 Speedometer Inaccurate
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Joined: Jul 2009
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I don't see any previous posts, but I suspect others have discovered that their speedos aren't calibrated accurately - mine reads about 7 mph too fast, which also probably gives me false mpg and trip meter readings! Is there any way to adjust the speedo to make it closer to real speed? 
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Re: Speedometer Inaccurate
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Joined: Jan 2005
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Loquacious
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Loquacious
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Yep.. they are a bit off. I just basically try to forget about it, it helps keep me out of trouble...  I suppose a larger circumference front tire would do it.. dunno about the math though. It seems like there was some discussion about it some time back.. might do a search and come up with something.
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Re: Speedometer Inaccurate
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Joined: Jan 2005
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Bar Shake
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Bar Shake
Joined: Jan 2005
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If you didn't see any previous posts, you didn't search very well.
Was a major topic of discussion for some time. Usually about 10% optimistic.
Contra todo mal, mezcal; contra todo bien, también
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Re: Speedometer Inaccurate
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Joined: Jan 2005
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Should be Riding
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Should be Riding
Joined: Jan 2005
Posts: 12,164 Likes: 1 |
Quote:
Usually about 10% optimistic.
Mine too.
Actually, its been a while since this has been brought up.
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Re: Speedometer Inaccurate
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Joined: Jan 2008
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Didn't someone say the odometer was accurate even though the speedo is off?
Its more fun to be ridin'! I'm still ridin 
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Re: Speedometer Inaccurate
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Joined: Jan 2005
Posts: 12,164 Likes: 1
Should be Riding
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Should be Riding
Joined: Jan 2005
Posts: 12,164 Likes: 1 |
Yes, which, to me, doesnt make much sense.
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Re: Speedometer Inaccurate
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Joined: Feb 2010
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some cars are also a bit optomistic in their speed, but the milage is right. My little Kia is usually thinking it is going 4-6 miles faster than it truely is. I don't think it is a big problem.
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 Re: Speedometer Inaccurate
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Joined: Jun 2006
Posts: 2,626
Loquacious
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Loquacious
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Quote:
I don't see any previous posts, but I suspect others have discovered that their speedos aren't calibrated accurately - mine reads about 7 mph too fast, which also probably gives me false mpg and trip meter readings! Is there any way to adjust the speedo to make it closer to real speed?
What size front tire do you have?
If you change to a slightly taller one, it will slow the speedo down.
A 110/80 has an 88mm sidewall.
A 100/90 is 90mm.
A 130/70 is 91mm.
But the big change is a 120/90- 108mm, it should slow
your speedo down by 22%.
Steelheart- '03 Speedmaster Black/Yellow
The Hayabusa Killa
16" Shorties/140 mains/Airbox drilled
Procom CDI
"There is no cure for Celibacy. But we can treat the symptoms."
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Re: Speedometer Inaccurate
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Joined: Jan 2007
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Quote:
Didn't someone say the odometer was accurate even though the speedo is off?
with mine i can go thru the local speed trap which is in a 100k zone with the needle sitting on 120kph at just under 4000rpm,s
according the the Gearing Comander chart the rpm is 100kpm for the gearing on these bike's
the odometer tho i check when i see a sign post ie: Esk 50k take note of the reading recheck when i get to Esk,the reading is all most spot on at 50k
2 things i think you'll find with the speedo
1- the needle is spring driven hench the difference in reading's from bike to bike
2- the odometer is gear driven
Benny
04 yellow&black Speedmaster+the Money Pit{xj jeep}
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Re: Speedometer Inaccurate
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Joined: Mar 2005
Posts: 2,419
Oil Expert
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Oil Expert
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Quote:
What size front tire do you have?
If you change to a slightly taller one, it will slow the speedo down.
A 110/80 has an 88mm sidewall.
A 100/90 is 90mm.
A 130/70 is 91mm.
But the big change is a 120/90- 108mm, it should slow
your speedo down by 22%.
I think changing from stock to a 120/90 only slows your speedo down about 6% - but hey I've been wrong before
Cheers, Richard
~~~~~~~~~~~~
09 America, Staintune Pipes, K&N, Breathe, Hagon Nitros, AI & O2 removed, tune 20184 (modified), MTX-L a/f gauge
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Re: Speedometer Inaccurate
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Joined: Jan 2007
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Adjunct
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Quote:
Quote:
What size front tire do you have?
If you change to a slightly taller one, it will slow the speedo down.
A 110/80 has an 88mm sidewall.
A 100/90 is 90mm.
A 130/70 is 91mm.
But the big change is a 120/90- 108mm, it should slow
your speedo down by 22%.
I think changing from stock to a 120/90 only slows your speedo down about 6% - but hey I've been wrong before
I'll agree with you on this 1 Richard
the difference in radius between the size's at most is only 20mmish so by the time 1 is to do the pye r squared thingy its only about a extra 120mm in circumference i'll do a roll out with mine with the 12/90 tomorrow and just see what it is
am thinking the roll out will be say 2.1 to 2.4 meteres so yeah something along the lines of 4-6%
Benny
04 yellow&black Speedmaster+the Money Pit{xj jeep}
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Re: Speedometer Inaccurate
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Joined: Jun 2006
Posts: 2,626
Loquacious
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Loquacious
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Hey, it was late, I just did the simple math.
You're right, it won't slow it down as much as I thought.
But a 120/90 or even a 130/90 is still the best bet to fix the speedo.
Steelheart- '03 Speedmaster Black/Yellow
The Hayabusa Killa
16" Shorties/140 mains/Airbox drilled
Procom CDI
"There is no cure for Celibacy. But we can treat the symptoms."
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Re: Speedometer Inaccurate
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Joined: Jan 2007
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Quote:
Hey, it was late, I just did the simple math.
You're right, it won't slow it down as much as I thought.
But a 120/90 or even a 130/90 is still the best bet to fix the speedo.
its all good Buddy were not here to take the ****** outta people to often
come to think of it ,its happened to me a few times at that 
04 yellow&black Speedmaster+the Money Pit{xj jeep}
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Re: Speedometer Inaccurate
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Joined: Aug 2005
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Loquacious
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Loquacious
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My speedo at a steady 78 mph is actually 73 according to the GPS. Strangely enough, my odometer reads a little less miles than traveled.
Bob
2005 America, 904cc - sold. 2014 Trophy SE.
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Re: Speedometer Inaccurate
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Joined: Jul 2009
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Thanks for all the input. If anyone knows where to find the previous discussion please let me know. My concern is that I have a BMW, Honda and SM all w varying accuracy, the SM being the least accurate - about 7-8 mph too fast according to GPS. Up to 5 is easy to live with, but this is about 15% off reality. Of course the BMW is spot on, just to cause trouble! Also what Benny said about the speedo vs. the odometer makes sense. Thanks for the explanation. 
Last edited by jim5968; 03/08/2010 6:15 PM.
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Re: Speedometer Inaccurate
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Joined: Jan 2005
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Bar Shake
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Bar Shake
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Here's one. Search the miscellaneous forum for more. linkYou might search for top speeds or similar too. Some people actually think these bikes will do 120mph
Last edited by bigbill; 03/08/2010 7:27 PM.
Contra todo mal, mezcal; contra todo bien, también
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Re: Speedometer Inaccurate
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Joined: Mar 2009
Posts: 12,964
Stickman Yogi
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Stickman Yogi
Joined: Mar 2009
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Yup, the 120/90 front tire pretty much sorted out the speedo inaccuracy (when it worked) for me. I don't know... maybe it's a good thing to think we're going faster than we are.
Live to love, love to live.
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Re: Speedometer Inaccurate
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Joined: Jan 2005
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Check Pants
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Check Pants
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Quote:
I don't know... maybe it's a good thing to think we're going faster than we are.
That may be true, but it doesn't explain the kindly Royal Canadian Mounted (in a sedan) Police officer handing out tickets last summer. Had we still been in Montana, we would have received tickets for impeeding, not speeding 
jh
"It's not what I say that's important, it's what you hear" Red Auerbach
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