Real Mileage vs Mapped

[Chrisc]

So, did you have someone to lean against as you rolled forward? I reckon 99% of people do it the easy way (if they do it at all) and roll the bike as they walk alongside it.

No I sat on the bike and rolled forward in a straight line starting with the valve stem above a line on the floor, marked where the valve stem stopped after one revolution and measured the distance. Cateye charts suggest using 2096 for my tyre, actual rollout distance is 2102 and the circumference of the tyre measured with the wheel off the bike is 2130.

 

[ColinJ]

So the error by measuring with you off the bike is about 4 times what it would be by just taking the number from the Cateye chart!

Now the next question - did you just measure it once or did you do it several times and see what variation you got?

I think I would do it 5-10 times. If the numbers were vastly different every time, I'd rather go by the chart. If they were close, I'd take the average of them.

TBH - when I last used a computer I was happy to go with the chart. I wasn't too bothered if the numbers were half a percent or so out.

 

[Chrisc]

3 times. All the same. When I fitted the new tyres I used a strip of masking tape on the sidewall to get a more accurate measurement with it being closer to the floor. New tyres roll 2mm further than the old ones, probably due to me putting more air in so allowing less of a squish. Just realised that to be utterly anal about this you'd have to recalibrate as you lose weight....
The chart is only actually 0.28% off actual so it makes no difference in practice.