# True speed per 1000 revs calculation helper

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Something I did to quickly work out true speed in each gear  _ this is for gsxr1100 k-n and b1200

Quick calculation helper numbers.

1st gear  0.25381

2nd gear 0.37099

3rd gear 0.4841

4th gear 0.58182

5th gear 0.66275

Then measure rear wheel circumference in inches - you multiply with this number.

work out final gear ratio, you divide the number by this. This give mph per 1000 rpm.

Often used final gears and ratios

14 : 48 = 3.43

15 : 48 = 3.2

15 : 47 = 3.1333

15 : 46 = 3.0667

15 : 45 = 3

Here's 4th gear speed for my bike for example.

0.58182 ÷ 3.0667 × 79.5 inches = 15.08 mph per 1000 revs

For 5th

0.66275 ÷ 3.0667 × 79.5 = 17.18 mph per 1000 rpm

All I did was work out most of the calculation minus final drive and tyre circumference , I just like working things out .... hopefully someone will find it useful too.

my brain's just leaked out of my ears  I hate numbers !!!

32 minutes ago, Oilyspanner said:

Something I did to quickly work out true speed in each gear  _ this is for gsxr1100 k-n and b1200

Quick calculation helper numbers.

1st gear  0.25381

2nd gear 0.37099

3rd gear 0.4841

4th gear 0.58182

5th gear 0.66275

Then measure rear wheel circumference in inches - you multiply with this number.

work out final gear ratio, you divide the number by this. This give mph per 1000 rpm.

Often used final gears and ratios

14 : 48 = 3.43

15 : 48 = 3.2

15 : 47 = 3.1333

15 : 46 = 3.0667

15 : 45 = 3

Here's 4th gear speed for my bike for example.

0.58182 ÷ 3.0667 × 79.5 inches = 15.08 mph per 1000 revs

For 5th

0.66275 ÷ 3.0667 × 79.5 = 17.18 mph per 1000 rpm

All I did was work out most of the calculation minus final drive and tyre circumference , I just like working things out .... hopefully someone will find it useful too.

Or just let gearing comander work it out for you

I wanted to know how to work it out, so I could understand it myself ......my wife's a maths teacher too, there's no hope !

I still do not understand how you get from gear ratios, final drive reductions and the circumferance of the tyre in inches to mph per 1000 revs without including figures for the primary drive reduction and a conversion of inches into miles .

1 hour ago, Dezza said:

I still do not understand how you get from gear ratios, final drive reductions and the circumferance of the tyre in inches to mph per 1000 revs without including figures for the primary drive reduction and a conversion of inches into miles .

Are you a maths teacher Dezza?

No

I was really bored.

Now get it to factor in drag and it'd be really useful.

1 hour ago, Gixer1460 said:

Now get it to factor in drag and it'd be really useful.

@Gixer1460You mean the Lilly Savage factor ?

5 hours ago, Gixer1460 said:

Now get it to factor in drag and it'd be really useful.

Yeah like those chavs who test top speed of their Golf GTIs on dynos haha

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