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Discussion Starter · #1 ·
When i get the CBR300R, I'd like to use bicycle velocity meter to measure speed correctly. For this I must enter tyre's circumference in millimetre. If any can give me these values, I'd much appreciate your kindness.
 

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With the variables of mass production and pressure affecting the tire circumference, for accuracy you'll really want to take the measurement from your own bike and not from someone else's.

Also, on these bikes the speedometer is getting it's signal from a sensor in the gearbox, so the size of the front tire is immaterial as far as the speedometer readout is concerned. It's the size of the rear tire that affects the speedo readout.
 

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With the variables of mass production and pressure affecting the tire circumference, for accuracy you'll really want to take the measurement from your own bike and not from someone else's.

Also, on these bikes the speedometer is getting it's signal from a sensor in the gearbox, so the size of the front tire is immaterial as far as the speedometer readout is concerned. It's the size of the rear tire that affects the speedo readout.
He wants to use a bicycle speedometer which uses a magnet attached to the front rim and sensor to count the wheel rotations to compute speed. Probably because of 10% speedometer error in other countries.

With IRC road "wieners" the circumference is 575 mm. Oops, that is the diameter. Bicycle speedo's that I have used want the tire diameter. Let me find my slide rule and get back to you.

circumference = 1,805.5 mm
 

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Here's an alternative way of working it out. You will need a flat smooth surface like a concrete floor in a garage.

Tape two pieces of white A4 paper to the floor at centers roughly equal to the circumference. We know its going to be around 1.8m from the calculation made by old crony.

Roll the bike over the first piece of paper and just before the front wheel moves over the middle of the paper scribe a line about half an inch wide across the crown of the tyre using a black ink pen. Do it as low as possible.

Now continue to roll the bike over the first piece of paper and aim in a straight line for the second piece.

Just before the mark on the front tyre disappears underneath for the second time re-mark it exactly over the top of the old mark so the ink is freshened. (its easier if someone can do this for you)

Continue to roll the front wheel over the second piece of paper and out of the way.

Measure the distance between the two pen marks on the pieces of paper. This is your bike tyres circumference.
 

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Discussion Starter · #5 ·
He wants to use a bicycle speedometer which uses a magnet attached to the front rim and sensor to count the wheel rotations to compute speed. Probably because of 10% speedometer error in other countries.

With IRC road "wieners" the circumference is 575 mm. Oops, that is the diameter. Bicycle speedo's that I have used want the tire diameter. Let me find my slide rule and get back to you.

circumference = 1,805.5 mm
Thanks a lot:angel:. BTW is the figure for the front, or the rear tyre? I assume road "wieners" = front tyre.
 

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Discussion Starter · #6 · (Edited)
Thanks kiwi rider. I'm kind of lazy and not mechanically inclined. I only need to know rough figures of actual speeds as opposed to CBR300R's speedo display at 80, 90, and 100 km./hr. That way I can ride fast, but within speed limit, and also to to ride(cruise?) according to plan when I take a long highway trip.
 
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