General Discussion Triathlon Talk » How many MM is the circumference of my 700x23 tires? Rss Feed  
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2011-09-14 3:38 PM

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Subject: How many MM is the circumference of my 700x23 tires?

My darn bike computer reset itself the night before Rev3 Full last weekend and I'd like to restore its sanity... it took 15 miles or so to realize I wasn't really going 15mph...



2011-09-14 3:41 PM
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Subject: RE: How many MM is the circumference of my 700x23 tires?
2011-09-14 4:26 PM
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Subject: RE: How many MM is the circumference of my 700x23 tires?
You could measure if you wanted to be sure...
2011-09-14 5:37 PM
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Subject: RE: How many MM is the circumference of my 700x23 tires?
Thank you much!
2011-09-14 6:41 PM
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Subject: RE: How many MM is the circumference of my 700x23 tires?

FuryUs - 2011-09-14 6:26 PM You could measure if you wanted to be sure...

You should absolutely measure!  I used one of the standard measurements for a while and then I noticed once that my computer and mapmyride.com differed by a full km over 60k.  So I measured the tire and when I used the new number, it matched up with mapmyride much better.

2011-09-14 6:43 PM
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Master
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Subject: RE: How many MM is the circumference of my 700x23 tires?
Yes, measure it at your normal psi and your weight on it. Mark a spot on the ground where the valve stem is, roll one revolution and measure the length


2011-09-14 6:51 PM
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Subject: RE: How many MM is the circumference of my 700x23 tires?

Av8rTx - 2011-09-14 6:43 PM Yes, measure it at your normal psi and your weight on it. Mark a spot on the ground where the valve stem is, roll one revolution and measure the length

 

Will def do this.

2011-09-14 7:05 PM
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Subject: RE: How many MM is the circumference of my 700x23 tires?
I just did this Sunday to double check after I replaced the batteries.  2106 without weight, 2095 as I ride.
2011-09-14 7:31 PM
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Subject: RE: How many MM is the circumference of my 700x23 tires?
I'm going to go make some popcorn. I seem to recall a giant discussion about if it makes a difference in the actual rollout distance with the riders weight on the tire.
2011-09-14 7:35 PM
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Subject: RE: How many MM is the circumference of my 700x23 tires?

Turnin2 - 2011-09-14 7:31 PM I'm going to go make some popcorn. I seem to recall a giant discussion about if it makes a difference in the actual rollout distance with the riders weight on the tire.

I doubt difference quoted by the previous poster makes much of a difference in actual mileage, this is what I have read in the past to get an accurate measure. FWIW I have probably done this once, years ago and probably 6 or 7 bicycles ago. I just use the chart the computer comes with and ride now. I do know my Cateye wireless tends to be a tad generous on the miles but I don't believe it is seriously compromising my training or anything.

2011-09-14 8:10 PM
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Subject: RE: How many MM is the circumference of my 700x23 tires?

Being off a few millimeters makes very little difference -- about one part in a thousand per mile.  So if you're high or low by, say, 3 millimeters, then for every 1000 miles you thought you rode, you actually rode 999 ('roughly').

I'll venture to say that this difference makes no difference at all in training or in racing.

 


The fine print:

Suppose OP reports 2096 (the default on my computer) as the diameter.  Then the computer says that every revolution is 0.001302394 of a mile (assuming it even works to that precision), which means it takes (according to the computer) 767.81680505284883 revolutions to make a mile.  Suppose the actual diameter is 2093.  Then the computer says that every revolution is 0.0013005299 of a mile, for 768.91734669076044 revolutions per mile.  The difference is pretty darned close to 1.1 revolutions, or a little more than a thousandth of a mile.



2011-09-14 8:45 PM
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Subject: RE: How many MM is the circumference of my 700x23 tires?
However if you accidentally get your computer in Km/hr instead of mph then that 30 you're riding is really about 18.6 mph.  I thought my training was finally starting to pay off!
2011-09-14 11:23 PM
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Subject: RE: How many MM is the circumference of my 700x23 tires?

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