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View Full Version : Rear sprocket effects on the computer and or speedometer...



buell-fan
09-16-2015, 01:29 PM
Please explain how changing the rear sprocket effects the stock computer and or the speedometer. What effects would there be with one of the programmable ecm's?

kneepucker
09-16-2015, 05:23 PM
http://www.jtsprockets.com/fileadmin/files/jtgearratio.pdf

:cheers:

mackja
09-16-2015, 06:55 PM
Another really cool site to see how gearing, tire size, engine speed and mph is,
http://www.gearingcommander.com/ I can play on this site for hours.

buell-fan
09-16-2015, 07:29 PM
The gearing ratios and speed charts are cool. I do study them, and thanks for posting them. But what I was wondering about was how the ratio change actually effects the speedometer accuracy and whether the ratio change somehow effects either a stock or programmable ecm specifically. I ask this because I read where an ebrforum member's ecm says he is in a lower gear than he actually is in. He had a 44 tooth rear sprocket I think. If it does this then it must do other things to the bikes computer' like effect speed readings and such.

dmhines
09-18-2015, 12:54 PM
The speedometer and gear indicator will not be 100% accurate.

zac4mac
09-19-2015, 12:54 PM
Just an observation, at the Colorado Mile, I got to see indicated vs. timed.
At 172.4 timed I saw 174 on the speedo of my RS.
The mobile radar signs my speed is always spot-on but that's around 45-50mph...

Z

buell-fan
09-19-2015, 01:46 PM
Good to know Z. As far as changing calibrations go, Dean Adams informed me that in the race ecm you can change the speedo and gear indicator to be correct based on which gear you have on the back.