IMPORTANT: Since the TDB will not accept uploaded xls files I changed the file type to doc. Save the file to your desktop or folder of choice, then change the file type to xls before you open it. I've tested this, and it works.
The attached file can be used to play with different gearing combinations and tire revs/mile after you change the file type to xls, and, of course, you must have Excel on your computer.
Inputs are tire revs/mile, axle (final drive) ratio, gearbox ratios, and maximum revs in each gear.
Outputs are intergear ratio, speed in each gear at max revs, revs in the next gear at the shift point, and top gear revs @ 60 MPH.
Manufacturers' and tire retailers web sites' technical data usually include revs/mile for most make/model tires. If you can't find your exact tire, use a spec from another make/model of the same size. Racing tires usually don't quote revs/mile, but they do quote inflated OD or you can measure the circumference. Compute the rolling circumference, in feet, using 97% of the specified inflated OD (to account for deflection) or 97% of your measured circumference. This value divided into 5280 is revs/mile and should be very close. For a typical road tire with 10 to 12/32s new tread depth, revs/mile will increase about 2 percent when the tread is down to the wear bars.
The chart can accomodate six cases, and you can repeat the cells if you want more. Just replace the numbers in the input cell variables stated above with your data.
After considerable hacking I was able to get Excel to plot the lines of speed vs. revs for each gear, but it's been awhile, so don't ask me how I did it. The chart was done with an older version of Excel that was part of Office 2000.
If you have any questions or comments, place then here so everyone can see.
Duke
The attached file can be used to play with different gearing combinations and tire revs/mile after you change the file type to xls, and, of course, you must have Excel on your computer.
Inputs are tire revs/mile, axle (final drive) ratio, gearbox ratios, and maximum revs in each gear.
Outputs are intergear ratio, speed in each gear at max revs, revs in the next gear at the shift point, and top gear revs @ 60 MPH.
Manufacturers' and tire retailers web sites' technical data usually include revs/mile for most make/model tires. If you can't find your exact tire, use a spec from another make/model of the same size. Racing tires usually don't quote revs/mile, but they do quote inflated OD or you can measure the circumference. Compute the rolling circumference, in feet, using 97% of the specified inflated OD (to account for deflection) or 97% of your measured circumference. This value divided into 5280 is revs/mile and should be very close. For a typical road tire with 10 to 12/32s new tread depth, revs/mile will increase about 2 percent when the tread is down to the wear bars.
The chart can accomodate six cases, and you can repeat the cells if you want more. Just replace the numbers in the input cell variables stated above with your data.
After considerable hacking I was able to get Excel to plot the lines of speed vs. revs for each gear, but it's been awhile, so don't ask me how I did it. The chart was done with an older version of Excel that was part of Office 2000.
If you have any questions or comments, place then here so everyone can see.
Duke
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