I recently acquired a new cycle computer. Leads broke on the old one. There was a table in the manual relating tire size and calibration setting, which I understand to be the distance the wheel travels in mm in one revolution. The table for the new one had 2146 mm for 700x25 which is what I have. The setting for the old one was 2124 for that size. I decided to measure it. I set up a piece of masking tape on the ground along a wall in my garage for a track to follow, and made a mark with a felt pen on the side of the tire. Then I got on the bike and lined it up with the tape and had my s.o. make a mark on the tape when the tire mark was bottom center and then rolled myself along the wall staying next to the tape, until the tire mark was down again and another mark was made on the tape. I figured I needed to be on the bike to account for the flattening of tire due to my weight (tire was at my usual ridding pressure, 100 psi, I weigh about 180). Anyway I got 2089 mm. This is 2-3% less than those table numbers. Is this a plausible result? Has anyone else done this and got a similar result? Any problem with my technique as described?
This is 2-3% less than those table numbers. Is this a plausible result? Has anyone else done this and got a similar result? Any problem with my technique as described?
Tire widths can vary up to 10% from their nominal size. The difference is usually not very significant.
It is better if you measure over two or three revolutions of the wheel as that will minimize the errors in marking the index points on the ground. You should also repeat the process enough times that you get repeatable results within a small margin of error.
I recently acquired a new cycle computer. Leads broke on the old one. There was a table in the manual relating tire size and calibration setting, which I understand to be the distance the wheel travels in mm in one revolution. The table for the new one had 2146 mm for 700x25 which is what I have. The setting for the old one was 2124 for that size. I decided to measure it. I set up a piece of masking tape on the ground along a wall in my garage for a track to follow, and made a mark with a felt pen on the side of the tire. Then I got on the bike and lined it up with the tape and had my s.o. make a mark on the tape when the tire mark was bottom center and then rolled myself along the wall staying next to the tape, until the tire mark was down again and another mark was made on the tape. I figured I needed to be on the bike to account for the flattening of tire due to my weight (tire was at my usual ridding pressure, 100 psi, I weigh about 180). Anyway I got 2089 mm. This is 2-3% less than those table numbers. Is this a plausible result? Has anyone else done this and got a similar result? Any problem with my technique as described?
Good methodology and, yes, that's a reasonable number.
-- Andrew Muzi www.yellowjersey.org Open every day since 1 April, 1971
I recently acquired a new cycle computer. Leads broke on the old one. There was a table in the manual relating tire size and calibration setting, which I understand to be the distance the wheel travels in mm in one revolution. The table for the new one had 2146 mm for 700x25 which is what I have. The setting for the old one was 2124 for that size. I decided to measure it. I set up a piece of masking tape on the ground along a wall in my garage for a track to follow, and made a mark with a felt pen on the side of the tire. Then I got on the bike and lined it up with the tape and had my s.o. make a mark on the tape when the tire mark was bottom center and then rolled myself along the wall staying next to the tape, until the tire mark was down again and another mark was made on the tape. I figured I needed to be on the bike to account for the flattening of tire due to my weight (tire was at my usual ridding pressure, 100 psi, I weigh about 180). Anyway I got 2089 mm. This is 2-3% less than those table numbers. Is this a plausible result? Has anyone else done this and got a similar result? Any problem with my technique as described?
Mike
I think 2089 mm is a little on the low side, but within 1%. I measured my Michelin Pro Race 25 mm tire and the number 2115 mm came up. Your method is OK. Do some more runs and average the results. I prefer some touch up paint on the tire. The paint leave marks on the floor. I find this more convenient.
I recently acquired a new cycle computer. Leads broke on the old one. There was a table in the manual relating tire size and calibration setting, which I understand to be the distance the wheel travels in mm in one revolution. The table for the new one had 2146 mm for 700x25 which is what I have. The setting for the old one was 2124 for that size. I decided to measure it. I set up a piece of masking tape on the ground along a wall in my garage for a track to follow, and made a mark with a felt pen on the side of the tire. Then I got on the bike and lined it up with the tape and had my s.o. make a mark on the tape when the tire mark was bottom center and then rolled myself along the wall staying next to the tape, until the tire mark was down again and another mark was made on the tape. I figured I needed to be on the bike to account for the flattening of tire due to my weight (tire was at my usual ridding pressure, 100 psi, I weigh about 180). Anyway I got 2089 mm. This is 2-3% less than those table numbers. Is this a plausible result? Has anyone else done this and got a similar result? Any problem with my technique as described?
Plausible. Technique as described is faultless. What is the tire pressure and your weight? Tire pressure difference can generate a 20 mm difference. If you are 150 lb and running 120 psi, I would recommend you redo the measurement and rethink all the details or your procedure. Measure again anyway and see if your number is reproducible.
I recently acquired a new cycle computer. Leads broke on the old one. There was a table in the manual relating tire size and calibration setting, which I understand to be the distance the wheel travels in mm in one revolution. The table for the new one had 2146 mm for 700x25 which is what I have. The setting for the old one was 2124 for that size. I decided to measure it. I set up a piece of masking tape on the ground along a wall in my garage for a track to follow, and made a mark with a felt pen on the side of the tire. Then I got on the bike and lined it up with the tape and had my s.o. make a mark on the tape when the tire mark was bottom center and then rolled myself along the wall staying next to the tape, until the tire mark was down again and another mark was made on the tape. I figured I needed to be on the bike to account for the flattening of tire due to my weight (tire was at my usual ridding pressure, 100 psi, I weigh about 180). Anyway I got 2089 mm. This is 2-3% less than those table numbers. Is this a plausible result? Has anyone else done this and got a similar result? Any problem with my technique as described?
One way to improve the method is to put masking tape on the wheel, a piece of tape on the ground, match the edges of the masking tape exactly, roll out, then have your laboratory assistant put a piece of tape on the ground to match the registration edge of the tape on the wheel.
On Tue, 30 Jan 2007 21:27:25 GMT, Michael Press <[email hidden]>
Quoted message said:
In article <[email hidden]> ,
Mike McGuire said:
I recently acquired a new cycle computer. Leads broke on the old one. There was a table in the manual relating tire size and calibration setting, which I understand to be the distance the wheel travels in mm in one revolution. The table for the new one had 2146 mm for 700x25 which is what I have. The setting for the old one was 2124 for that size. I decided to measure it. I set up a piece of masking tape on the ground along a wall in my garage for a track to follow, and made a mark with a felt pen on the side of the tire. Then I got on the bike and lined it up with the tape and had my s.o. make a mark on the tape when the tire mark was bottom center and then rolled myself along the wall staying next to the tape, until the tire mark was down again and another mark was made on the tape. I figured I needed to be on the bike to account for the flattening of tire due to my weight (tire was at my usual ridding pressure, 100 psi, I weigh about 180). Anyway I got 2089 mm. This is 2-3% less than those table numbers. Is this a plausible result? Has anyone else done this and got a similar result? Any problem with my technique as described?
This works even better if you do it for more than one revolution.. For instance measure out and do it for ten revs.. I have a measured 100 feet on the road in front of my house and by counting the revs to the nearest turn, I can reduce the possible error even further..
There was a table in the manual relating tire size and calibration setting, which I understand to be the distance the wheel travels in mm in one revolution. The table for the new one had 2146 mm for 700x25
Here's what I did: I put tape (non-stretching type) around the wheel and cut it off at the exact length. Then take the tape off, put it on the ground (some flat surface) and measure its length. It was interesting to see how different the results were for different wheels/tires.
On Tue, 30 Jan 2007 21:27:25 GMT, Michael Press <[email hidden]>
Quoted message said:
In article <[email hidden]> ,
Mike McGuire said:
I recently acquired a new cycle computer. Leads broke on the old one. There was a table in the manual relating tire size and calibration setting, which I understand to be the distance the wheel travels in mm in one revolution. The table for the new one had 2146 mm for 700x25 which is what I have. The setting for the old one was 2124 for that size. I decided to measure it. I set up a piece of masking tape on the ground along a wall in my garage for a track to follow, and made a mark with a felt pen on the side of the tire. Then I got on the bike and lined it up with the tape and had my s.o. make a mark on the tape when the tire mark was bottom center and then rolled myself along the wall staying next to the tape, until the tire mark was down again and another mark was made on the tape. I figured I needed to be on the bike to account for the flattening of tire due to my weight (tire was at my usual ridding pressure, 100 psi, I weigh about 180). Anyway I got 2089 mm. This is 2-3% less than those table numbers. Is this a plausible result? Has anyone else done this and got a similar result? Any problem with my technique as described?
This works even better if you do it for more than one revolution.. For instance measure out and do it for ten revs.. I have a measured 100 feet on the road in front of my house and by counting the revs to the nearest turn, I can reduce the possible error even further..
Bob
Find mile markers and use them. I have a stretch of about 8 miles w/ markers every mile. If the computer says you've done more than a mile when you hit the marker increase circumference. You can get it so you can pick a tire model/size, consider the pressure (I vary according to type of ride, and whether I'm sore) and the tire wear and know exactly how to set the computer. My computer measures by 1/100'th, and in 8 miles I can set it so I'm within about 2/100'ths mile, which is what, about 2/800'th (=.0025) or about .25% accuracy
On Tue, 30 Jan 2007 16:55:07 -0500, Bob Flumere <[email hidden]>
Quoted message said:
This works even better if you do it for more than one revolution.. For instance measure out and do it for ten revs.. I have a measured 100 feet on the road in front of my house and by counting the revs to the nearest turn, I can reduce the possible error even further..
Over the years by comparing with other riders and, recently using a Garmin 201, I know a certain spot from my home is 11.88 miles. I set a new cyclometer to an estimated value and correct to the known spot. For my usual, 700x23 Michelin Carbon tires, 2092 mm works. When only 3 digits are available, 209 works fine too.
Find mile markers and use them. I have a stretch of about 8 miles w/ markers every mile.
I've found road markers on CA state roads inaccurate. They are off by differing amounts and suddenly will catch up. With today's GPS units, they likely can get them more accurate than ever.
On Tue, 30 Jan 2007 21:30:15 GMT, Michael Press <[email hidden]>
Quoted message said:
One way to improve the method is to put masking tape on the wheel, a piece of tape on the ground, match the edges of the masking tape exactly, roll out, then have your laboratory assistant put a piece of tape on the ground to match the registration edge of the tape on the wheel.
You have to be sitting on and/or riding the bicycle.
This works even better if you do it for more than one revolution.. For instance measure out and do it for ten revs.. I have a measured 100 feet on the road in front of my house and by counting the revs to the nearest turn, I can reduce the possible error even further..
Find mile markers and use them. I have a stretch of about 8 miles w/ markers every mile. If the computer says you've done more than a mile when you hit the marker increase circumference. You can get it so you can pick a tire model/size, consider the pressure (I vary according to type of ride, and whether I'm sore) and the tire wear and know exactly how to set the computer. My computer measures by 1/100'th, and in 8 miles I can set it so I'm within about 2/100'ths mile, which is what, about 2/800'th (=.0025) or about .25% accuracy
At some point you have to ask whether you're interested in how far you ride, or how many miles the road goes. You're going to sway a little as you pedal, and that will add up. I prefer a downhill measured route, figuring there's less chance for me to add distance on the measurement that's not on the road. OTOH, if you're looking at cue sheets on a ride, you need to match road distance for some average of coasting and pedalling. On the Other other hand, I guess you really want to match the odometer of whoever made up the cue sheets, or his or her mapping software, and at that level, you may as well throw a dart at the calibration chart that came with your computer.
