Speedometer error?

[z10]

I went out for a ride this afternoon and for the first time took along a GPS to check my speedometer.

At an indicated 85mph I'm doing about 76, so the speedometer is reading almost 10mph faster than actual.  How to I correct this?

Thanks in advance.

[BuzzKill]

I could be talking out of my butt, but I think alot would have to do with tire size.  What are you running on the front?  Also I don't think there is an adjustment, but again I could be wrong.  My wifes bike has OEM tires I think, and hers indicates faster as well.

[Jess from VA]

All Japanese bikes are off 5% in the speedo (but not odometer), to avoid any draconian penalties by the US should there be any error the other way.

There are electronic fixes, including a GPS instead of the speedo.

http://www.amazon.com/s/?ie=UTF8&keywords=speedohealer&tag=googhydr-20&index=aps&hvadid=9257532939&hvpos=1o1&hvexid=&hvnetw=g&hvrand=120723603229331885&hvpone=&hvptwo=&hvqmt=b&hvdev=c&ref=pd_sl_6cloaxj088_b

http://www.yellr.com/yb_home.htm

[wizard -vrccds#125]

Thy are all that way. The only way to correct it would be a drive gear change and none are made. You can just go by your GPS as I do on both of mine. 

[R J]

I go by the GPS in all my vehicles.

The Dodge pickie up is the closest to the GPS.

There is only 2 mph difference in them.

The Toyota Highlander is about 8 mph fast.

[hueco]

My best friend is off by 5 mph. GPS reads 70 mph. Fat Girl's speedometer reads 75 mph. So on and so forth. NOW. I Know why I never got a speeding ticket.

[5_19]

Thy are all that way. The only way to correct it would be a drive gear change and none are made. You can just go by your GPS as I do on both of mine. 

My experience also. I also use a GPS to verify actual speed for different vehicles, and it varies a lot.

[Joevalk]

I fixed mine. 21" wheel. The speedo is rite on the money with a GPS

[z10]

Well, then GPS it is.  Really cuts down on my top end bragging though. 

[5_19]

Well, then GPS it is.  Really cuts down on my top end bragging though. 

In Texas it ain't bragging if it is so!
" I topped out at 130 mph according to my speedometer".

[Red Diamond]

No adjustment necessary for me, when I see 75, I slow down to 70. Guess that's why it takes me so long to get anywhere.

[z10]

Well, then GPS it is.  Really cuts down on my top end bragging though.  

In Texas it ain't bragging if it is so!
" I topped out at 130 mph according to my speedometer".

You know you are correct!  I think my valk has the potential to go ballistic.  Because after all....it's a Texas Valk!