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post #1 of 5 (permalink) Old 03-19-2003, 10:38 AM Thread Starter
 
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Question Figuring MPH Redline Limits

OK this only involves paper and pencil...but using my gear ratio numbers and sprocket numbers - how do I figure at what speed that I'll redline (11,500rpm) in each gear without actually finding a landing strip somewhere and running the bike up in each gear.

Thanks
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post #2 of 5 (permalink) Old 03-19-2003, 03:00 PM
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Revs are reduced at 3 points between crankshaft and rear axle:
  • primary drive, a pair of gears that drives the clutch from the crank
  • transmission, 6 pairs of gears, which you select from with your left foot
  • final drive, the front and rear sprockets
First, calculate rear wheel RPM. Divide engine RPM by primary and final ratios and by the selected transmission ratio.

Next, estimate rear tire circumference from its nominal dimensions. Note that this isn't very accurate, because the nominal dimensions will vary from reality. Circumference of a 190/50 17 rear tire is:

(17 inches + (190 mm .50 25.4 mm/inch) 2) 3.14159 = 76.91 inches

Then multiply estimated circumference by rear axle RPM to get speed in inches per minute. And finally, divide speed in inches per minute by 1056 to get miles per hour.

Here are ratios I found at Honda Japan. I couldn't find them at American Honda. Verify in your owner's or service manual if possible, because I can't guarantee them.
Code:
primary: 1.520
1st:     2.692
2nd:     1.933
3rd:     1.600
4th:     1.400
5th:     1.285
6th:     1.190
final:   2.562 (41/16)
As an example, here's 2nd gear at 11,500 RPM:

axle RPM = 11500 / (1.52 * 1.933 * 2.562) = 1528

(I've substituted "*" for "" and "/" for "" in the expression to facilitate use of Microsoft's Windows calculator. Highlight from "11500" through the final equal sign, copy, and paste into the calculator.)

Now calculate speed by multiplying by tire circumference and converting to MPH:

MPH = 1528 * 76.91 / 1056 = 111
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post #3 of 5 (permalink) Old 03-20-2003, 07:46 AM Thread Starter
 
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954 MPH Redlines

Thanks Dan - The final reduction on the '02s is 2.687 (43/16)
Here's what I got

1st - 76MPH
2nd - 106MPH
3rd - 128MPH
4th - 146MPH
5th - 159MPH
6th - 172MPH

These are using Stock Michelin Pilots 190/50 zr17 on rear circ.
Hope this helps all other 954 drivers!
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post #4 of 5 (permalink) Old 03-20-2003, 11:36 AM
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Re: 954 MPH Redlines

Quote:
Originally posted by DragonFly954
Thanks Dan - The final reduction on the '02s is 2.687 (43/16)
Here's what I got

1st - 76MPH
2nd - 106MPH
3rd - 128MPH
4th - 146MPH
5th - 159MPH
6th - 172MPH

These are using Stock Michelin Pilots 190/50 zr17 on rear circ.
Hope this helps all other 954 drivers!
That looks about right. The speedo will indicate a little higher than that.

Excellent post Dan!

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post #5 of 5 (permalink) Old 03-30-2003, 08:00 PM
 
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Ok but here is a easy to do it. Email me and I'll send you a Gearing v12 exel file. then all you do is fill in all your info. You can change sprocket size and see what effect it has in all the gears and so much more.


Enjoy
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