When the factory engineers develop a new bike, one of the most important
things they have to do is optimize the gearing. They use their own test moto track with their own test riders. They use average
riders and the track is an average, generic track so what do they end up with?
Average gearing. But when you think about it, it's all about mass marketing.
That's a good thing though. If they manufactured a myriad of choices, delivery time would slump and manufacturing costs would
be passed along to us. A large number of riders will be content with this set-up, but more aggressive racers want a custom
gearing configuration. Let's look at some factors to consider.
To Gear Down or to Gear Up; That is the Question
This is really a personal preference but part of it depends on the tracks you ride on. Does it have a lot of
long straight legs where you can get up a head of steam? Lots of tight coffee-cup turns at the base of steep jumps?
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Gearing
up: this is achieved by by either using a smaller rear sprocket or a larger countershaft. The net effect is to add more speed
while lowering the final drive ratio.
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Gearing
down: achieved by using a larger rear sprocket or a smaller front sprocket. Net effect? It raises the final drive ratio, while
lowering speed. Great for climbing.
But What is the Final Drive Ratio?
Alright, it's time to apply that schoolhouse math. To arrive at the final
drive ratio, divide the number of teeth you've got on your rear sprocket by the number you have on your countershaft.
But what does the number tell you? It's the number of times your countershaft
will turn during one complete rear wheel rotation. A smaller number tells you that you'll experience higher RPMs for a certain
speed and a higher number is the opposite. Now it all makes sense, right?
Riding at Altitude?
If you're planning to ride at a high altitude, not only should you get there a day or so early to acclimate
and avoid light-headedness, but your ride needs modification too. Higher altitudes mean less engine power, so gear down to
compensate.
Clutch Implications
An interesting side effect is that the lower your gearing, the less you'll have to use your clutch. Why? Because
your engine will be more responsive and run freer.
What About the Power band at Higher Gearing?
Basically, it's the opposite of what we just discussed – you'll put a bit more wear on your clutch; but
on the other hand, your engine will be easier to control.
And Lower Gearing Power band?
In a low gearing configuration you'll find yourself shifting much more
often to stay in the sweet spot. It's just the opposite of taller gearing.
Be Your Own Pit Crew
Be ready to fine-tune your gearing configuration on the fly without having to change the chain. Put together
a starter pack to haul along with you to the track. Include a spare rear sprocket that's two teeth larger than the current
one and a countershaft that's one tooth less. The tooth ratio of rear sprocket to countershaft is ½:3.
*NOTE: As a rule of thumb, one tooth change at a time
in gearing is the max.
Wear and Tear: Your Sprocket Should Match Your Chain
If your existing chain is worn and you use it with a new sprocket, you'll be throwing your sprocket money away
because the sloppy chain links will wreak havoc with the new teeth.
Of Rear Sprockets and Countershafts
The smaller your countershaft is, the faster your chain is going to wear. It's a friction thing. Say you decide to ride
with countershaft that's one tooth smaller. Your best bet is to use your standard counter coupled with a new chain with an
extra link and a rear sprocket that's three to four teeth larger. But avoid the temptation to lengthen the chain with an extra
master link; that's asking for trouble!
