Backwards Math

[Robby]

I had my 2007 RSV triked (yeah I know, I really had no choice) and because I always thought the gearing was too tall I ordered a higher numerically final drive.

It is a Hannigan and the stock differential ratio is 2.73:1 and I thought I was ordering 3.08:1. Now I am informed that it is 3.73:1, which I do not think it is.

So I endeavored to do the reverse math and would like for someone to verify my figures.

 

Tires 205/65R-16. Google says 785 revolutions per mile. I measured circumference and I get 761 per mile so used higher number.

 

785 x 3.73 x 0.786 (5th gear ratio) x 1.776 (primary reduction) = 4087 RPM at 60 MPH

 

Am I missing anything????

 

I purchased a cheapo (wire wrapped around spark plug wire) tachometer. It does not agree, nor does my ear.

Hannigan does use the 3.08:1 on Honda,s and if I use that number the tachometer and my ear agree.

 

785 x 3.08 x 0.786 x 1.776 = 3375 RPM at 60 MPH.

 

I think they used the 3.08 by error but bike runs just fine and with the extra weight, kit adds 320 lbs. to total, more power, less speed is just fine.

 

Am I doing the math correctly????

 

Oh, last but not least, I have all the stuff from conversion including a Hagen shock. Everything has about 25000 kilometers except shock and it maybe 5000 kilometers. You can have it all, free, but you have to come and get!

[cecdoo]

Would be interested in buying the hard bags from you if you are interested in shipping them. I also have an 07 Hannigan, mine has the inverted ford rear. Gearing seems fine although I dont come out of 4th till about 70mph.

 

Craig

[WildBill1]

I had my 2007 RSV triked (yeah I know, I really had no choice) and because I always thought the gearing was too tall I ordered a higher numerically final drive.

It is a Hannigan and the stock differential ratio is 2.73:1 and I thought I was ordering 3.08:1. Now I am informed that it is 3.73:1, which I do not think it is.

So I endeavored to do the reverse math and would like for someone to verify my figures.

 

Tires 205/65R-16. Google says 785 revolutions per mile. I measured circumference and I get 761 per mile so used higher number.

 

785 x 3.73 x 0.786 (5th gear ratio) x 1.776 (primary reduction) = 4087 RPM at 60 MPH

 

Am I missing anything????

 

I purchased a cheapo (wire wrapped around spark plug wire) tachometer. It does not agree, nor does my ear.

Hannigan does use the 3.08:1 on Honda,s and if I use that number the tachometer and my ear agree.

 

785 x 3.08 x 0.786 x 1.776 = 3375 RPM at 60 MPH.

 

I think they used the 3.08 by error but bike runs just fine and with the extra weight, kit adds 320 lbs. to total, more power, less speed is just fine.

 

Am I doing the math correctly????

 

Oh, last but not least, I have all the stuff from conversion including a Hagen shock. Everything has about 25000 kilometers except shock and it maybe 5000 kilometers. You can have it all, free, but you have to come and get!

 

You're spot on with your calculations also believe the Honda 3.08 was used in your installation.

[Robby]

I forgot, in USA Independence Day. Have a great day!