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Just did a roll out test to measure wheel circumference and calibrate my computer. I ended up with 2083mm. My computer had been previously set to 2096mm. So have I been riding at a faster or slower speed with the computer set at 2096mm with a real circumference of 2083mm?
FWIW, I measured one revolution (stem to stem) BDC, weight on bike, and tire pressure where I plan to ride it.
At the same actual speed;
2083 = 39.75kmh
2096 = 40kmh
Is it that important ?
Anyway, the circumference will change with inflation differences etc.
Less than 5% error. By setting the computer to a greater value, it'll display a higher speed than actual.
mikesbytes said:At the same actual speed;
2083 = 39.75kmh
2096 = 40kmhIs it that important ?
Anyway, the circumference will change with inflation differences etc.
Speedwise maybe not. Distancewise YES (specially those who take pleasure in racking up mileage). The odometer may say 0.25kms (250 meters) more if it registers 40kms. That's almost 60kms. difference every 1000kms registered on the ODO.
hd reynolds said:Speedwise maybe not. Distancewise YES (specially those who take pleasure in racking up mileage). The odometer may say 0.25kms (250 meters) more if it registers 40kms. That's almost 60kms. difference every 1000kms registered on the ODO.
So I'm out by 500mtrs on a 80k ride. Must remember to finish with a lap of the block.
mikesbytes said:At the same actual speed;
2083 = 39.75kmh
2096 = 40kmhIs it that important ?
Anyway, the circumference will change with inflation differences etc.
Obviously, math and physics isn't my cup of tea. Being so, I didn't know how important the difference was. I'm aware of the importance of constant psi which is why I said I used the psi I planned to ride with...
BTW, what's the formula? I was getting hung up on S(r)=S(L)/C. Then: S(L)=S(r)*C
Thanks for the input.
Don't need no formula 13 over 2083 is .624 % positive error. Way better than your cage, but if you are going to the trouble of setting it ....
I am a little over the top anal on this. I will get some assist, and sit on the correctly inflated bike and roll 10 revolutions to get dead balls accurate - yes, I'm considering therapy.
On long motorcycle trips I will count my odo for 10 or 100 miles and compare it to the mile markers, do the math in my head for entertainment, and keep tabs on tire wear with the variance. pitiful .
I'm still deciding whether to get a blue speedo or a black speedo.
mikesbytes said:I'm still deciding whether to get a blue speedo or a black speedo.
And give up free speed ? Come on mate, everyone knows red is faster !
and it'll match your eyes:eek:
9.8mps2 said:And give up free speed ? Come on mate, everyone knows red is faster !
and it'll match your eyes:eek:
I have to agree on that
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