How to Pick the Right Gearing

Every week I get some e-mails from our website about gearing and sprocket choices, and at least that many sprocket questions from customer phone calls, and the same questions are quite common in the paddock at any race. Sometimes the questions seem pretty simple, like "Hey, Paul, what gearing do I use on my SuperSport 600 for Daytona?" Sometimes the questions are a little more complicated, like "Hey, Paul, I'm having a really hard time getting a good drive out of turn 7 in the wet with my 170 HP superbike on slicks -what gearing should I use?". And I wish there was some easy, all-inclusive answer I could give to everyone that would help them out, but the truth is, gearing selection can be very critical and can cost you a race win if you make the wrong selection. Since there is no easy, all-inclusive answer, and it would take too many pages to cover every possible scenario, I am going to explain some basics about gearing choices and this should help you understand how to pick the right gearing for your bike, at any track, anytime.


Let's say you go to a track in a different region that you have never raced before, so you walk through the pits looking for someone you know with a bike like yours so you can ask what sprockets to run. He tells you the hot set-up, you go back to your pit and put 'em on, thinking "cool - now my first practice won't be a waste". Your practice session finally comes, you head out and promptly bounce off the rev limiter at the end of the long front straight. What gives? The guy you asked usually knows what he is talking about.... usually.

The answer is:
Everyone has different riding styles with weaknesses and strengths around
any given track, and not all bikes are created equal.


Did you get that? Too simple you say? Maybe not as simple as you might think. We'll break it down and look at the first part of that answer, different riding styles. For our first example, we'll use a smooth third gear right-hander leading to a long 6th gear straight. Three different racers with three different riding styles, all racing identically prepared Yamakasuki 600's, all with the same gearing, a 15 tooth front and a 45 tooth rear, for a 3.00 ratio. (45 divided by 15 = 3.00) See sprocket chart at bottome.


Racer #1 brakes late, maximizes the available track surface, and gets
on the gas before the apex (works best for most turns).

Racer #2 gets his braking done early, then turns it in tight (OK when protecting
the inside line, but not the best way through).

Racer #3 is late on the brakes, trails the brakes past the apex and then gets
on the gas (usually not right either).


Looking at Racer #1 we see he has an experienced riding style. He arcs in nice and wide, brakes late, rolls on the gas as he approaches the apex, gets a good early drive and pulls top gear right to peak horsepower down the next long straight before he gets off the gas for the next turn. His gearing is just about perfect for this bike and his riding style, at least for this section of our make-believe track. Racer #1 is the guy we hate to have in front of us on the track because he is that sombitch that is so damn hard to pass.

Racer #2 gets off the gas early and on the brakes early, thus allowing him to roll into the turn early. Although he thinks this is the fast way through the turn, it really means he goes in too tight, which throws off his apex and he gets a late drive coming onto the next straight. At the end of the straight he has barely clicked top gear, and it's time to brake too early once again. He may actually have pretty good corner speed, but his 'in tight - out wide' riding style screws up his exit and makes him flate getting in the gas and translates into low terminal speed on the straights. This cornering style is typical of beginning racers, it is easy to spot on the track, and even easier to pass. Racer #2 might drop his lap times significantly by increasing his sprocket ratio (higher ratio number) to gain better acceleration off the turns at the expense of top speed, which he is not seeing anyway. He should try adding 2 or 3 teeth to the rear (or possibly 1 off the front) and then work on his riding style, hopefully dropping those teeth off again as he improves his riding skills.


Racer #3 comes into the same turn, brakes late, but his turn-in point is not as far to the outside of the turn entry area as it should be, and so his arc into the turn is off a bit and he trails brake all the way past the apex. This means he will then get on the gas late, and doesn't get as good a drive as he could. Many racers have styles like Racer #3 - just spend a few minutes at any local race watching a medium fast turn like the one in our example. While you watch a few guys come through, listen to their exhaust noise. You will see and hear them get off the throttle, trail brake into the turn, and after the apex is passed you hear the the guy roll into the throttle. This is a racer that has progressed a bit from the early learning stages, and is braking later, but hasn't yet mastered the art of maximum corner speed and early application of the acceleration control device in his right hand. The fastest way through a corner with the best drive down the straight almost always involves being on the gas sooner, rather than later. Like Racer #2, Racer #3 won't pull to the HP peak down the next long straight either. Adding one or two teeth to the rear may help improve his times by adding a little more acceleration off the turn but not capping top speed too much. This racer needs to practice getting on the gas at, and then before the apex in the turns. When he can do that consistently, he will need to pull taller gearing down our make-believe straight and he will have to drop those one or two teeth off the rear sprocket allowing him to improve his laptimes.

Now let's make up another racer coming into our same make-believe corner. An expert level racer with a few years experience. This guy brakes late, has good corner speed, gets on the gas early, but can't stay with his buddies on similar bikes down the straight. What's up with that? Probably he is geared too low (numerically higher ratio number - this can be confusing!), perhaps a 15/47 instead of the 15/45 we used in our senario above, and he is over-riding his gearing, constantly reving past the HP peak in the RPM range. This is mistake that many racers make, beginner through pro - they select their gearing to pull maximum RPM, not the RPM of maximum horsepower. This is such an important concept it bears repeating: gear your bike for the RPM of maximum horsepower, not maximum RPM. Get a dyno chart for your bike, know where your peak HP is (usually not maxRPM), and don't try to rev way past it. You will go faster by shifting just past the HP peak, where the RPM will then drop to just before the peak, and you pull through the meat of the powerband again, rather than shifting way past the peak and then accelerating through a declining HP curve to reach max RPM on your tach. At the end of the longest straight on the track you should ideally be at peak HP, not peak RPM. I'm about to drift into another subject area here, so let's get back to gearing, and maybe we'll talk more about HP curves in a future article.

The second part of our answer was: not all bikes are created equal. Some bikes just run better than their siblings straight from the factory. Manufacturing tolerances are a real thing, and if eveything is just right or just wrong from the assembly line, you will see the difference on the dyno and on the track. And I am going to tell you now that if your bike is one of the "just wrong" ones you have an uphill battle trying to run with the "just right" bikes unless you go though the motor and make it just right or close to just right. I know what you are thinking- "boy, that's gonna cost me a left nut!", but keep your credit card in your wallet for now. While you are saving up the money to do the motor, you can help overcome a shortfall of HP by following the gearing principles we have talked about in this article. Know your riding strengths and weaknesses, get a dyno chart, and think about what sprocket choice will help you overcome your and your bikes' weaknesses without hurting the strengths. How about the tires on your bike? They also help define how two similar bikes may not be equal on the track. Of course an raggedy old take-off with 35 heat cycles on it won't help anybody do anything but go slow and fall down, however keep in mind your rear tire is the last part of your gearing equation, and the rolling circumference can be a bigger or smaller number just like the number of sprocket teeth. We'll do one last example to illustrate this point:

Joe Racer and Ricky Racer have identical bikes with identical gearing, but Joe runs Brickstones and Ricky runs Dunslops. A quick check with a tape measure reveals the Brickstone actually has a two inch larger rolling circumference compared to the Dunslop. This means that for each rotation of the rear wheel Joes' bike will move forward two inches more than Rickys' bike. Seems insignificant, but an average 180/55x17 race tire mounted on a 5.5" rim has a circumference of about 80 inches and rotates 33 times a second at 150mph! Adding just two inches extra circumference changes the overall gearing (and engine RPM) by about 2.50% and at 14,000 RPM that two inches means your tach now reads 13650 RPM, not 14000 RPM. If we are using a 15/45 sprocket set with a 3.00 ratio, a quick check of the math reveals that a +2.50% change would reduce the overall gearing by .075%, effectively decreasing our 3.00 ratio to a 2.925. (Note to engineers and mathematicians: I know the actual sprocket ratio is still the same, but the overall ratio has nonetheless changed because of the different tire circumference) This would require a gearing change to compensate and make the two bikes perform similarly on the track. Time to break out the sprocket chart again. If you don't have one in your toolbox, go to sprocket ration chart at bottom and click your printer icon. You need a sprocket chart at the track. Anyway, if you look at the chart you will see that to increase a 2.925 ratio to approximately a 3.00 ratio you will need to add a tooth to the rear sprocket. What about going from DOT's to slicks? Same situation, and any experienced racer who has run DOT's and slicks on the same bike at the same track can tell you there is a noticeable difference in RPM and shift points around the track, because like different brands of tires, slicks and DOT's (even from the same manufacturer) almost never have the same circumference. Some people run a 190 on a 5.5" rim, most people use a 180 on a 5.5", some use a 170. Rest assured this also changes overall gearing. The point is, just because you run the same sprockets as someone else does not mean you are necessarily running the same overall ratio.

Well, that just about covers the basics of how to choose correct gearing. Some of you reading this will say "Wow, this might really help my racing this year!" It will. Some of you reading this will say "all this gearing and sprocket ratio stuff is fine for the serious racer, but I do OK at the tracks in my region with the same stock sprockets that came on my bike". Nothing wrong with just doing OK. But isn't the point of racing to try and win or at least improve? Considering the overall expense of racing, a few extra sprockets in your spares box won't kill your budget, and if you take the time to figure out the best combination for you and your bike at each track you race, they might just put you on the box more often. And hey, maybe I will get fewer emails to answer about gearing....

Paul Wright

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