SV Gear/Sprocket Ratio calculator

Right, I have posted this in response to what was being said in another thread, but as I’d like to think it was use to many, I have made this new thread.

A bit of background:-

I generated a bit of software for myself so I could easily see the effects of changing sprockets. Using the engine revs, wheel circumference and gear ratios, I could mathematically calculate the theoretical speeds in each gear with different gear ratios/sprocket combinations. It was actually based around my R6 racebike; as base setting sprocket combinations is always a bit of a head scratcher.

But as I now have an SV too (roadbike) and was thinking of fitting a 14t front sprocket, I updated the software with the ratios for my ‘curvys’ ‘box.

Anyway, down to business

There are 3 files available, GearRatioCalculator_SV650.exe, GearRatioCalculator_SV1000.exe and COMDLG32.OCX.

Basically I have looked up the gearbox ratios for both the SV650 (all years) and the SV1000 (for the 1000cc impostors amongst us ) and generated two separate executables using this data. No prizes for guessing which file is for which bike!!

Copy whichever bike you are interested ins calculator to your pc. Some of you will also need the .OCX file too (for the dialog boxes) so save this to the same folder too. Then, well fire up the GearRatioCalculator and enjoy

Here is the URL for the files/folder (that Carsick from here has hosted for me):-

http://bikes.carsick.me.uk/GearRatioCalc/

If anyone has any questions or not sure what to do, then just shout

I did write this for myself and I am not a software engineer by trade, so if you don’t like the colour scheme or summin, well I don’t care but if there is any constructive criticism, I’d be happy to hear it.

Oh and as with all good software realises I better give a short disclaimer … … I am sure there is proper legal jargon, but basically … don’t come crying to me (or to me via your lawyer)!!!

Very cool

nice! thanks!

Would be good idea to make this a sticky and also put it on the main site.


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Oh and I should point out the default circumference of 200cm is just that (a default). 200cm won’t be far off, but if you want to make the results more accurate, then you should measure the circumference of your rear tyre. Mine is actually 199cm, the one I took off recently (as it was worn out and a completely different make model anyway) was 196cm. You can measure your own and change this value from default at runtime yourself.

Anyone got the gearbox ratios for another bike they want a calculator for???

This is also useful if you want to know what sprocket combo to use if you say lower your bikes rpm at 70mph by 500rpm as you do lots of motorway riding.

i.e. Standard SVS sprockets (15f 44r) will see you 70mph at about 4900rpm in top. If you wanted to drop that 500rpm to make it 70mph at 4400rpm, you would need to either fit a 17t front or a 40 rear. Or perhaps a 16t front, 42 rear would be a more logical choice. You can fiddle to your hearts content

You will also see that putting a 14t front on will only reduce theoretical top end by 10mph and still (theoretically) allow about 140mph at 10500rpm (the red line)!!

You will also see that when your mate says he can get 160mph out of his SVS with standard gearing he is full of it as it is not mathematically possible!!!!!

I say theoretically as a few factors need to be considered … at speed the tyre will expand, therefore changing the circumference. You will also get some degree of clutch slip, finally although theoretically with a 17t front 40r your bike would be geared to do ~187mph at the redline it is very unlikely that it will pull all the way to the line with that gearing!!! Still fun/interesting to do the calculations though

Originally Posted by Blue_SV650S

Oh and I should point out the default circumference of 200cm is just that (a default). 200cm won’t be far off, but if you want to make the results more accurate, then you should measure the circumference of your rear tyre. Mine is actually 199cm, the one I took off recently (as it was worn out and a completely different make model anyway) was 196cm. You can measure your own and change this value from default at runtime yourself.

Anyone got the gearbox ratios for another bike they want a calculator for???

This is also useful if you want to know what sprocket combo to use if you say lower your bikes rpm at 70mph by 500rpm as you do lots of motorway riding.

i.e. Standard SVS sprockets (15f 44r) will see you 70mph at about 4900rpm in top. If you wanted to drop that 500rpm to make it 70mph at 4400rpm, you would need to either fit a 17t front or a 40 rear. Or perhaps a 16t front, 42 rear would be a more logical choice. You can fiddle to your hearts content

You will also see that putting a 14t front on will only reduce theoretical top end by 10mph and still (theoretically) allow about 140mph at 10500rpm (the red line)!!

Yuo will also see that when your mate says he can get 160mph out of his SVS with standard gearing he is full of it!!!

I say theoretically as a few factors need to be considered … at speed the tyre will expand, therefore changing the circumference. You will also get some degree of clutch slip, finally although theoretically with a 17t front 40r your bike would be geared to do ~187mph at the redline it is very unlikely that it will pull all the way to the line with that gearing!!! Still fun/interesting to do the calculations though

Sounds good, but does it tell you how many links you'll need in the chain too? :P

Originally Posted by chazzyb

Sounds good, but does it tell you how many links you'll need in the chain too? :P

Would you like me to make it physically change the sprockets for you too??? ... or perhaps make you a cuppa?!?

I am sure if you showed this to a lass it would get you laid?!?!?

Seriously though, depending on the wear/adjustment in your chain, you will probably get away with 1 or 2 teeth with the same chain, else logically you need to make it 1 link more for every tooth you go up, or 1 link less for every tooth you go down!!