Wheel size ??
RandG
Posts: 779
It's become clear my wireless computer is quite literally miles out, which makes me suspect it's got the wrong size in it, so simple question is, what figures should I be putting in ??
Standard 3.1 Trek btw.
i.e 2024/2027 etc etc ???
It was out tonight by almost 2 miles compared to my gps tracker.
Standard 3.1 Trek btw.
i.e 2024/2027 etc etc ???
It was out tonight by almost 2 miles compared to my gps tracker.
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Comments
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Which computer do you have? The manual for mine (Sigma BC1009) has a conversion table for all main wheel sizes...0
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Put a mark on your tyre and then measure one full revolution along the ground. This distance is what you need to input0
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What's your wheel size?
Edit: You need 2096 for 700x230 -
Remove the front wheel and measure the diameter of it with a tape measure. I find the easiest way to do this is to use electrical tape to attach a steel retracting tape measure to the wheel. In theory it is slightly more accurate to mark the wheel with chalk and then roll the bike with you in the saddle to make two chalk marks and then measure the distance between.0
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richh wrote:
Possibly, but possibly not. As wirral_paul has said, you need to measure it as it will be depending and rim tolerances, different tyre spec and inflation pressures.GSJ wrote:What's your wheel size?
Edit: You need 2096 for 700x23
Well, up to a point, but even if you're looking at 20 mil (and I doubt those factors would come to anything like that) that's only a 1% difference. Would it really make any material difference if the speedo was reading 10.1MPH rather than 10.0? Or a longer ride coming in at 50.5 miles rather than 50? It's still more accurate than most car speedos/odometers.0 -
Measure it with yourself on the bike, makes a difference (albeit a small one)0
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My Garmin 500 has automatically worked my size to be 2118.
I assume it does that by using cadence and GPS speed calculations.Cube Agree GTC Pro
Boardman Comp
Carrera Subway Hybrid0 -
It would matter to me if I did what I thought was a 100 mile ride that actually ended up being only 99 miles. Yes.karlth wrote:richh wrote:
Possibly, but possibly not. As wirral_paul has said, you need to measure it as it will be depending and rim tolerances, different tyre spec and inflation pressures.GSJ wrote:What's your wheel size?
Edit: You need 2096 for 700x23
Well, up to a point, but even if you're looking at 20 mil (and I doubt those factors would come to anything like that) that's only a 1% difference. Would it really make any material difference if the speedo was reading 10.1MPH rather than 10.0? Or a longer ride coming in at 50.5 miles rather than 50? It's still more accurate than most car speedos/odometers.
Ok, so it doesn't really matter in the grand scheme of things but for the sake of two minutes with a piece of chalk there's no reason not to do it properly.0 -
richh wrote:
It would matter to me if I did what I thought was a 100 mile ride that actually ended up being only 99 miles. Yes.karlth wrote:richh wrote:
Possibly, but possibly not. As wirral_paul has said, you need to measure it as it will be depending and rim tolerances, different tyre spec and inflation pressures.GSJ wrote:What's your wheel size?
Edit: You need 2096 for 700x23
Well, up to a point, but even if you're looking at 20 mil (and I doubt those factors would come to anything like that) that's only a 1% difference. Would it really make any material difference if the speedo was reading 10.1MPH rather than 10.0? Or a longer ride coming in at 50.5 miles rather than 50? It's still more accurate than most car speedos/odometers.
Ok, so it doesn't really matter in the grand scheme of things but for the sake of two minutes with a piece of chalk there's no reason not to do it properly.
Even so, that's assuming an error of 20mm, which I doubt you're actually looking at. There's a perfectly good reason not to "do it properly" and go with a simple calculation - not worth the faff. Besides which, what are the error margins involved with chalk lines anyway? I bet it's a few mm.0 -
No. it takes distance travelled from GPS data and wheel revolutions from the speed sensor part of the GSC10. You will find that it varies a bit due to GPS wander so I would take an average of several checks and then set this as the custom setting. Or measure it as above.Ringo 68 wrote:My Garmin 500 has automatically worked my size to be 2118.
I assume it does that by using cadence and GPS speed calculations.0
