Formula for calculating speed with different sprocket sizes.

This is a discussion on Formula for calculating speed with different sprocket sizes. within the Z1K/Z750 Performance Upgrades forums, part of the Kawasaki Z1000, Ninja 1000, Z750 & Z-750S category; If you want to see how a sprocket change affects your speed vs. RPM the formula is as follows;
Speed in MPH=RPMxFSTxTCMM, divided by PGRxGRxRSTx26817.
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Formula for calculating speed with different sprocket sizes.

If you want to see how a sprocket change affects your speed vs. RPM the formula is as follows;
Speed in MPH=RPMxFSTxTCMM, divided by PGRxGRxRSTx26817.
RPM=engine RPM
FST=front sprocket teeth, (15,16 or whatever)
TCMM=tire circumference in milimeters, (a 190 50 zr17 is about 1975mm)
PGR=primary gear ratio, (Z1000 2003-2006 is 1.714)
GR=gear ratio, (What gear your in ratio, Z1000 1st=2.571 2nd=1.941 3rd=1.555 4th=1.333 5th=1.200 6th=1.095, 2003-2006) choose one only.
RST=rear sprocket teeth
26817=26817 the number to convert from circunference in mm to MPH.
So with a 16 tooth front and a 42 tooth rear in 6th gear at 11,000 RPM your speed would be 164 MPH. with a 15 tooth front retaining the 42 rear your top speed in 6th at 11,000 RPM would be 154 MPH.
I hope this helps.

I have an excel spreadsheet for the speed calulations that may be a bit different then Firehawks if you want I can email it to whoever wants it. I went to the link Firehawk provided but I could'nt download it due to the firewall here. I have attached a jpg that shows my spreadsheet output format. On my spreadsheet you enter in RPM and tire size (you can also change rear ratio but the default is stock 42/16) and the spreadsheet calculates the rest for each gear 1 thru 6 but it will not work on anything except a Z1000 since the transmission ratios are locked.

INTHERED

Last edited by INTHERED; 05-19-08 at 11:48 AM.

2009 ORANGE/BLACK HD XR1200
2008 ORANGE/BLACK KTM 990 SUPERDUKE, Akrapovic Slipons
2008 ORANGE/BLACK HD FXDL, Vance & Hines Slipons, XIEDs, SE Heavy Breather AC
SOLD! 2003 ORANGE Z1000, Yosh Slipons, PCIII, K&N w/stage 2 airbox

That link works.
Now I wish I had'nt of wasted my time making my spreadsheet.
I really like the section on determining chain length when changing sprockets.

INTHERED

2009 ORANGE/BLACK HD XR1200
2008 ORANGE/BLACK KTM 990 SUPERDUKE, Akrapovic Slipons
2008 ORANGE/BLACK HD FXDL, Vance & Hines Slipons, XIEDs, SE Heavy Breather AC
SOLD! 2003 ORANGE Z1000, Yosh Slipons, PCIII, K&N w/stage 2 airbox

Helped me decide on -1/+2 conversion... I was a bit concerned that my cruising rpm would be higher - but it's not that significant... And I get to use the same chain :-D

Why make it so complicated ? All you need is a base point. Let us say 16/42 is 4krpm at 60mph. 42 divided by 16 is 2.625 and 42 divided by 15 is 2.8 2.635 divided by 2.8 is .9375 and .9375 times 60 is 56.25 so lowering one tooth in this case changes 4k at 60mph to 56 mph. Anyone but me understand this ?

It is better to remain silent and be thought of as a fool,then to open your mouth and remove all doubt. Abraham Lincoln.

Why make it so complicated ? All you need is a base point. Let us say 16/42 is 4krpm at 60mph. 42 divided by 16 is 2.625 and 42 divided by 15 is 2.8 2.635 divided by 2.8 is .9375 and .9375 times 60 is 56.25 so lowering one tooth in this case changes 4k at 60mph to 56 mph. Anyone but me understand this ?

Yes but people are to lazy to do any calculations. A real human will use a formula and do it on paper not with a calculator. I think that is one of the reasons we are all f****d.