Changing sprockets / gearing

[ELIMINATOR]

http://www.gearingcommander.com/

Having spent quite a few minutes playing with the above gear calculator.

Has anyone changed their gearing from standard? When my chain is due for replacement, I am quite tempted to change the gearing for better fuel economy.

So it revs less for any given speed, but, will lose out on acceleration.

Anyone care to give their thoughts?

If I were to change to a 19/38 from 17/40 then at 90mph the rpm drops to 4641, as opposed to the current 5460.

Will this reflect in the fuel consumption? Or isn't it quite that simple?

http://www.motorcycleanchor.com/motorcycle/how_to/mc_sprocketmath.html Aha, as I thought it is perhaps too big a change.

 

[uncle dick]

As long as the engine is reasonably within its powerband when you're riding normally you will gain on economy because of the increased volumetric efficiency.

If, however, you can't pull top gear at usual (say 50-60 mph) speeds, or into a headwind then you're going to lose out when you change down.

In my experience, most bikes will pull a higher gear - I'd try 10% for starters.

 

[ELIMINATOR]

I should have said that this relates to my Yamaha FJ1200. Headwind won't be a problem.

 

[Timolgra]

If I were to change to a 19/38 from 17/40 then at 90mph the rpm drops to 4641, as opposed to the current 5460.

Will this reflect in the fuel consumption? Or isn't it quite that simple?

A bike like your will definitely get better fuel consumption with that gearing because it'll have the power to pull top gear.

Just in case you coincidently made the right choice, it's always better to have an odd/even ratio.....like you have

 

[The Other PaulG]

Just in case you coincidently made the right choice, it's always better to have an odd/even ratio.....like you have

Why's that?

Genuine question, I'm interested to know why that would make a difference.

Paul G

 

[Myke Rocks]

couple of points

Why's that?

Genuine question, I'm interested to know why that would make a difference.

Paul G

I would guess the odd/even ratio is to do with chain life. It means the same rollers are not impacting on the same spots on the sprockets as often.

Another thought, from my motocross days.

When you change sprocket ratios, you also significantly change the "gap" between the gears, soementimes to your advantage, sometimes to your disadvantage.

Myke