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Pete's calibrations using John Disley's solid tire

Each year when I check the London Marathon course I use the same bike, provided by John Disley. It has a Suretrak solid tire. Weather conditions have been generally similar each year.

All calibrations shown are in counts per kilometer, all using a JO or, in 2008, a JR counter with a gear ratio of 23.636363… counts per revolution.

2002 10970.12
2003 10970.96
2004 10969.15
2005 10974.09
2006 10973.62
2007 10975.97
2008 10975.81

This is posted for what interest it may have. I draw no universal conclusions.
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Were they all on the East Ferry Road cal course. I cant remember if it has been resurfaced. Could that have caused the jump in 2005 due to a rougher surface?

Are you wobbling more as the years go by? I am sure I am.

Has Disley ridden miles on his bike and worn the tyre tread?

Just some of the effects that could be the right magnitude to account for the changes

I use a bike with solid tires. After seeing your post, I went back and pulled all my cals form one course. I also tracked the temp., and recorded the date of the measurement.

What I found was that over time (the course of 9 months, putting about 1000 miles on the bike over that period), my counts increased. I surmise that it could be due to wear of the tire, decreasing the circumference. I also noted that with higher temps, my counts went up, likely due to slightly softer rubber, effectively shrinking the circumference. However, total variance went from 18396 clicks per mile in the beginning (new tire) to 18414 clicks in the fall.

The variance in any month was less than 3 clicks per mile.

I like solid, as I don't worry about air loss, or worse, a flat during a measurement.

My 2-cents.

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