Cateye cordless 7 accuracy

[Brian Wakem]

I have a couple of regular off-road routes that I do at night on my mountain
bike. Bizarrely the distance of each course seems to be getting
progressively shorter.

Route 1 distances - ordered by date

17.73m
17.71m
17.40m
17.42m
17.17m


Route 2 distances - ordered by date

12.59m
12.48m
12.40m
12.40m
12.41m
12.38m
12.22m
12.24m
12.26m
12.22m
12.25m
12.25m
12.24m


I am 100% sure I am doing the same routes each time as I know the woods like
the back of my hand.

Anybody have any clue as to what might be going on here?


--
Brian Wakem

 

[Tim Hall]

On Thu, 06 Jan 2005 20:40:18 +0000, Brian Wakem <[email protected]> wrote:

>I have a couple of regular off-road routes that I do at night on my mountain
>bike. Bizarrely the distance of each course seems to be getting
>progressively shorter.
>
>Anybody have any clue as to what might be going on here?


Tyres getting softer, thereforereducing the effective circumference of
the wheel, therefore reducing the distance recorded?

(Goes to do sums)

Hmm, or possibly the other way round.


Tim

 

[David Martin]

On 6/1/05 8:40 pm, in article [email protected], "Brian Wakem"
<[email protected]> wrote:

> I have a couple of regular off-road routes that I do at night on my mountain
> bike. Bizarrely the distance of each course seems to be getting
> progressively shorter.
>
> Route 1 distances - ordered by date
>
> 17.73m
> 17.71m
> 17.40m
> 17.42m
> 17.17m
>
>
> Route 2 distances - ordered by date
>
> 12.59m
> 12.48m
> 12.40m
> 12.40m
> 12.41m
> 12.38m
> 12.22m
> 12.24m
> 12.26m
> 12.22m
> 12.25m
> 12.25m
> 12.24m
>
>
> I am 100% sure I am doing the same routes each time as I know the woods like
> the back of my hand.
>
> Anybody have any clue as to what might be going on here?
>

You are cutting the corners tighter.
You are going faster so less low speed wobble.
You are pumping the tyres up.
As the planet cools down it is shrinking.

...d

 

[Mark Thompson]

> (Goes to do sums)
>
> Hmm, or possibly the other way round.

What about rider getting lighter?

Either recalibrate cycle computer from time to time or eat more pies.

 

[Richard Bates]

On Thu, 06 Jan 2005 20:40:18 +0000, Brian Wakem <[email protected]> wrote:

>I have a couple of regular off-road routes that I do at night on my mountain
>bike. Bizarrely the distance of each course seems to be getting
>progressively shorter.
>Anybody have any clue as to what might be going on here?

Are you travelling at or near the speed of light?

--
Amazon: "If you are interested in 'Asimov's I-Robot',
you may also be interested in 'Garfield - The Movie'.
... erm, how do they figure that one out?

 

[Tim Hall]

On Thu, 06 Jan 2005 22:16:34 +0000, Richard Bates
<[email protected]> wrote:

>On Thu, 06 Jan 2005 20:40:18 +0000, Brian Wakem <[email protected]> wrote:
>
>>I have a couple of regular off-road routes that I do at night on my mountain
>>bike. Bizarrely the distance of each course seems to be getting
>>progressively shorter.
>>Anybody have any clue as to what might be going on here?
>
>Are you travelling at or near the speed of light?

"No, but I know where I am."


Tim

 

[Simon Brooke]

in message <[email protected]>, Brian Wakem
('[email protected]') wrote:

> I have a couple of regular off-road routes that I do at night on my
> mountain
> bike. Bizarrely the distance of each course seems to be getting
> progressively shorter.
>
[Snip: reducing distances]
>
> I am 100% sure I am doing the same routes each time as I know the
> woods like the back of my hand.
>
> Anybody have any clue as to what might be going on here?

You're picking better lines and riding more smoothly?

--
[email protected] (Simon Brooke) http://www.jasmine.org.uk/~simon/

;; no eternal reward will forgive us now for wasting the dawn.
;; Jim Morrison

 

[David Barnes]

"Brian Wakem" <[email protected]> wrote in message
news:[email protected]...
>I have a couple of regular off-road routes that I do at night on my
>mountain
> bike. Bizarrely the distance of each course seems to be getting
> progressively shorter.
>
> Route 1 distances - ordered by date
>
> 17.73m
> 17.71m
> 17.40m
> 17.42m
> 17.17m
>
>
> Route 2 distances - ordered by date
>
> 12.59m
> 12.48m
> 12.40m
> 12.40m
> 12.41m
> 12.38m
> 12.22m
> 12.24m
> 12.26m
> 12.22m
> 12.25m
> 12.25m
> 12.24m
>
>
> I am 100% sure I am doing the same routes each time as I know the woods
> like
> the back of my hand.
>
> Anybody have any clue as to what might be going on here?
>
>
> --
> Brian Wakem
>

When the battery runs down the accuracy gets iffy. Is it likely that the
battery might be running down? Try switching the batteries, in the sending
and receiving units to see if that has any effect. I found when the battery
in the sender was no longer working it was still perfectly good enough for
the receiver so I just switched the batteries round. Also found that the
readings became very iffy in the last few rides before the sender battery
gave up the ghost.

Cheers,
Dave

 

[Paul Rudin]

Brian Wakem <[email protected]> writes:


>
> Anybody have any clue as to what might be going on here?
>

The tyre pressure - and hence the circumference - is not constant?

 

[Mark Tranchant]

Brian Wakem wrote:
> I have a couple of regular off-road routes that I do at night on my mountain
> bike. Bizarrely the distance of each course seems to be getting
> progressively shorter.

> I am 100% sure I am doing the same routes each time as I know the woods like
> the back of my hand.
>
> Anybody have any clue as to what might be going on here?

You're wearing a rut in the route, bypassing some of the curvature of
the Earth.

Unless...does your route cross between two tectonic plates?

--
Mark.
http://tranchant.plus.com/

 

[MSeries]

Brian Wakem wrote:
> I have a couple of regular off-road routes that I do at night on my mountain
> bike. Bizarrely the distance of each course seems to be getting
> progressively shorter.
>
> Route 1 distances - ordered by date
>
> 17.73m
> 17.71m
> 17.40m
> 17.42m
> 17.17m
>
>
> Route 2 distances - ordered by date
>
> 12.59m
> 12.48m
> 12.40m
> 12.40m
> 12.41m
> 12.38m
> 12.22m
> 12.24m
> 12.26m
> 12.22m
> 12.25m
> 12.25m
> 12.24m
>
>
> I am 100% sure I am doing the same routes each time as I know the woods like
> the back of my hand.
>
> Anybody have any clue as to what might be going on here?
>
>

I don't think these things are guarenteed to be accurate to that amount
so it wouldn't surprise me if thats just the way it is inside the
devices. My best gusess would be the performance of the device including
its batteries changing with the temperature/humidity etc. I'd expect to
pay alot more money than we do for electronic devices that are
consistent to a hand full of yards everytime. Fit a third wheel with
clicks to be more consistent if you really care.

 

[Paul - xxx]

Brian Wakem composed the following;:
> I have a couple of regular off-road routes that I do at night on my
> mountain bike. Bizarrely the distance of each course seems to be getting
> progressively shorter.
>
> Route 1 distances - ordered by date
>
> 17.73m
> 17.17m

That's about, rough approximation, a 0.1 % difference in distance, over 17
miles, which is bloody good accuracy for a cycle computer, I'd say. I'd also
say you're probably picking slightly tighter lines, possibly also, as you
get to know the route better, going faster with less 'wobble', which
obviously decreases the distance travelled by the front wheel by a small
amount.

> Route 2 distances - ordered by date
>
> 12.59m
> 12.24m

I'd say similar to the first route, again bugger all change in percentage
terms of the whole distance covered, and such a small distance change might
easily be explained as above.

You don't say how long you've been travelling the route, but if you've only
recently started 'logging' it, then maybe, over a much longer timeframe, the
distance will tend to settle down to an optimum level, but that might take
weeks or more.

--
Paul ...
http://www.4x4prejudice.org/index.php
(8(!) Homer Rules ...
"A ****** is a ******, no matter what mode of transport they're using."

 

[MSeries]

Mark Thompson wrote:
>>(Goes to do sums)
>>
>>Hmm, or possibly the other way round.
>
>
> What about rider getting lighter?
>
> Either recalibrate cycle computer from time to time or eat more pies.

Even with recalibration you assume that the device IS accurate. Just
because it says 17.55 miles is no guarantee the distance IS 17.55 miles.
You need a certified device to compare it against.

 

[Brian Wakem]

"Paul - ***" <[email protected]> wrote in message
news:[email protected]...
> Brian Wakem composed the following;:
> > I have a couple of regular off-road routes that I do at night on my
> > mountain bike. Bizarrely the distance of each course seems to be
getting
> > progressively shorter.
> >
> > Route 1 distances - ordered by date
> >
> > 17.73m
> > 17.17m
>
> That's about, rough approximation, a 0.1 % difference in distance, over 17
> miles, which is bloody good accuracy for a cycle computer, I'd say.


I make it a 3% difference.


>I'd also
> say you're probably picking slightly tighter lines, possibly also, as you
> get to know the route better, going faster with less 'wobble', which
> obviously decreases the distance travelled by the front wheel by a small
> amount.


Yes tighter lines would go some way to explain the difference.



> > Route 2 distances - ordered by date
> >
> > 12.59m
> > 12.24m
>
> I'd say similar to the first route, again bugger all change in percentage
> terms of the whole distance covered, and such a small distance change
might
> easily be explained as above.
>
> You don't say how long you've been travelling the route, but if you've
only
> recently started 'logging' it, then maybe, over a much longer timeframe,
the
> distance will tend to settle down to an optimum level, but that might take
> weeks or more.


All these times were logged between Nov 22nd and Jan 6th.

--
Brian Wakem

 

[Brian Wakem]

"Mark Tranchant" <[email protected]> wrote in message
news:[email protected]...
> Brian Wakem wrote:
> > I have a couple of regular off-road routes that I do at night on my
mountain
> > bike. Bizarrely the distance of each course seems to be getting
> > progressively shorter.
>
> > I am 100% sure I am doing the same routes each time as I know the woods
like
> > the back of my hand.
> >
> > Anybody have any clue as to what might be going on here?
>
> You're wearing a rut in the route, bypassing some of the curvature of
> the Earth.
>
> Unless...does your route cross between two tectonic plates?


I'm not aware of any plate boundaries in North East Hampshire!

--
Brian Wakem

 

[Brian Wakem]

"Paul Rudin" <[email protected]> wrote in message
news:[email protected]...
> Brian Wakem <[email protected]> writes:
>
>
> >
> > Anybody have any clue as to what might be going on here?
> >
>
> The tyre pressure - and hence the circumference - is not constant?


But I'd need to be increasing the tyre pressure every time. They'd have
popped by now! The pressure is fairly constant.

--
Brian Wakem

 

[Brian Wakem]

"David Barnes" <[email protected]> wrote in message
news:[email protected]...

> When the battery runs down the accuracy gets iffy. Is it likely that the
> battery might be running down? Try switching the batteries, in the sending
> and receiving units to see if that has any effect. I found when the
battery
> in the sender was no longer working it was still perfectly good enough for
> the receiver so I just switched the batteries round. Also found that the
> readings became very iffy in the last few rides before the sender battery
> gave up the ghost.


The device is only 6 or 7 weeks old so I doubt the battery is low.

--
Brian Wakem

 

[Brian Wakem]

"Simon Brooke" <[email protected]> wrote in message
news:[email protected]...
> in message <[email protected]>, Brian Wakem
> ('[email protected]') wrote:
>
> > I have a couple of regular off-road routes that I do at night on my
> > mountain
> > bike. Bizarrely the distance of each course seems to be getting
> > progressively shorter.
> >
> [Snip: reducing distances]
> >
> > I am 100% sure I am doing the same routes each time as I know the
> > woods like the back of my hand.
> >
> > Anybody have any clue as to what might be going on here?
>
> You're picking better lines and riding more smoothly?


Yes this is the best explanation I could come up with, but a difference of
0.56 miles seems excessive to me. It's not like I was learning the route as
I have run 1000's of miles on these trails before I started cycling.

--
Brian Wakem

 

[Brian Wakem]

"David Martin" <[email protected]> wrote in message
news:BE036312.6E06%[email protected]...
> On 6/1/05 8:40 pm, in article [email protected], "Brian
Wakem"
> <[email protected]> wrote:
>
> > I have a couple of regular off-road routes that I do at night on my
mountain
> > bike. Bizarrely the distance of each course seems to be getting
> > progressively shorter.
> >
> > Route 1 distances - ordered by date
> >
> > 17.73m
> > 17.71m
> > 17.40m
> > 17.42m
> > 17.17m
> >
> >
> > Route 2 distances - ordered by date
> >
> > 12.59m
> > 12.48m
> > 12.40m
> > 12.40m
> > 12.41m
> > 12.38m
> > 12.22m
> > 12.24m
> > 12.26m
> > 12.22m
> > 12.25m
> > 12.25m
> > 12.24m
> >
> >
> > I am 100% sure I am doing the same routes each time as I know the woods
like
> > the back of my hand.
> >
> > Anybody have any clue as to what might be going on here?
> >
>
> You are cutting the corners tighter.


Probably.


> You are going faster so less low speed wobble.


Faster yes, but I wasn't going that slow enough to wobble to start with.


> You are pumping the tyres up.


No.


--
Brian Wakem

 

[Brian Wakem]

"Mark Thompson" <[email protected]> wrote in message
news:[email protected]...
> > (Goes to do sums)
> >
> > Hmm, or possibly the other way round.
>
> What about rider getting lighter?


My weight had increased from 10st 9lb before I started cycling to 11st 2lb.
Now that I have started running again (I started cycling due to a running
injury) I am back down to 10st 12lb and the routes are still getting
shorter.


> Either recalibrate cycle computer from time to time or eat more pies.

I shall measure the circumference of the front wheel again and see if it
different from what I originally inputted into the cateye.

--
Brian Wakem