Sprocket availability

[mzterg]

  I always enjoy RoryD's post.  So informative and he's not afraid to experiment 

Prepare to be bored 

Standard gearing is 14/46 = 3.285.

7000rpm is 60mph on my speedo.  I want to have the same speed at 6000rpm instead of 7000 rpm.

Therefore:

7000/3.285 * x = 60 (where x is a constant fudge factor which takes into account all the non-variables
like wheel/tyre size etc.

so x = 60 * 3.285/7000 = 0.028

Now we can calculate anything we like. 

Take standard gearing 7000/3.285 * 0.028 = 60mph (we already know that!)

Or RoryDs original gearing 15/46 = 3.067, so 7000/3.067 * 0.028 = 64mph at the same revs - 4mph
more than standard. Not bad.  Many people on the forum are happy with that gearing. 

But I want more.  16/45 = 2.8125, so 7000/2.81 * 0.028 = 70mph i.e 10mph more at 7000rpm. 

So at 60mph, 60 = rpm/2.81 * 0.028, so rpm = 60 * 2.81/0.028 = 6021 rpm.  Near enough to 6000 at 60mph.   
So the magic ratio is ~2.81.  You can do it with a 16t front and 45t rear, or 15t front and 42t rear,
or 14t front and 40t rear.  RoryD's latest ratio is approaching the magic figure 14/41 = 2.92.   

There are many ways to skin a cat but I think you could do 16t front, 45t rear, no change to chain length and
still get usable relaxed gearing.

Thats all folks. 

[Kantara]

confused, well yes.  I will stick to my 15t front and bog standard back sprocket.

Good to have you back mate.

[mzterg]

Thanks Kantara.  Nice to see you are still the heart and soul of the group 

Keep on posting my friend 

[mzterg]

Hi Folks 

Old thread, but does anyone know the front sprocket size used on the new GSXR250 or V-Storm 250.  Are they still using the 14t front sprocket as used on the Inazuma, or did they go for a more useable 15t sprocket.  I have had a hunt around the internet for info on the new bikes, but they are too new for anyone to bother posting about yet.

Just wondering if there is an easier source of replacement sprockets for the Inazuma.

Thank you