Gixxerman
Guru
- Location
- Market Rasen
I have recently bought a cycle computer (£15 from Aldi - a bargain!).
But I need to input the wheel circumference.
I have a Trek 7.3 FX with 700x32c tyres.
According to Sheldons tables, the value is 2155mm.
But I used a tape measure to measure the wheel around the fattest part of the tyre and the value I got was 2193mm.
Why is there such a big discrepency? Do the tables take into account the rolling circumference based on tyre deformation due to rider weight?
Do I need to do a rollout test to get and accurate value?
I suppose I could ride for one mile and compare it with my GPS and make adjustments accordingly.
But which to believe? Is the computer telling the truth or is GPS telling the truth?
I have 2 GPS systems so I suppose I could use them both and do a 2 from 3 vote.
But I need to input the wheel circumference.
I have a Trek 7.3 FX with 700x32c tyres.
According to Sheldons tables, the value is 2155mm.
But I used a tape measure to measure the wheel around the fattest part of the tyre and the value I got was 2193mm.
Why is there such a big discrepency? Do the tables take into account the rolling circumference based on tyre deformation due to rider weight?
Do I need to do a rollout test to get and accurate value?
I suppose I could ride for one mile and compare it with my GPS and make adjustments accordingly.
But which to believe? Is the computer telling the truth or is GPS telling the truth?
I have 2 GPS systems so I suppose I could use them both and do a 2 from 3 vote.