Folding Bikes - Wheel size circumfrence for 20" Dahon D7?
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07-24-08, 10:39 PM
I just got a cheapo $8.60 Schwinn computer from Amazon. I am amazed by all the cool functionality they have in this little thing! For the wheel size I used the suggested 1596 mm . I notice my distances seem around 2% higher than google maps. So I lowered it to 1560 . Anyone done any scientific study to confirm the correct size ? I assume when Shwinn suggests 1596 they are probably assuming it is a BMX bike with big tires, not road tires.
Do a roll-out measurement: mark the floor, roll out a whole front wheel revolution, mark again, measure distance between marks. Easier of you start with the valve down.
07-25-08, 12:40 AM
Yeah, I used the 'suggested' setting on my Downtube. Was out by a lot compared to GPS.
Ended up with 1519 when measured by Prof Jur's method. The skinny tires on my other bike needed another measurement.
07-28-08, 08:51 PM
Thanks, I did the rollout and the number came to 1520, which is almost exact now with the google maps distances! The tires are Kenda, which came withe the Dahon D7. I was so happy at first when I saw myself easily cruising at 25-30 mph! Now these numbers will all drop a few mph!
07-29-08, 01:12 AM
When I put the pooter on my Downtube, I mistakenly set it to KM/h. Imagine my delight at the speeds that bike made..
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