Motorcycle Gear Calculator

[landracing]

Here is a gear calculator for motorcycles, Have never tried to input for a car.

[narider]

Note: To measure tire circumference roll bike and measure the length of one revolution of rear wheel. Then divide measurement by 3.1416 to calculate diameter.

I've gotten much better acuracy by measuring from the axle centerline to the bench with the bike loaded to get diameter as it takes the weight as well as the air pressure into effect. Then in a calc like this, multiply that number by 3.1416 to get the required circumfrence.
I've even gone as far as measuring my suspension travel in play, and then strap the bike down on the lift to that suspension compression and measure the tire there... the difference was minimal but was more accurate in the end result.
Todd

[Stainless1]

Todd, thinking a spinning tire grows a little, and compressed radius might short ya a little, but make up for some of the slip at Bonneville... 

[ol38y]

http://www.rbracing-rsr.com/gearspeed.html

I've used this one for Harleys and it's been right on.

Larry

Oh yeah. I couldn't open Jon's for some reason.

[narider]

Good point,
I don't agree that ALL tires grow though, the numbers show the oppositte sometimes(at least on our slow bike - lol). Deb's bike is in the "actual diameter" group while mine is in the "reduce diameter" group.

I just use numbers that I can justify a reason for and are repeatable and accurate with the tower numbers(no matter how I come up with them, though the axle down measurement seems the best overall and most accurate for me so far).

The suspension travel I'm refering to, is referenced at the traps. This is the closest that our calc that Deb and I made comes. We figured in a tire wear & tire growth area also(can be used to compensate for tire or even clutch slippage as well).
Todd

[narider]

Todd, thinking a spinning tire grows a little,

I don't agree that ALL tires grow though, the numbers show the oppositte sometimes(at least on our slow bike - lol).

Maybe I should retract that until my bike's actually able to spin the tire 
Todd

[Peter Jack]

Larry:

It probably won't load if you don't have MS Excel loaded on your computer.

Pete

[Uncle Jimbo]

Thanks for the Gear calculator chart Jon. It downloaded ok for me but I have a quick question for anybody. The illustration showed an 18 tooth drive sprocket on all the examples. We are running a 22 tooth on the drive side and are playing with a 40 - 38 - & a 36 on the rear that we have sitting on the bench. My question would be.  What would the actual formula be for calculating different sprocket combinations. I can see where this would help save time and engine ware from experimenting without the formula.
Respectfully
Uncle Jimbo

[Peter Jack]

In the upper left hand corner of the chart change 18 to 22 and everything happens!

Pete

[panic]

For those not familiar with Excel, what's nice is if you put the cursor in a cell watch the command line. If numerical data appears, you can change it and watch all new results appear all over the table automatically (if a formula shows, leave it alone!).
I color-code the font in my charts to indicate which is the "master cell", where input is variable - the "slave cells" will reproduce this without prompting, and are colored differently. Output values are also coded for easy recognition.

[panic]

Here's one for the common H-D big twin 4 & 5 speed boxes that just does RPM drops on shifting, with the correct tooth counts already input (10 ratio choices).
Shows % gained & lost on upshift, new RPM after shift, and lowest RPM reached on full upshift.

[landracing]

I will re-format the sheet to show color coded user input fields. Usually I do that anyways but this one it was not done.

Jon

[panic]

Warning: on my downloadable .xls you can input new tooth counts in Columns B & C (even though they're not coded as variable), but only if the transmission is "conventional" where the high gear is locked to the output shaft (direct) in high gear. All-indirect transmissions will need some adjustment to get good output.
If you're trying to make a new one and have trouble, e-mail me I might be able to sort it out.

[Uncle Jimbo]

Thanks Pete !  That is way cool, I would never have thought to try that. I am a bit of a cyber neanderthal, and not afraid to admit it. Now to get the printer warmed up and make a few different calculations.
Thanks again.
Uncle jimbo

[panic]

Added primary drive ratio, front and rear sprockets, tire OD, and speed in MPH in each gear to the download file (above).
If you already got one, just download again and it will replace the older file.