Read This! RPM, Gear, Sprockets, Tire = Actual Speed!

[FinalImpact]

I think you might have a mistake very minor though
you calculated Sidewall height to be 3.897
Sidewall Height (SH):
SH = 7.0866" X 0.55 = 3.897"

but in your formula you used 3.189. Using 3.189 should have gotten a tire diameter of 23.378 but you got the tire diameter using 3.897 which gives you a diameter of 24.8 like you calculated

Tire Diameter in Inches:
SH + SH + WD = Tire Diameter
3.189" + 3.189" + 17" = 24.8"

Oppsee - - busted a month later. . . :spank:

Kudos for catching that! :thumbup:

 

[Bates121]

Also I agree this should be a sticky or something

 

[FinalImpact]

And if you want the RPM for any given speed.....

@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@

MPH * PR * SR * G# * 1056
---------------------------- = RPM
PIE * Tire Diameter (inches)

@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@

TIRE:
Stock Tire: 180, 55 ZR17 73W
Tire Diameter: 24.8"
- - - - - - - - - - - - - - - - - - -

RATIOS:
Primary Ratio: Engine to Trans (PR): 86/44 = 1.9555
Secondary Ratio: Sprockets (SR): 46/16 = 2.8751
- - - - - - - - - - - - - - - - - - -

TRANSMISSION RATIOS: G#
G1 = 37/13 = 2.846
G2 = 37/19 = 1.947
G3 = 28/18 = 1.556
G4 = 32/24 = 1.333
G5 = 25/21 = 1.190
G6 = 26/24 = 1.083
- - - - - - - - - - - - - - - - - - -

At 25mph the RPM's are roughly -

Gear__RPM__Difference in RPM
1st = 5420
2nd = 3708 ~ 1702
3rd = 2963 ~ 745
4th = 2539 ~ 424
5th = 2266 ~ 273
6th = 2063 ~ 203
The # to the right is the difference in RPM between the selected gear above.

That's a change in RPMs of:
1st > 2nd = -32%
2nd > 3rd = -20%
3rd > 4th = -14%
4th > 5th = -11%
5th > 6th = -9%

 

[mave2911]

Ok, maybe my tach is out, or I have different ratios - but I'm seeing a complete set of different numbers.

For example, at 110kph, my tach is reading 6000rpm (ish) but that calculator has me at 85kph at 6090rpm.

I have stock sprockets, and stock tyres, so am thinking something else is wrong.

Please help!

Cheers,
Rick

EDIT: And if I enter 110kph, it says my rpm would be almost 7700?

EDIT2: Ok, ok - I'm an idiot.... Tyre diameter is greater than WHEEL diameter.....

EDIT3: I just checked my rolling circumference, 194cms, (easier to get then the diameter) and it equated to a diameter of 24.4", which throws the calculations out more! WTF?

 

[FinalImpact]

Ok, maybe my tach is out, or I have different ratios - but I'm seeing a complete set of different numbers.

For example, at 110kph, my tach is reading 6000rpm (ish) but that calculator has me at 85kph at 6090rpm.

I have stock sprockets, and stock tyres, so am thinking something else is wrong.

Please help!

Cheers,
Rick

EDIT: And if I enter 110kph, it says my rpm would be almost 7700?

EDIT2: Ok, ok - I'm an idiot.... Tyre diameter is greater than WHEEL diameter.....

EDIT3: I just checked my rolling circumference, 194cms, (easier to get then the diameter) and it equated to a diameter of 24.4", which throws the calculations out more! WTF?

PM me and I'll send you the Excel sheet I made. Sorry, no means to host it for link.

110kph = 68.4mph
@6000rpm with stock everything you should be roughly 116kph ~ 72mph!

You do have it in 6th gear yes? 5th would be 106.5kph ~ 66.2mph

As for the roll out calculation: 194cm = 76.37795in
Using 194cm as your rolling distance or 1 revolution:
5th @6000RPM =104.44kph
6th @6000RPM = 114.76kph

Let me know. . .

 

[airizzy]

So what's wrong with my bike? My rear tire has a 76.5in circumference, and when I am cruising in 6th at 75mph via GPS the rpm indicates 6900 and speedometer reads 83mph. As far as I know the gearing is stock.

 

[ChevyFazer]

Guys the stock speedo is off by 5-10% per Yamaha so nothing is a matter

 

[FinalImpact]

Gears and MPG's

Noodle on this:

At a steady 6000 RPM you get the following speed and in 60 seconds you would travel this many miles. . .

Gear - MPH - Distance
1) _ -27.68 - 0.461
2) _ -40.45 - 0.674
3) _ -50.62 - 0.844
4) _ -59.09 - 0.985
5) _ -66.19 - 1.103
6) _ -72.73 - 1.212


Obviously lingering in those lower gears hurts MPG!

My city ride home gets me high 30's low 40's. Long aggressive rides; 48 to 50 mpg.

Edit: using the stock rear tire profile.

 

[FinalImpact]

The R6 is using the the same 180/55/17 rear tire.
The primary, secondary and all 6 gears have a different ratio. It works out like so.

MPH at 6000 RPM stock gear and tires…
FZ6 - - R6
27.7 - 29.4
40.5 - 38.0
50.6 - 45.5
59.1 - 52.5
66.2 - 59.0
72.7 - 66.0

FZ6
G1 = 37/13 = 2.846
G2 = 37/19 = 1.947
G3 = 28/18 = 1.556
G4 = 32/24 = 1.333
G5 = 25/21 = 1.190
G6 = 26/24 = 1.083

Primary Ratio: Engine to Trans (PR):
86/44 = 1.95454

Secondary Ratio: Sprockets (SR):
46/16 = 2.8751


R6
1st: 31/12 (2.583)
2nd: 32/16 (2.000)
3rd: 30/18 (1.667)
4th: 26/18 (1.444)
5th: 27/21 (1.286)
6th: 23/20 (1.150)

Primary Ratio: Engine to Trans (PR):
85/41 (2.073)

Secondary Ratio: Sprockets (SR):
45/16 (2.813)

=====================================

I have an Excel sheet that crunches the numbers. Forum won't take Excel but it will take Word Docs - SO, Download and SAVE AS, Removing the ".DOC" extension LEAVING the ".XLS" extension and wallah - crunch numbers for your Tire size, SPEED, RPM, GEAR, SPROCKET Count....

Let me know if you have questions.
View attachment 48024

 

[darius]

Hey Randy. Great info!

However, what's with the pies in your numbers? Pies do slow down bikes I suppose, but I had no idea they were so critical to performance.

RPM * PIE * Tire Diameter (inches)
---------------------------------- = Speed in MPH

 

[SweaterDude]

Nice research and calculations!

I have used my GPS which is more accurate than any speedometer on any car I've used and the GPS shows my speedo to read ~7% high from 50-80 mph. Which is the way I like it....less likely to speed without knowing it!

but since you know it you can take it into account and compensate. its like setting a clock fast, if you know the difference you know the real time and arent fooled into being on time. its better if you dont know the error.

im not really trying to figure it uot in my head or anything and there's probably a reason or a canceling factor that i dont care about, but your sprocket ratio seems backwards. the front sprocket is pinion side and the rear is gear side which would make the ratio 16/46 moving from engine to wheel, not 46/16. again im not trying hard to "grade you" on this but that stuck out to me.