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February 3rd, 2006, 08:51 PM  #1 
Covered in mud...

A nice gear chart calculator I made...
Its in Excel format.
I have created tabs with many of the common transmissions and transfer case gear ratios, and tire sizes (you need to enter tires as revs/mile) Sure, there are online calculators. I like this because I can copy them and make a tab for each vehicle, or possible vehicle configuration. Just type in your specifics in the white boxes and its all set. Enjoy! http://www.lordsofevolution.com/hagg.../gearchart.xls 
February 22nd, 2006, 09:58 PM  #5 
Covered in mud...

Its always tough to find them for big sizes. Up to 35" I have taken them from manufacturers like BF Goodrich, etc, who publish the sizes.
Above that, the sizes really start getting somewhat different from the sidewalls anyway, so those are pretty close approximations. If you want to calculate a tire's revs per mile its this: 5280 feet  Tire Circumference Although, tire circumference isn't exactly the right term, since the tire bulges and has a lower effective rolling radius. So you calculate the circumference using the rolling radius. Example: If you have a 31" x 10.5" BFG AT on an 8" rim, it has a true rolling radius of 1.245 feet (14.94 inches). So the radius is 1.245 x 2 x 3.14159 = 7.82 feet. Every rotation, therefore, will drive you forward 7.82 feet. 5280 / 7.82 = 675 rotations per mile. So, if you went out and measured, say, a 49" IROCK, and it had a loaded radius of 23.5", then it would have a circumference of 12.30 feet. And would have approx 429 revolutions per mile. 
April 4th, 2006, 09:06 AM  #6 
Me balls are huge

Here's the formula for using excel to calculate revs per mile:
=20852*((C2/2+((A2/25.4)*B2/100))*2)^(1.0003) Copy and paste the above formula into cell D2. Then enter tire width into cell A2, aspect ratio into cell B2, and wheel diameter in cell C2. In case your real dumb: Example LT305/70/R16 305 is the tire width in millimeters 70 is the aspect ration (sidewall height is 70% of tire width) 16 is the wheel diameter in inches Haggar, you might want to add this to your revs per mile tab. 
April 4th, 2006, 09:22 AM  #7  
Covered in mud...

Quote:
For example, when you look at car tires (I use this for looking at car situations, too, for cruising and racing), they are very very close to accurate, usually about 1%2% smaller than advertised. Then smallish truck tires like 31s or 265/75R16s have maybe 34% smaller. Once you get up to big sizes, then its all out the window. A 35" SSR is a full 1.5" taller than a 35" Bogger, so you just need to figure whats best for your tire. That, plus most people aren't running metric tires. 

May 31st, 2006, 07:38 AM  #8  
Simplify...

Quote:
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May 31st, 2006, 07:47 AM  #9 
Covered in mud...

Thanks!
Feel free to make suggestions/corrections/improvements.. I have some wierdly modified versions for cars where I put in a powerbard, and can see wheel torque output from 5 to 100 mph. More of a carr racing mod, though, and its mostly manually edited.. 
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