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Tech. Advice: Series 'B' / 'C' 500cc/1000cc Bikes
Gear Ratios. Which gears are fitted?
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<blockquote data-quote="timetraveller" data-source="post: 44772" data-attributes="member: 456"><p>Well spotted b'knighted. I had not gone back and looked at the first posting again. The use of a 48, as opposed to a 46, toothed rear sprocket will increase the revs by 48/46. This means that my figure of 2,875 rpm should be 3,000 rpm. Probably well within the measuring errors for this kind of task. I often notice that people worry about what wheel size is used but it is not the wheel size but the rolling circumference of the tyre that is used. For example the choice between a standard twin with a 20 x 3.00 front tyre and a touring spec. bike (D) with a 19 x 3.50 should be negligable, i.e. they are both nominally a 26" wheel. The problem arises with modern tyres which often do not have a circular cross section so one needs to know the radial thickness of the tyre, not its width. It is easy to check if a mark is made on the tyre and the bike wheeled forwards on a piece of flat road an exact number of turns and then the total distance measured. Divide the total distance moved by the number of wheel rotations and then divide by pi, 3.14 is near enough for this, and you have the rolling diameter of your wheel. Sorry if this seems condescending but there might be people out there not used to old bikes and old tricks.</p></blockquote><p></p>
[QUOTE="timetraveller, post: 44772, member: 456"] Well spotted b'knighted. I had not gone back and looked at the first posting again. The use of a 48, as opposed to a 46, toothed rear sprocket will increase the revs by 48/46. This means that my figure of 2,875 rpm should be 3,000 rpm. Probably well within the measuring errors for this kind of task. I often notice that people worry about what wheel size is used but it is not the wheel size but the rolling circumference of the tyre that is used. For example the choice between a standard twin with a 20 x 3.00 front tyre and a touring spec. bike (D) with a 19 x 3.50 should be negligable, i.e. they are both nominally a 26" wheel. The problem arises with modern tyres which often do not have a circular cross section so one needs to know the radial thickness of the tyre, not its width. It is easy to check if a mark is made on the tyre and the bike wheeled forwards on a piece of flat road an exact number of turns and then the total distance measured. Divide the total distance moved by the number of wheel rotations and then divide by pi, 3.14 is near enough for this, and you have the rolling diameter of your wheel. Sorry if this seems condescending but there might be people out there not used to old bikes and old tricks. [/QUOTE]
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Tech. Advice: Series 'B' / 'C' 500cc/1000cc Bikes
Gear Ratios. Which gears are fitted?
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