Gearing q or two.....plz be gentle

[Vishnuatepork]

Hey All;

I am looking into some special gearing for my VX project, and I was wondering if you might have a minute to answer a few q's I have.

I am looking at doing some custom cut gears.  I am considering a .75 ratio for 5th gear.

My question is this.
Does the height of the ratio matter at all?

Let me explain my question a bit.  I used to race bicycles a bit and I know that with a 18 speed (2 x 9) that there was sometimes a few gears that over lapped when in the 8th through 12th gear (depending on which rear cassette (gears) were chosen).  Some times it was advantageous for me to be in the smaller front sprocket, rather than the larger one, even though the ratio was larger, it was easier to turn.

That being said, I have a few options for the .75 ratio, 28/21 or 24/18.  does it matter ? does the engine (I hate saying this, cuz I know it sounds stoopid) "feel" or "notice" the difference in the height of the ratio?  I have been cautioned about being over geared, and thats the reason I ask. 

Cheers
Alan

[Peter Jack]

It shouldn't make any difference. I think probably it felt better on the bicycle because the cadence suited you better.

Pete

[panic]

Generally, more teeth engaged is preferred (at least, in the range you mention) to reduce ratcheting and local tooth loading, but the effect is small.

[wobblywalrus]

Alan, all sorts of good info about gearing is in "The Racing Motorcycle: A Technical Guide for Constructors" by John Bradley ISBN 0 9512929 2 7.  One of the best things he shows are the relationships between speed, engine torque curve, and gearing.  Also, lots of info about gears.  The last time I was in Portland they had several copies for sale at www.powells.com.  A sample page is attached.  It shows how the author explains things step-by step.  This is a British publication and it is metric.  I'll bet, if you work through all of the equations and graphs with data for your bike, you will find the answers you need.

 

[Vishnuatepork]

Wobbly,

Thanks for that, I think I 'll get it. 

I have a speed equation chart that does show the rpm to mph.  Maybe this author can teach me everything

Cheers
Alan

[panic]

"Which ratio to use?" and "what tooth count is best to achieve a known ratio?" are two completely different subjects.

[Vishnuatepork]

"what tooth count is best to achieve a known ratio?"

thats this topic

[Stan Back]

Whatsa VX?

[Vishnuatepork]

Sorry, Suzuki VX800. Motorcycle, shaft driven vtwin circa 1990.