Change wheel or tire size
11-28-21, 10:17 PM
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Change wheel or tire size
I'm a newbie, so please show some grace. I have an old Specialized Crossroads on my trainer. The tires are 700x38, which is not supported by Strava. It only goes up to 700x32. I am using Strava to connect with folks who ride for Bike MS and train for a sprint tri. Can I change the tires size or, if it's possible, would I need to change the wheels out for a smaller size?
11-28-21, 10:49 PM
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MOHEGIA Bike Tire,700 x 23/25C Road Bicycle Folding Replacement Tire = 20 USD... Good deal for a trainer...
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11-29-21, 10:15 AM
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I find it hard to believe that Strava would not allow the 700x38 tire size to be entered. Most every basic cycling computer since the 1980s have the ability to enter the tire's rolling circumference. That Strava would lack this option seems so lacking.
But I stay far away from those social games that current aps seem to encourage. I also will be surprised if a rider's daily mileage, as determined by a wheel driven device, can't be entered manually after each session. I'm sure those that are Strava nuts will give better advice. Andy
But I stay far away from those social games that current aps seem to encourage. I also will be surprised if a rider's daily mileage, as determined by a wheel driven device, can't be entered manually after each session. I'm sure those that are Strava nuts will give better advice. Andy
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Last edited by Andrew R Stewart; 11-29-21 at 10:18 AM.
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11-29-21, 12:23 PM
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I find it hard to believe that Strava would not allow the 700x38 tire size to be entered. Most every basic cycling computer since the 1980s have the ability to enter the tire's rolling circumference. That Strava would lack this option seems so lacking.
But I stay far away from those social games that current aps seem to encourage. I also will be surprised if a rider's daily mileage, as determined by a wheel driven device, can't be entered manually after each session. I'm sure those that are Strava nuts will give better advice. Andy
But I stay far away from those social games that current aps seem to encourage. I also will be surprised if a rider's daily mileage, as determined by a wheel driven device, can't be entered manually after each session. I'm sure those that are Strava nuts will give better advice. Andy
There have been times that Garmin and others I've used didn't have my size tire in the tables they give you to choose a calibration factor. However they have always allowed any value for the circumference to be entered even if it's not in the table.
For the OP.... Is this Strava App or what ever the OP is using different in that respect?
11-29-21, 12:52 PM
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To tangent slightly and end up with a better understanding of Strava I ask this- How does Strava acquire the basic distance traveled data? I believe the ap has no direct ability to determine this but requires the distance to be imported from some other device, correct? So either some sort of wheel counter is needed (spoke mag and sensor on frame/fork) or a GPS sourced distance device to provide the ap the date. Correct or not?
IF the ap is getting the distance data from another device that uses a wheel mag then it's that device that needs the tire size calibration. If the data comes from a GPS device than The wheel size in Strava is moot. If either of these two possibilities are correct Strava's tire size might be more about what you are riding and not how many wheel rotations is in a mile. Andy
IF the ap is getting the distance data from another device that uses a wheel mag then it's that device that needs the tire size calibration. If the data comes from a GPS device than The wheel size in Strava is moot. If either of these two possibilities are correct Strava's tire size might be more about what you are riding and not how many wheel rotations is in a mile. Andy
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11-29-21, 12:58 PM
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To tangent slightly and end up with a better understanding of Strava I ask this- How does Strava acquire the basic distance traveled data? I believe the ap has no direct ability to determine this but requires the distance to be imported from some other device, correct? So either some sort of wheel counter is needed (spoke mag and sensor on frame/fork) or a GPS sourced distance device to provide the ap the date. Correct or not?
IF the ap is getting the distance data from another device that uses a wheel mag then it's that device that needs the tire size calibration. If the data comes from a GPS device than The wheel size in Strava is moot. If either of these two possibilities are correct Strava's tire size might be more about what you are riding and not how many wheel rotations is in a mile. Andy
IF the ap is getting the distance data from another device that uses a wheel mag then it's that device that needs the tire size calibration. If the data comes from a GPS device than The wheel size in Strava is moot. If either of these two possibilities are correct Strava's tire size might be more about what you are riding and not how many wheel rotations is in a mile. Andy
11-29-21, 04:14 PM
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To tangent slightly and end up with a better understanding of Strava I ask this- How does Strava acquire the basic distance traveled data? I believe the ap has no direct ability to determine this but requires the distance to be imported from some other device, correct? So either some sort of wheel counter is needed (spoke mag and sensor on frame/fork) or a GPS sourced distance device to provide the ap the date. Correct or not?
IF the ap is getting the distance data from another device that uses a wheel mag then it's that device that needs the tire size calibration. If the data comes from a GPS device than The wheel size in Strava is moot. If either of these two possibilities are correct Strava's tire size might be more about what you are riding and not how many wheel rotations is in a mile. Andy
IF the ap is getting the distance data from another device that uses a wheel mag then it's that device that needs the tire size calibration. If the data comes from a GPS device than The wheel size in Strava is moot. If either of these two possibilities are correct Strava's tire size might be more about what you are riding and not how many wheel rotations is in a mile. Andy
It is possible to set this function to automatic with most devices. If you can watch the data screen, you'll see the wheel diameter vary a bit depending on signal resolution. But the average over any given time will cluster around a central value.
Op: Use that value. Most apps/devices have a place to manually enter it. Usually it is a 4 digit number of millimeters. That number is the value that the proxy "700x38" in the drop down menu is trying to establish.
Last edited by base2; 11-29-21 at 04:19 PM.
11-29-21, 04:50 PM
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Thanks for the explanations. What I didn't expect is that there is an averaging between the wheel sourced distance and the GPS derived one.
I have just recently begun to use Ride With GPS to save my bike ride routes and have noted there's about a few % difference between it and my well calibrated Cat Eye computer (I had a measured mile to do this actual distance calibration on a few years ago). Andy (still riding with no one knowing where I've gone or how slow I got there)
I have just recently begun to use Ride With GPS to save my bike ride routes and have noted there's about a few % difference between it and my well calibrated Cat Eye computer (I had a measured mile to do this actual distance calibration on a few years ago). Andy (still riding with no one knowing where I've gone or how slow I got there)
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11-30-21, 04:00 AM
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thanks for the explanations. What i didn't expect is that there is an averaging between the wheel sourced distance and the gps derived one.
I have just recently begun to use ride with gps to save my bike ride routes and have noted there's about a few % difference between it and my well calibrated cat eye computer (i had a measured mile to do this actual distance calibration on a few years ago). Andy (still riding with no one knowing where i've gone or how slow i got there)
I have just recently begun to use ride with gps to save my bike ride routes and have noted there's about a few % difference between it and my well calibrated cat eye computer (i had a measured mile to do this actual distance calibration on a few years ago). Andy (still riding with no one knowing where i've gone or how slow i got there)
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11-30-21, 12:20 PM
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Even same sized tires could have different circumferences. Does this not accept user inputted tire circumference? Even my cheap $20 Sigma accepted circumference in mm.
To measure tire circumference, 1) Mark tire. 2) place mark at ground (say the valve stem) set metric tape measure to mark starting at 0. 3) sit on bike 4) roll forward until the mark rolls around and comes back to ground. 5) measure length from 0 to Mark in mm.
I would not be changing tires just because my computer wouldn't accept my old ones...
To measure tire circumference, 1) Mark tire. 2) place mark at ground (say the valve stem) set metric tape measure to mark starting at 0. 3) sit on bike 4) roll forward until the mark rolls around and comes back to ground. 5) measure length from 0 to Mark in mm.
I would not be changing tires just because my computer wouldn't accept my old ones...
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11-30-21, 01:01 PM
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Also the difference in the circumference of a 38 and 32 mm wide 700C tire is only going to be about 37 millimeters. While that seems like a lot, that's only a 1.7% that the distance will be off.
IMO, wanting less than 7 to 5 percent accuracy is really bordering on mental sickness. But perhaps I'm too relaxed in my demands for perfection. <grin>
IMO, wanting less than 7 to 5 percent accuracy is really bordering on mental sickness. But perhaps I'm too relaxed in my demands for perfection. <grin>
