TTS MasterTune speedometer adjustment
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Club Member
Joined: Aug 2008
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From: Yakima, WA
TTS MasterTune speedometer adjustment
According to my GPS, my speedometer shows that I am going 2-3 mph faster than what I am actually going. I'm sure that's OK, but I'm **** about accuracy, and I (apparently) can change it so I want to.
I don't need all the complexity of the VSS calculator with a 'tire rollout estimator' and all, I just want to know how much, and in which direction, to change the number in that pop-up window.
Can someone tell me?
Steve
I don't need all the complexity of the VSS calculator with a 'tire rollout estimator' and all, I just want to know how much, and in which direction, to change the number in that pop-up window.
Can someone tell me?
Steve
HD EFI Guru
Joined: Jan 2008
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I do not know the answer for you but getting the tire roll out is plenty simple to do. Place a mark on the tire where it meets the ground and mark the ground as well. Now sit on the bike and roll it straight forward until the mark on the tire meets the ground again. Transfer the mark onto the ground then measure between your two marks with a tape measure.
Outstanding HDF Member
Joined: Jul 2007
Posts: 2,609
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From: Indy area
Yeah, that's what I do. But I also go several revolutions and divide the resultant length by that number. Where the mark is closest to being at the ground is somewhat discretionary. By adding some revolutions you can minimize the "discretionary" effect for a truer reading.
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Joined: Oct 2007
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From: New England
I too used my GPS and found the HD speedometer overstated by about 4%.
So, I changed the TTS value for my bike by 4%.
Per the MasterTune help file:
a larger value will decrease the speedometer reading
a smaller value will increase the speedometer reading
Now my speedometer is right on.
Hope that helps!
So, I changed the TTS value for my bike by 4%.
Per the MasterTune help file:
a larger value will decrease the speedometer reading
a smaller value will increase the speedometer reading
Now my speedometer is right on.
Hope that helps!
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Joined: Jul 2008
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From: West OKC, OK.
Just my opinion, but I wouldn't use a GPS to gauge the accuracy of your speedo. Most non-military GPS units are only accurate to between 9 and 30 feet. Not close enough to determine if speedo is off 3-4 mph.
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Joined: Aug 2008
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From: Yakima, WA
I add this final post in case someone searches for this topic sometime. The magic number for me turned out to be 2130. Actually I started by adding 50 (as Old Fart suggested) to the original 2078, which resulted in 2128. It turned out to be less than 1/2 mph off in the original direction so rounding it up to 2130 seemed like the right thing to do.
Thanks! Steve
Thanks! Steve
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Joined: Oct 2007
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From: New England
Actually, the algorithm used to calculate speed is a bit different then the one used for location. Speed is really close (assuming good satellite reception).
But you are correct, location accuracy is skewed intentionally.
But you are correct, location accuracy is skewed intentionally.