutions needed for the same distance traveled.

 

[SergeantChuck]

I will double check mine but when I first switched to the PR4's my speedomter was still only 1MPH off. You have me curious so I will check on the way home and update my comment.

So if your driving down the road at what you bike says is the posted limit is everyone flying by you? Are you using the same GPS that you took the reading with when you had the Metzlers mounted? I used an app on my phone call Speed Tracker. Give something like that a shot and see if it gives you the same reading as your GPS.

 

[StratTuner]

The continental motion tires are also off by about 1 mile per hour. It's been that way above 45 miles per hour ever since I owned the bike

 

[ziggie]

Haven't had this problem with my pr4s,maybe your GPS is off.try it in your car and see if it is off.

 

[turbodieseli4i6]

My PR4's read the same as the PR3's and OEM 023's. Less than one mph off.

 

[Ruggybuggy]

The continental motion tires are also off by about 1 mile per hour. It's been that way above 45 miles per hour ever since I owned the bike

It funny you say that because my Conies resulted in exactly 5mph off. Bike's a 2014 750.

 

[showkey]

Avon Distanzia make the speedo off by about 2.5 mph @ 60 mph.

 

[bode61]

I double checked my GPS and it is right on the money with my Aprilia and my car.

 

[Russell733]

I have PR4s and never off more then 1-2 MPH from my GPS. I was actually surprised when I got the GPS how accurate the speedo reading was.

 

[showkey]

I double checked my GPS and it is right on the money with my Aprilia and my car.

What is the size of the new tires ?

 

[SergeantChuck]

I double checked my GPS and it is right on the money with my Aprilia and my car.

This may be a dumb question but I'll ask anyway. I have no idea how long you've had you bike or how many miles you have on it. I see you joined the forum back in Nov 2012. We know you have changed your tires but have you changed your sprockets? There have been several discussion over time about replacing the front sprocket with 1 tooth more and the rear with 2-3 less. Any chance you've done something like that? Just asking. Never hurts.

 

[bode61]

sergeantchuck. that might be it. i had a new chain and sprockets replaced. i was out of town so i had buddy drop bike off and the shop might have ordered true sprocket for the manual one not the dot which mine is. aren't the sprockets different for them?

 

[SergeantChuck]

I tried to find the thread that talked about this but could not. If I remember right it was 16 tooth front (both models), 39 tooth rear for DCT, and 43 tooth rear for the Manual. Someone that is positive please speak up. I'm going to do some more looking.

Edit: Found it. http://nc700-forum.com/forum/nc700-technical/4260-recommended-chain-sprocket-costs-2.html

 

[bamamate]

Yes sprockets and chain length are different on the DCT and manual.

 

[showkey]

39 to 43 is about a 10% change................sound about the right amount to account for the sudden change.

 

[bode61]

Just confirmed that shop installed a 43 tooth instead of the 39 tooth. They will replace it at their cost.

 

[SergeantChuck]

Just confirmed that shop installed a 43 tooth instead of the 39 tooth. They will replace it at their cost.

Awesome. You got it figured out. That's all that matters. I imagine you were a little worried at first.