PING ALL COKEURS: Share your rollout data (Was Re: What circumference did you ent...

On Mon, 8 Sep 2003 13:49:52 -0500, johnfoss
<> wrote:

>So I’m fine with a nice, median number. That’s why I would be interested
>to hear the results people are getting, in the form of circumference
>numbers, listed along with those other factors mentioned above. If
>several people do this, the rest of us (the lazy ones) may be able to
>make pretty accurate extrapolations from that data.

Even though I don’t own a Coker yet, I volunteer to process the data
(if enough comes in) into a formula that estimates rollout from
A. rider weight,
B tyre pressure and
C tread wear (as an estimated percentage).

Please state also whether the rollout is

  1. unloaded and in a straight line, or
  2. loaded and in a straight line, or
  3. from a ridden distance so that wobble is included. You may want to
    include additional data (speed, surface type etc) but it may be

Data are best posted here (as opposed to sent via e-mail) so that they
are publicly available. The few that have been posted in this thread
need no repeat but you might want to elaborate on them.

>As for wobble, this is another factor that varys not only with the
>individual, but I think also with the speed you are riding. I’d rather
>not factor in wobble, unless it happens automatically as part of the
>calibration method.

That is stinky. That way you will have wobble in some data but not in
others, depending on how it happened to have been measured.
Contamination of the data set!

Klaas Bil - Newsgroup Addict

If the crank is moving then it really sounds as if it’s loose. - onewheeldave trying to pinpoint the cause of a clicking crank

Here’s my scientific method. I stole data from other people. I entered it into my computer. I adjusted from time to time, based on observations from other road markings and bicyclists and car odometers.
I am happy to get within 2% accuracy(I usually ere on the fast/long side). I give myself a break and don’t try to discount for wobble(I don’t wobble as much as some)

Now to answer the questions:
C:Varies from ride to ride:)

I did a rollout(unloaded) long ago and don’t remember the number
Right now I have 281 entered into my cyclometer and I’m happy with that number.


Re: PING ALL COKEURS: Share your rollout data (Was Re: What circumference did you ent…

A. rider weight 170 lb
B tyre pressure 50 psi
C tread wear (as an estimated percentage) 50
3) from a ridden distance so that wobble is included. Distance is 3
revolutions, averaged over multiple runs


2782 mm
calibrated via 0 UPD known distance 2.65 mile ride

FYI: that’s with the tire at 32psi and moderately warn down (about 1/2 of it’s life), and I weigh 150lbs

Can’t remember the exact figure I used, but my view is that a 1/2 inch error on a 36 inch diameter = 1.3%. That’s more accurate than my car speedo or scooter speedo. My weight fluctuates; the weight of water in my Camelbak fluctuates; the tyre pressure varies throughout a ride. I reckon if the tyre’s a bit softer, then the mileage and speed are ‘rounded up’, but pedalling is a bit harder, so it’s self-compensating. Then again, I only use the computer for comparing my own performances.

These rollout posts are fragmented and I don’t want my post to get lost; it’s in this thread.

Basically I argue in detail for eliminating all rider characteristics from the rollout that we share.

Because we are the nerds, not them.

Very well placed post, John! We can get pretty nerdy over a millimeter or two sometimes.

For my 2 cents worth on the rollout though…when i first fitted a computer to my coker, i did an unmounted rollout…just pushed it down the road and took a measurement. I knew it wouldn’t be very accurate, but i couldn’t figure out any way to do an accurate rollout mounted. Then i spent several days making small adjustments after riding on routes of “known” distances until the computer reading matched what i thought the distance was.

Not very scientific, i know…you’ve still got the argument of “how did you arrive at the known distance?”

Anyway, the number i arrived at was 280…my cheapo computer only accepts cm, not mm.

A man with a watch always knows what time it is… a man with two watches is never quite sure.