Hi,
I've had the koso CRB Multifunction Gauge fitted on my firestorm, installed 6 magnets and set up the speedo as suggested in the manual.
It says roll the wheel to get the correct wheel circumference ( I'm getting 1850mm ) I've also tried setting it up to 1700mm the actual wheel size.
My readings are atleast 5% to 10% to low.
Has anyone installed one of these? Or got any pointers?
Koso aftermarket speedo calibration problems?
Re: Koso aftermarket speedo calibration problems?
What's the problem?
Use a GPS device or a smartphone app to validate GPS speed.
Compare with speedo reading and calculate the coefficient GPS divided by speedo reading.
Example : GPS 75 mph, speedo 70 mph, factor = 70/75 = 0.933
Then go to the speedo menu to show the actual wheel circumference value
Multiply this with the correction factor, enter and save the new value.
If the required value is smaller or bigger than the possible range for the radius, you need to play with the number of signals (i.e. program a higher or lower number than you actually have). In this case the entered "circumference" value has no physical relation to the real tire circumference.
Repeat GPS comparison to confirm everything is closer to where it should be.
Note that tire radius is a dependent variable. It changes under tire type/size, pressure and vehicle speed. So there is no such thing as "the radius" that you enter once and that is valid once and for all.
You need to calibrate it for the speed range, that is most important to you and accept that there may me small deviations below and above.
Use a GPS device or a smartphone app to validate GPS speed.
Compare with speedo reading and calculate the coefficient GPS divided by speedo reading.
Example : GPS 75 mph, speedo 70 mph, factor = 70/75 = 0.933
Then go to the speedo menu to show the actual wheel circumference value
Multiply this with the correction factor, enter and save the new value.
If the required value is smaller or bigger than the possible range for the radius, you need to play with the number of signals (i.e. program a higher or lower number than you actually have). In this case the entered "circumference" value has no physical relation to the real tire circumference.
Repeat GPS comparison to confirm everything is closer to where it should be.
Note that tire radius is a dependent variable. It changes under tire type/size, pressure and vehicle speed. So there is no such thing as "the radius" that you enter once and that is valid once and for all.
You need to calibrate it for the speed range, that is most important to you and accept that there may me small deviations below and above.
Bye
Martin
Martin
Re: Koso aftermarket speedo calibration problems?
Many thanks for the reply.
So for example, if the GPS reads 30 but the speedo reads 24, correction factor of 0.8.
So 1850 x 0.8 equals 1480.
Which is lower than the 1700 so invalid?
When you say signals? Are you referring to the magnets?
So for example, if the GPS reads 30 but the speedo reads 24, correction factor of 0.8.
So 1850 x 0.8 equals 1480.
Which is lower than the 1700 so invalid?
When you say signals? Are you referring to the magnets?
Re: Koso aftermarket speedo calibration problems?
If GPS is 30 and speedo shows 24, your correction must be above 1.
So it's not 0.8 but 1.25
If circumference was 1850, then the new value needs to be 2312.
If that exceeds the valid range you need to modify the number of magnets. I.e. play with the programmed number and actually installed number.
Example: If you have 6 magnets on the wheel, that's 6 signals per wheel rotation.
If you programmed 6 signals per rotation, the speedo knows you traveled the circumference when counting 6 signals.
Now if you entered 5 as the number of signals, the speedo will think the circumference is already done at 5 signals. So it "sees" a circumference that is 6/5 (or factor of 1.2) of the entered value.
With this method you "can" reach values outside the valid circumference range, but it involves quite some thinking / testing in which direction you need to change the number of signals value.
In our above example: Letting the circumference at 1850 mm and entering 5 signals will make the unit "see" a circumference of 2220 mm.
This will be close to the desired value.
If you then additionally modify the circumference to 1927 mm, you'll have the desired speed reading.
So it's not 0.8 but 1.25
If circumference was 1850, then the new value needs to be 2312.
If that exceeds the valid range you need to modify the number of magnets. I.e. play with the programmed number and actually installed number.
Example: If you have 6 magnets on the wheel, that's 6 signals per wheel rotation.
If you programmed 6 signals per rotation, the speedo knows you traveled the circumference when counting 6 signals.
Now if you entered 5 as the number of signals, the speedo will think the circumference is already done at 5 signals. So it "sees" a circumference that is 6/5 (or factor of 1.2) of the entered value.
With this method you "can" reach values outside the valid circumference range, but it involves quite some thinking / testing in which direction you need to change the number of signals value.
In our above example: Letting the circumference at 1850 mm and entering 5 signals will make the unit "see" a circumference of 2220 mm.
This will be close to the desired value.
If you then additionally modify the circumference to 1927 mm, you'll have the desired speed reading.
Bye
Martin
Martin
Re: Koso aftermarket speedo calibration problems?
Many thanks,
All makes alot more sense now,
I'll give this a try
All makes alot more sense now,
I'll give this a try