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Gearing ratio question


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You DRZ guys know your stuff here so I thought I would ask you guys this question. I sold my beloved DRZ and YZ and I bought a 09 450 EXC. Love it! The bike came with 15 front 45 rear sprockets. Stupid gearing. After much research It seems most people seem to run 14 front, 50 rear for a 3.57 ratio. That requires throwing away brand new sprockets and the chain and buyinmg new$$$$. I see that 13 front and stock 45 rear would get me close, at 3.46.

My questions is and probably a dumb question, If the ratio was the same would there a difference in torque at the wheel using a different combo of getting to that ratio final ratio?

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Your rear wheel would have a smaller moment of inertia given a smaller rear sprocket. Not sure if it's significant in the world of dirt bikes, but in theory that would allow more efficient use of your torque (faster acceleration/deceleration, less load on the brakes, etc.). You could determine the significance if you knew the weight difference of the 45- and 50-tooth sprockets, as well as the sprocket diameters or something about their mass distribution.

Haha that, or I have no idea what I'm talking about.

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Gear ratio is gear ratio. Makes no difference to torque how you get it. BUT for chain life, it is desirable to run as large a countershaft sprocket as reasonable. For you that is 14.

As an alternative, run the 13/45 until you need replacements then go to 14/50

Where and how do you ride? For many people 13/50 or even 13/51 is a choice for tight stuff.

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I ride in all terrain. I live in Anacortes so we have some trails you can putt around here. Putting because of hikers and whatnot. So I ride around town and Ill ride single track at walker valley, you know steep, slippery roots and rocks after I get my first scratch or 2 on my new bike. Also out in the desert outside of Bend OR for high speed stuff. I want to get it set up eventually after a wear this set out to get a setup where I can switch the front sprocket out for woods and swap it out again for street/desert.

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Your rear wheel would have a smaller moment of inertia given a smaller rear sprocket. Not sure if it's significant in the world of dirt bikes, but in theory that would allow more efficient use of your torque (faster acceleration/deceleration, less load on the brakes, etc.). You could determine the significance if you knew the weight difference of the 45- and 50-tooth sprockets, as well as the sprocket diameters or something about their mass distribution.

Haha that, or I have no idea what I'm talking about.

HA ha thats good. The scary thing is I was following you. Humm not sure I am worried about the weight to inertia at this point. But sounds like if I leave the smaller back one on Ill have the advantage over those big $100+ orange and black spockets these guys have. ­čśĆ)

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