Consequences of changing pinion z11 to z10!?

Hello guys.

Imagine that I’m running my kart with z11 pinion and 77 sprocket. If I changing the pinion to z10, what is the rest of the things that should do?


By “Pinion z11 to z10” I assume you mean the drive sprocket on the clutch/engine.

Change the rear sprocket range to maintain similar gear ratio. Otherwise you find yourself hitting the limiter far shorter than before. Upside is that your rear sprocket will also be smaller and less likely to pop a chain if you drop a wheel off track.

If you are running a Rok or Rotax, you will have to grease the bushing occasionally compared to the needle bearing on the 11t sprocket.

What engine are you running? Put simply, going from an 11 to a 10 will result in better acceleration but a lower top speed. But it does depend on the engine and track.

This chart can help you visualize these changes:

that is a 7.00 ratio

so, 10-77 = 7.70 ratio

That’s a big change. Its like adding this many teeth to 11-77 rear sprocket to make it as close to 10-77:
that’s 8 teeth so, 11-85.

Big change. The front sprocket is one you don’t generally use for incremental changes. The bigger, back sprocket is more common.

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Thks guys!

I’m running a iame x30.

I’m thinking use this changing when i have a rainy race. And in this case, I need more acceleration and a lower speed!

That’s correct?

What is the cases that you guys do the same modifications (z11 to z10)?


I think for a rain race, you want the opposite. More speed and less acceleration. When you are down on grip and you go with more torque out of the corners you are more likely to break traction on the rears and slide losiing momentum. You typically will go down in gear ratio (bigger front sprocket or smaller rear sprocket). The front sprocket is a big change compared to the rear, unless you drop teeth on the rear respectively.

No, you usually go up in ratio for rain because of the lower corner speeds. Pretty common to just swap to the smaller front driver for rain.

Your right foot is the traction control.


Yeah a front driver change can be a good way to go depending on the track and how wet it is. You’ll want to move in the direction of acceleration (Drop a tooth on the drive sprocket) vs top speed or you’re going to get absolutely smoked.

Make adjustments to throttle mechanism if needed, you can even use brake to control power. Generally not needed though.

I hear what you are saying. Its been so long since I have raced in the rain, maybe my memory is failing me. It doesn’t rain a whole lot in North Texas and when it does, there is usually a tornado in the area.

The X30 is probably easier to modulate the throttle on than my RoK GP. Even in the dry you have to gradually give it throttle or it won’t spool up as quick. I haven’t raced it in the rain yet, but with that mid-range torque I feel like its going to be a handful.

It might be a handful, but if you gear it to be more manageable you’re going to out of the useful powerband once you’re out of the turn and you have more traction again on the straight, especially out of the tighter turns.

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Thks guys. Great inputs from you all!

So, I’m not clearly about when you choose reduce the pinion instead grow up the rear sprocket. Which cases you choose reduce the pinion to lower tooth?


Always gear for your power band. If it is wet, your speed everywhere will be lower, so dropping a tooth on the front will raise the rpm back to where they are in the dry (if you are going 16/17ths the speed in the wet). A bigger gear up front in the wet will mean you are going to be way below the powerband, assuming the gearing in the dry is a good baseline to compare to.


As Caleb said, you gear to your powerband. In the dry you want a certain gear ratio based on your average speed and RPM but in the wet your speed and RPM will be lower as you have less corner speed, so you’ll want to have a larger he’s ratio to compensate.

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Ok another questions.

Imagine that im using rear 77 sprocket and z11 pinion. Suddenly I will have a heat with raining weather. I start with changing the pinion to z10 and in your opinion I should keep the 77 sprocket or adjust too?

In theory of course, imagine that I don’t have time to practice with the same conditions (raining).

What you would do? :wink:

Sory for that kind on questions, but I have a very few hours driving at the rain.