Author Topic: Motorcycle speed in gears  (Read 65618 times)

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Offline sofadriver

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Motorcycle speed in gears
« on: December 20, 2014, 04:30:28 AM »
Been a long time since Algebra 1.

Can anyone change this around to find speed?


            speed x 336 x pri x gear x     big   
RPM =                                            small
            -------------------------------------------
                            diameter

Thanks in advance
Mike in Tacoma

"aww, what the hell - let's just do it".............

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Online stay`tee

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Re: Motorcycle speed in gears
« Reply #1 on: December 20, 2014, 06:56:18 AM »
mph = (rpm x tyre radius) / (primary x drive x final x 168),,   8-)
First Australian to ride a motorcycle over 200mph at Bonneville,,,

Offline sofadriver

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Re: Motorcycle speed in gears
« Reply #2 on: December 20, 2014, 08:01:43 AM »
mph = (rpm x tyre radius) / (primary x drive x final x 168),,   8-)

Thanks, stay'tee.

Couldn't get that to work with the 168 (although 491mph would be coolish!).
Seems to work with 336, though.

I come up with 138mph and that works for me!
I've got more sprockets and more rpm than the figures I used.
But I'm still hoping for a little tailwind!  :-D
Mike in Tacoma

"aww, what the hell - let's just do it".............

Bike #833
100cc A/G, A/F and APS/G (in 2019)

Offline 55chevr

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Re: Motorcycle speed in gears
« Reply #3 on: December 20, 2014, 10:16:05 AM »
http://www.cosportbikeclub.org/misc/SpeedCalc.html


This is plug and play - no algebra

Offline panic

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Re: Motorcycle speed in gears
« Reply #4 on: December 20, 2014, 11:05:02 AM »
Let:
S: speed (MPH)
D1: primary drive ratio (clutch wheel ÷ motor sprocket, etc.)
D2: secondary drive ratio (rear sprocket ÷ transmission sprocket, etc.)
G: individual transmission ratio (2.50, etc.), direct drive high gear = 1.00
T: tire diameter (inches)
R: engine speed (revolutions per minute)

S = (T × R × .002975) ÷ (D1 × D2 × G)
R = (S × D1 × D2 × G) ÷ (T × .002975)
D1 = (R × T × .002975) ÷ (S × D2 × G)
D2 = (R × T × .002975) ÷ (S × D1 × G)

« Last Edit: December 20, 2014, 11:09:03 AM by panic »

Offline sofadriver

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Re: Motorcycle speed in gears
« Reply #5 on: December 20, 2014, 12:50:16 PM »
interesting.......

sta'tee's method - 138mph

55chvr's online calculator - 178mph

panic's method - 144mph

 :?
Mike in Tacoma

"aww, what the hell - let's just do it".............

Bike #833
100cc A/G, A/F and APS/G (in 2019)

Offline Stan Back

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Re: Motorcycle speed in gears
« Reply #6 on: December 20, 2014, 12:53:17 PM »
I'd use the 178 -- it's faster.  Just say it's the Exit Speed if it doesn't match your time slip.
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Offline sofadriver

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Re: Motorcycle speed in gears
« Reply #7 on: December 20, 2014, 12:58:13 PM »
I'd use the 178 -- it's faster.  Just say it's the Exit Speed if it doesn't match your time slip.

my choice, too!  :-D
Mike in Tacoma

"aww, what the hell - let's just do it".............

Bike #833
100cc A/G, A/F and APS/G (in 2019)

Offline Vinsky

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Re: Motorcycle speed in gears
« Reply #8 on: December 20, 2014, 01:24:05 PM »
Here's one that covers just about ever variation you can come up with.
http://www.rbracing-rsr.com/gearspeed.html
John

Offline Sporty Dan

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Re: Motorcycle speed in gears
« Reply #9 on: December 20, 2014, 02:13:22 PM »
Have you tried the gearing calculator that Sumner put together? It allows you change sprockets to compare in addition to transmission gears. It's down 2 threads here.

Offline panic

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Re: Motorcycle speed in gears
« Reply #10 on: December 20, 2014, 07:40:24 PM »
55chevr's page is correct - if you input your tire size and drive ratios correctly. The 178 mph result is a GIGO error.



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Re: Motorcycle speed in gears
« Reply #11 on: December 20, 2014, 09:31:48 PM »
whats a "GIGO" error,  :?,,

in relation to the formula i posted, (primary x drive x final), "drive" is the ratio of the drivin gear, eg 5th @ 1.130,, "final" is the ratio of front to rear sprocket, eg 18/42 = 2.33,,  :cheers:,,
First Australian to ride a motorcycle over 200mph at Bonneville,,,

Offline Stainless1

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Re: Motorcycle speed in gears
« Reply #12 on: December 20, 2014, 09:48:52 PM »
Garbage in garbage out...  :cheers:

Post the particulars and I'll put it thru our calculator
« Last Edit: December 20, 2014, 09:51:34 PM by Stainless1 »
Stainless
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Offline sofadriver

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Re: Motorcycle speed in gears
« Reply #13 on: December 20, 2014, 10:52:42 PM »
Garbage in garbage out...  :cheers:

Post the particulars and I'll put it thru our calculator

Thanks, Stainless.

Final drive.....3.4
1st....2.54
2nd....1.89
3rd....1.5
4th....1.25
5th....1.09
6th....0.96
front sprocket - 17. rear is 35.
tire is 23.5" (120/60-17)
13,500 rpm

I'm going to try 55chevr's calculator again, too.
« Last Edit: December 20, 2014, 10:54:41 PM by sofadriver »
Mike in Tacoma

"aww, what the hell - let's just do it".............

Bike #833
100cc A/G, A/F and APS/G (in 2019)

Offline sofadriver

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Re: Motorcycle speed in gears
« Reply #14 on: December 20, 2014, 11:07:05 PM »
duhhhhh

i was entering tire diameter where the cosportbike calculator was asking for rim diameter

i'll go stand in the corner now
Mike in Tacoma

"aww, what the hell - let's just do it".............

Bike #833
100cc A/G, A/F and APS/G (in 2019)