I wrote a small program back in 1996 that will help you find the proper Gear Ratio for your car when you go racing. Not only does it help you when you go to a new track, but can help compensate for tire wear and/or new tires.

You can find out more about it here and download the latest version. Don't worry, it won't cost you a cent, it's free!

Have you ever noticed that the more you run your car that the slower it seems to go? Even if you rebuild the motor it just doesn't seem to perform as good as it did before? Then it might just be your tires!

That's right, as your tires wear down, your car's top speed also drops. Let me show you what really happens. We will take a hypothetical setup were the original tire size is 2.5 inches and a 5.0:1 gear ratio. For every revolution the motor makes, your cars moves forward 1.570 inches. This 1.570 figure is called the inch/gear, some call it roll-out.

Now, lets take the same 5.0:1 gear ratio with tires that have worn down to 2.3 inches. The inch/gear now comes out to 1.444 inches, almost 10% less then before! This can create a big difference on the track. You also need to pay attention to this when you put on new tires as the larger tires will mean you need to adjust your gear ratio again.

You can now easily see how tire size effects your cars performance. To bring your car back up to "like new" performance, you need to adjust your gear ratio to 4.6:1. You can manually figure out your inch/gear by using the formula of (TireDia. x 3.14)/GearRatio = InchGear or you can download the Gear Finder program (attached below) that not only will figure out inch/gear and the related gear ratio and tire size, but how many laps your car should run if you have a dyno reading for your motor.

Check out the screen shot to see everything the Gear Helper program has to offer.

Save the Gear Finder file you download to a directory or folder on your computer. Just double-click the gearfinder.exe file to extract all of the Gear Finder program files. Read the README.TXT file for the latest information on the Gear Finder program and read the GEARHELP.TXT file on how to use the Gear Finder program.

By using this method, you can now go smoke 'em next weekend!

WHAT'S THIS ABOUT MOTOR RPM?
This is a formula that I have used for quite a few years. You need to find out the "loaded" RPM of your motors using either a Vantage or Competition Engineering dyno. You should test Stock motors at 6.7 volts with a 20 Amp draw. Modified motors should be tested at 6.5 volts with a 27 Amp draw. Take the RPMs you get from the above tests, subtract 10% from the value (a 12000 RPM motor would become 10800), and enter that into the RPM text box. If you have entered your Tire Diameter, Gear Ratio and Track Length (actual driving line), you will have a very good idea of how many laps you should get.

How is this helpful? The formulas can also be worked out other ways. If you know your Motor RPM, Tire Size, Track Length and Lap Record, you can work backwards to find out what Gear Ratio you need to run to be close to the track record. It may not sound like all of this would even be close to real life, but I have found that I have normally been within on tooth on my pinion gear size when using this method. Just play around with it, punch in the numbers for the equipment you have and see how close the answers are. You may need to fudge a little on the RPM percentage according to your style, but once you find that correction factor, it will hold true the vast majority of the time.
USING R/C GEAR FINDER

* Finding the all-important inch/gear value
First pick the measurement system you are using. Select English for use in the U.S., Metric for the rest of the world!
* Enter the size of your pinion gear, spur gear and tire diameter. Also enter the ratio of your gear box if you have one. An example of this would be to enter 2.85 if your gear box has a reduction of 2.85 to 1.
* Click on the SOLVE (Labeled F3) button next to the box labeled GEAR RATIO that has the lines attached to it from the SPUR and PINION areas. This gives you your Gear Ratio.
* Now, click on the SOLVE button next to the text box labeled INCH/GEAR. (Labeled F6) This gives you your Inch/Gear size.
* FINDING NUMBER OF LAPS
Now if know the Track Length (driving line) and your Loaded Motor RPM you can enter these items and find out how many laps you should be able to turn.

DESCRIPTION AREA

* An area has been added so you may enter a description for the figures you have entered. This info is saved along with all of the numbers you have entered.

ERROR CODES

* All of the SOLVE buttons when clicked check to see if the proper values are entered in the proper places. If values are missing or are out of a normal range, you will also be notified. Just click OK in the error box and your cursor will be in the proper text box for you to correct the error.

* If you get a Run Time error when trying to run the program, download and install the vbrun file attached below. This will install the required runtime files.

End of article. Your comments are welcome.

Thanks you very much !

It easier now !!

Pierre

What is a vantage dyno??? the only vantage dyno I kknow of is the peak racing one...and I dont see a way to load something to 26 amps... Just curious>>>I dont have the $$$$$$ for a ce dyno right now..

I like the software.. Thats nicer than bringing charts and calculators to the track.. ;)

hank, is there away to update the pinion and spur gear charts. your pinion list goes to 51 and i have up to a 60 tooth pinion. i dontk now if theres bigger or smaller spurs that what u have listed.

The Vantage dyno (no longer made) is a load dyno simular to the CE dyno. But instead of programming in the loads you had to manually set them by turning a load knob.

Really, the only good dyno is a load dyno. You should still be able to use the GearFinder if you compare a known good motor.

The program was made almost 10 years ago. I no longer have the source code so can not make any changes to it.... sorry.

No need to be sorry>>actuallly I was glad to see it... I had a similar program for a tekin dyno...when used correctly on a properly set up car you were on record pace almost everywhere you went...I was looking for a more modern version..well more modern than 1991 anyway... Now I guess I need to loook for a ce dyno..

here is one also...
http://www.teamassociated.com/racerhub/techhelp/marc/gearform.html

Ok, so how do i get this to work on WinXP??

Thanks,
FreaK

If anyone using this program has a AUTOEXEC file error,try this link. You must extract it to your system32 folder.

http://forum.iamnotageek.com/attachment.php?attachmentid=18265

This is the page i got it from....
http://articles.networktechs.com/413-p1.php

Ok, now that i am playing with this program, several questions...

1) Is this program based on a 4min race time?

2) If running a 4 cell, should i calculate RPM load at voltage the pack is putting out?

3) And where is the suite of programs that work together????? 8) LOL

Good Job Hank!!

If you are getting a Run Time error, download and install the vbrun301 file attached to the 2nd message.

I am having trouble installing is there another way toi download it? Gear Finder
Big Papa

Hankster,

Do you know how to do this? I need 48 pitch to 64 pitch spur gear conversion formula. Thanks Tam

Spur conversion from 48 to 64: take your 48 pitch spur divide by 1.5 then muliply by 2. For example 81tooth divided by 1.5 = 54 then multiply 54 by 2 equal 108. So an 81spur (48pitch) is equal to a 108spur (64 pitch)

so do you do the same thing for pinion