# Efficient Use of Power on a Motorcycle: The Impact of Changing Sprocket Sizes

• Frankster
Frankster
How did you find PF?
Searching for an equation to determine if force and ratios are linear.
In this scenario, the only values that change are the sprocket sizes, weight and the number of teeth. My question relates to efficient use of available power. On a motorcycle, I have a front sprocket with 14 teeth and a rear sprocket of 48 teeth. The chain length is 120 links and it is a 520 gauge chain. The power at the drive shaft is 'constant' as is the size and weight of the rear wheel and the unsprung weight. We can assume that each sprocket has half of its teeth in contact with the chain at all given times.

What I am keen to determine is the effect of changing the sprocket sizes while still keeping the same ratio. As an example, if I use a 28 tooth front sprocket and a 96 tooth rear sprocket or a 7 tooth front sprocket with a 24 tooth rear sprocket. What will the effect be on acceleration, force exerted on the drive shaft and wear on the chain and sprockets. Obviously, the weight of the sprockets will change as they get bigger or smaller and the number of teeth in contact with the chain will also change as will the length of the chain needed to maintain the same distance from the drive shaft to the rear axle.

Assume the weight of the sprockets changes with the number of teeth e.g. 7T sprocket is half the weight of 14T and 28T will be doubled the weight of 14T sprocket. Chain weight will increase slightly when used with larger sprockets and decrease with smaller sprockets. My brain tells me there will be no effect on acceleration regardless of size of the sprockets, but I am curious to hear what the forum members think.

Last edited by a moderator:
Welcome to PF.

This is the introduction sub-forum. No questions allowed here. Post your question in the appropriate subforum. Also, I suggest you read the rules. This is a very friendly forum, but there ARE a few rules and they are followed.

phinds said:
Welcome to PF.

This is the introduction sub-forum. No questions allowed here. Post your question in the appropriate subforum. Also, I suggest you read the rules. This is a very friendly forum, but there ARE a few rules and they are followed.
Thanks. You can delete that introduction.

Welcome to PF; there's no need to delete your introduction. I think it's a very good question. Please repost in the Mechanical Engineering forum and you will get great responses. I'll go ahead and lock this intro thread.

Frankster

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