Gearing... Front Vs. Rear Sprocket Changes

Just curious if anyone has noticable differences between front and rear sprocket changes. I understand gearing… I usually just change the rear sprockets. This passed weekend I learned some of my competitors were running a smaller front sprocket to me and they were flying. I run a 20T front on the 206.

I take it you are asking if there is a difference between:

There are endless argument elsewhere on this.
The only think I can see is less weight / more ground clearance with the smaller gear.

ETA: the exact argument is a bigger 20T driver gives more top end vs bottom end or vice versa relative to a smaller 15T driver of the same ratio. Then there a friction component to the argument. No one can prove anything, blah, blah, blah then there is name calling and it gets personal. My take is prove it. Barring that it is opinion vs opinion and theory vs theory.

My 2nd take is there are bigger problems to solve.

FWIW there are a few other debates on LO206 I never see conclusive answers to.

It is my belief in theory smaller gears weight should off set the friction and ratio being equal the smaller diameter less rotating weight wins. I can’t prove it though.

Is that the topic?

This too is a guess mike - but I’d have thought the most influential variable is likely to be losses through the chain, bending through the more acute angles on small sprockets.


This debate is as old as karting itself.

I’m still of the opinion that any effects you see from changes in front driver (rolling resistance changes) are so small they are negligible.

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Old argument indeed!
On the plus side for Smaller over all sprockets:

  1. Lighter weight.
  2. Lighter rotating weight.
  3. Usually has a shorter chain by a couple of links.

On the negative side for Smaller over all sprockets:

  1. Chain bends through a tighter angle - more friction.
  2. Chain wears more quickly - worn chains have more drag.
  3. Sprocket wears more quickly - worn sprockets have more drag.

On the plus side for Larger over all sprockets:

  1. Chain has to bend through a shallower angle - less friction.
  2. Chain wears more slowly.
  3. Sprockets wear more slowly.

On the negative side for Larger over all sprockets:

  1. Chain is usually longer - more weight.
  2. Sprockets are heavier - more weight.
  3. Larger diameter sprockets run closer to the ground and are more susceptible to dirt and the resultant wear.
  4. Larger diameter sprockets make the chain run closer to the ground and are more susceptible to damage and wear.

Another difference between small and large sprockets happens when you need to change ratios slightly. Adding or removing a tooth from the rear sprocket ends up being a smaller “step” with the larger sprockets. It give a finer resolution to your gearing changes, a potential advantage.

all the math exists to evaluate this. it comes out to being relatively negligible on all fronts.

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I have witnessed all aspect of ‘The Argument’. It usually goes with guys alluding to a fact, but won’t commit to stating a fact, so I don’t know what way they are going.
I don’t know if the chain angle would be as much as the weight in the end result. Seems lube would mitigate that. This is one of those areas where guys are not clear and make statements like it is self evident but I can’t see what side of the argument they take. I have never seen quantification of the friction or any of factor or the theory involved. I don’t know the difference in angle by changing teeth count either. So most take a stance but can’t explain reasoning. Some I think are just trolling the topic.

You have to ask yourself why your competitors where making large changes in gearing. Two scenarios might be they were running different size rear tires, or the atmospheric pressure was much lower than normal.

Any chance that those other guys switched from #35 to #219 chain?

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With a 3.0 gear ratio (I can’t guess what you’re running) this would be her options if you wanted to change both sprockets. You can see there’s about 3 teeth difference on the axle when you change one on the engine. Tell me your gear ratio and I’ll make a chart for that. This is an Excel spreadsheet, if you want a copy of my collection email [email protected] and request your copy of “nine sheets”.