speedometer vs gps

So I put the gps on my bike today for the first time. My bike has the110/90 on the front so I thought it was accurate. Put the GPS on it cause I wanted to get some times for 0-60 and Qtr mi times. At speedo showing120 GPS was saying111mph. How can I get speedo closer to being accurate? My Vulcan is the same way but it still has the stock100/90 tire on it so I expected it to be off

Funny I should read this as I did same thing a couple weeks ago. used GPS feature on my phone on a ride and placed it on top of my tankbag to see how accurate my speedo was since I read somewhere the old KZ were notorious for showing higher speeds than real. Sure enough at 100kmh (sorry for metric numbers)my GPS said i was only doing 83kmh. at 120 on speedo GPS said i was 105. a 15kmh error!!! that is huge. my tires are stock size and I have kept bike pure stock otherwise too. Can't think of anyway it could be recalibrated either since speedo is sealed. Bike is a 79' KZ1000st shaftie.

mine might land me in jail.... among other offenses that woulda went un noticed. mine is not only off but hangs up and down. so if im doin eighty i gotta pay attention cause if traffic is passing me its more like its hung up at eighty and im not doing the 70 i thought i was.

:laugh: all Kawis are this way straight from momma Kaw. Right at 10% off. That's why I put the GPS on each one to figure out how to ride it in traffic. I try to run 60-65 in a 55 zone. Run 72-80 in a 65. 77-85 in 70mph zone...etc. So at a buck fitty indicated, yup, 135 actual.

I dont get this? It's my understanding that transportation dept has a law that requires speedometers to be accurate. does that only apply to cars?
And yes I agree, they all are, my 06 Vulcan is 10% over on the money.
I think the only way they are accurate is if they are BROKE! :laugh: :laugh:

kzcurt wrote: I dont get this? It's my understanding that transportation dept has a law that requires speedometers to be accurate. does that only apply to cars?
And yes I agree, they all are, my 06 Vulcan is 10% over on the money.
I think the only way they are accurate is if they are BROKE! :laugh: :laugh:

when the bike is parked.

Send your gauges to Z-Resto to be rebuilt, they are supposed to at least go back to original spec after rebuilding but as stated above, they will likely always be inaccurate to some extent. GPSs are not 100% accurate either, nor are car speedos whatever regulations may exist. 90% of vehicle speedos will read high.

D.O.T. does require all vehicles speedometers to be within............are you ready..........
5 mph at 50 lol!!! thats within 10% or about what all kaw's are off!
www.fmcsa.dot.gov/rules-regulations/admi...text.aspx?reg=393.82

There is a cure.

I took the cover off removed the needle and relocated the needle to the correct position and presto. 1 accurate speedo.
I used my gps and did a couple of calibration runs until I got it exact.

Very simple realy.

I use an autometer electric speedo driven by a gps sending unit. I trust it for the most part but it will vary up and down going thru hilly areas and sometimes wooded areas. Local officer tried to tell me to take it and get it calibrated, yeah, right! On a machine that doesn't move with a speedometer that is driven of of bikes location. He didn't get it. :laugh:

Les Holt

les holt wrote: I use an autometer electric speedo driven by a gps sending unit. I trust it for the most part but it will vary up and down going thru hilly areas and sometimes wooded areas. Local officer tried to tell me to take it and get it calibrated, yeah, right! On a machine that doesn't move with a speedometer that is driven of of bikes location. He didn't get it. :laugh:

Les Holt

"He didn't get it." Some do and some don't. I like the ones that do get it a lot better :laugh:

That's why I check mine with GPS, so I'll know more accurately what speed I "think" I'm going :silly:
and what speed Johnny law should see on his radar.. about 10% less than what my Kawi speedo indicates

On a different note. There are some guys that swear by the bicycle speedos, like the ones at Wally Whirld. I bought a Schwinn speedo for my mountain bike.

www.target.com/p/schwinn-12-function-bic...76&ci_gpa=pla&ci_kw=

BlackZ1R wrote:
On a different note. There are some guys that swear by the bicycle speedos, like the ones at Wally Whirld. I bought a Schwinn speedo for my mountain bike.

www.target.com/p/schwinn-12-function-bic...76&ci_gpa=pla&ci_kw=

I put a cateye bicycle speedo on one of my Z1s. It worked okay but topped out at 123km/h and then just read gibberish