For the gear ratio enthusiast

[1340]

Not sure if someone post this site before but its really helps you pick the right gearing for your bike. Check this out Gearing Commander: Motorcycle Speed, RPM, Chain & Sprockets Calculator Uhhh...can someone pin this?

 

[BA BUSA]

Thanks...it's been posted before
Posted via Mobile Device

 

[Poppy]

Thanks for reposting this. It's fun stuff..........

 

[x-d-x]

I have a 46t rear and according to that im losing speed in every gear all the way up? Seems odd to me. I knew i lost top end but everygear from first up????

 

[dadofthree]

It's where I always go.

 

[Goatkart]

I have a 46t rear and according to that im losing speed in every gear all the way up?

yeah...


your shortening all gear ratios when you change sprockets, not just 6th..

only way to change gearing of one gear is by getting into the transmission..


Thats why you dont put the biggest sprocket you can on the rear... you accelerate faster, but you run out of RPM range quicker too.. makes you shift sooner into next gear dropping effective mechanical advantage..


The fastest bike is the one running gearing optimised for TQ and distance covered (1/8th, 1/4, or mile)...

gearing is nothing more than a TQ multiplication effectivly...

Since torque starts falling off past its peak, the optimised shift pattern is one where you shift into the next gear, where your shift extension puts you at a higher TQ value compared to where you are...

ie, you run first gear up, at a certain point (on your dyno sheet) tq starts falling off, so you need to shift into second to keep accelerating, so you look at second gear, find out what minimum rpm you need to be at, such that your gearing gives you more TQ to the tire than your getting in first...

You can model your torque output vs gearing to get an ideal shift map pretty easily actually..

or for the average setup, coincidently, it ends up being that shifting at around 500-800 rpm past peak HP is the ideal shift point...


its all about shift extension, and race teams spend a lot of time trying to get just the right gearing for their setups...

 

[Spkrdctr]

I use it all the time. That was how I picked my 19 tooth front and 40 tooth rear. Works perfectly. No reason to be running down the highway at a high rpm. Although even with my two sprocket changes it only affects top speed rpm by about 400 rpm I seem to recall. I do know my fifth gear is what used to be sixth. Anyway, Gearing Commander is fun to play with.