Motorcycle speed in gears

[sofadriver]

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

[stay`tee]

mph = (rpm x tyre radius) / (primary x drive x final x 168),,   8-)

[sofadriver]

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! 

[55chevr]

http://www.cosportbikeclub.org/misc/SpeedCalc.html


This is plug and play - no algebra

[panic]

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)

[sofadriver]

interesting.......

sta'tee's method - 138mph

55chvr's online calculator - 178mph

panic's method - 144mph

[Stan Back]

I'd use the 178 -- it's faster.  Just say it's the Exit Speed if it doesn't match your time slip.

[sofadriver]

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! 

[Vinsky]

Here's one that covers just about ever variation you can come up with.
http://www.rbracing-rsr.com/gearspeed.html

[Sporty Dan]

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.

[panic]

55chevr's page is correct - if you input your tire size and drive ratios correctly. The 178 mph result is a GIGO error.

[stay`tee]

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,,  ,,

[Stainless1]

Garbage in garbage out...  

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

[sofadriver]

Garbage in garbage out...  

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.

[sofadriver]

duhhhhh

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

i'll go stand in the corner now