Halfords Cycle Computer!!!



gingermoonman

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Sep 17, 2003
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:confused: Hi can anyone help my I have a halfords cycle computer and have not used it for a while, I went to use it the other day and it did not work so I have replaced the batteries in the computer and the one on the wheel the display all works but does not register my speed etc it is almost like it can not see the wheel and I can not find the instructions has anyone got any ideas as I do not want to buy another one.
 

James Godley

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Jan 29, 2003
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Sounds a bit obvious but is the magnet close enough to the right bit of the pickup.

I'm assuming as both bits have batteries, that its a wireless system??
 

gingermoonman

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Sep 17, 2003
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I have managed to get it to work but not sure I have set wheel size right do you know how to work it out and does the magnet etc need to be on the outside of the wheel or can it be anywhere on the wheel
 

jtfleming

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Aug 9, 2003
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Wheel size is most likely expressed in millimeters. You need to find a nice open space in the driveway or basement or whatever, line up the valve so it is dead center at the bottom, mark the floor with chalk or something at that point, roll the bike forward, and when the valve is again in the same position, mark the floor again, and then measure between the two to get the distance.

Your magnet needs to be pretty close to the sensor...not more than 1/4 inch or so.
 

gingermoonman

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Sep 17, 2003
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Thanks for that does it matter where the magent/sensor is on the spokes ie near the centre or near the tyre?
 

jtfleming

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Aug 9, 2003
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no as long as it is the magnet and sensor are close, one revolution is what it is measuring
 

gingermoonman

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Sep 17, 2003
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Does it not need to be near the rim as if it was near the centre one revolution would come round quicker if it was in the centre not near the rim?? sorry about this being a bit dumb!!
 

kneighbour

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Apr 30, 2003
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Originally posted by gingermoonman
Does it not need to be near the rim as if it was near the centre one revolution would come round quicker if it was in the centre not near the rim?? sorry about this being a bit dumb!!

It does not matter where on the wheel you put the magnet. And if you think about it, it takes EXACTLY the same amount of time for the inner part of the spoke to revolve as the outer part - if this was not the case the wheel would buckle! The magnet would travel at different speeds at different points on the spoke, but it will take the same time do do one revolution as ALL parts of the wheel do.
 

DavidRM

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Apr 19, 2004
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Can anyone help, I have just purchased a Halfords 12 function Cycle Computer (item code 108407) and the wheel circumference table does not list my tyre size, which is 26 x 1.95. The nearest tyre sizes are ATB 26 x 1.75 (2045mm), 26 inch (650A) (2073mm) and ATB 26 x 20 (650B) (2099mm). Is there a way to work out which setting to use and can anyone explain what ATB, 650A and 650B are.
 

Randybaker99

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Nov 13, 2003
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Originally posted by DavidRM
I'm still looking for help with the above problem?

It might be best to just measure one rotation of your wheel on your driveway, with a tape measure. That is the most accurate method.

However, the instructions on my Astrale 8 lists 26" by 1.95" as having a circumference of 2050 mm, so you are probably safe going with that, especially since it seems to match up with the other measurements you reference.
 

DavidRM

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Apr 19, 2004
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Originally posted by Randybaker99
It might be best to just measure one rotation of your wheel on your driveway, with a tape measure. That is the most accurate method.

However, the instructions on my Astrale 8 lists 26" by 1.95" as having a circumference of 2050 mm, so you are probably safe going with that, especially since it seems to match up with the other measurements you reference.


Thanks for the information Randybaker99, I did a bit of a search and came up with 2050mm as you've suggested. So I've used this setting and have also calibrated the computer by carrying out a 10 mile measured run in a car and then following the same route by bike and it seems to be fairly accurate.
 

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