# Cycle Computer - Does the magnet matter?



## punkypossum (13 Mar 2008)

I'm having problems with the magnet holder thingy on my current cycle computer, it's a really weird clip on design and the magnet keeps moving. So, I was wondering if I could take it off and stick on the magnet from my old computer which is the good old traditional screw to spoke design. I don't want to take the current one off to test this, as the thing is so flimsy it would probably not survive being taken off or put on again. Does anybody know if this would work? Are all magnets basically the same no matter what make the computer is?

Any advice highly appreciated!


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## Stig-OT-Dump (13 Mar 2008)

I doubt it would matter at all, but there may be polarity issues, SO why not experiment.

Walk your bike along at a steady pace (say 3mph or just enough for your computer to register). Then put your extra magnet on a spoke that is on the opposite side of the wheel (6o'clock vs 12 o'clock, not left vs right) and walk along at around the same pace. If the spare magnet works you'll register a speed going at a dead slow walk, or you'll appear to be walking at 6mph, when walking at 3mph. Then you can take off the flimsy new magnet and go back to a true speed of 3mph. If it stays at 3mph throughout, your old magnet won't work, but it'll be easy to remove cos it is traditionally built.

Right, I'm off to polish my elbow patches...


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## domtyler (13 Mar 2008)

Some do, some don't. Seems pretty random to me.

I have a GPS based one now anyway, magnets are just so last year!


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## bonj2 (13 Mar 2008)

punkypossum said:


> I'm having problems with the magnet holder thingy on my current cycle computer, it's a really weird clip on design and the magnet keeps moving. So, I was wondering if I could take it off and stick on the magnet from my old computer which is the good old traditional screw to spoke design. I don't want to take the current one off to test this, as the thing is so flimsy it would probably not survive being taken off or put on again. Does anybody know if this would work? Are all magnets basically the same no matter what make the computer is?
> 
> Any advice highly appreciated!



Basically, yes - but there may be polarity issues like someone else says.
The side effects of that could be that it will think you are going backwards, and read MINUS whatever speed it is you're going. You could solve this by just putting your wheel on the other way round, or just ignoring the minus sign if it doesn't bother you. As long as YOU know you're going forwards, that's the main thing.

Also make sure you use a magnet that's designed for bike computers and not a normal hosuehold magnet, as it could be too strong and pull your wheel over to that side, and/or slow you down once per revolution leading to you lurching along in a very unladylike and frankly silly manner.


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## mickle (13 Mar 2008)

Bonj is in the mentalist phase of his lunar cycle.

Punky, a magnet is a magnet. Your computer has a coil through which a small current is passed. The magnetic field causes a small change in the current every time it passes which the cycle computer recognises and counts. You told the computer how big your wheel is, the puter does the rest. A magnet is a magnet.


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## Dave5N (13 Mar 2008)

Careful, PP. Bonj is right.

Get the polarity wrong and you'll start goin' backwards. It'll be ok at first, though more hilly than expected. Soon though, it will get very wet, then green and rainy, then very very wet indeed.

Eventually, the buildings will be tall.


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## punkypossum (13 Mar 2008)




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## bonj2 (13 Mar 2008)

obviously another much easier to all this palaver is to just up sticks and move to anywhere in the southern hemisphere, it's all reversed there.


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## Dave5N (14 Mar 2008)

Yes, but it takes a little while to get used to riding upside down as well as backwards.


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## Arch (14 Mar 2008)

bonj said:


> obviously another much easier to all this palaver is to just up sticks and move to anywhere in the southern hemisphere, it's all reversed there.



no, but then she'd have to swap the drivechain over to the other side, and pedal backwards...

I just gave up on computers. If I'm going so slow I get overtaken by walkers, I give up and push and I know how far I've gone by how much I need some tea and cake....


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## Arch (14 Mar 2008)

But I'm enjoying the image of Punky riding along with a huge great cartoon horseshoe magnet strapped to her wheel...


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## Over The Hill (14 Mar 2008)

I cannot see that it will harm it to give it a try. It must only be kicking a switch device that probably works both ways as magnets can jump polarity and they would have a hard job making them all the same way round. 

Get one bit and wave it past the other as it would on the bike. If it reads it on the display then you are OK. 

If the clip is broken put it on with tape or onto one of those reflectors you clip between spokes.


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## punkypossum (15 Mar 2008)

I waved the magnet in front of the sensor - it appears to be working! In fact, I was faster waving than I usually am when riding, maybe this is the way forward!


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## Dave5N (15 Mar 2008)

Lightest way is to buy a small rare earth magnet and glue it to a spoke.

I got that top tip from weight weenies!.


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## mickle (15 Mar 2008)

If you put two magnets on you go twice as fast.


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## Dave5N (15 Mar 2008)

mickle said:


> If you put two magnets on you go twice as fast.




Thanks for the tip. I was wondering why I was finishing a lap down. That explains it. The others must've had two magnets.


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## BentMikey (16 Mar 2008)

Polarity with a reed switch? LOLOL!


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## bonj2 (16 Mar 2008)

Dave5N said:


> Lightest way is to buy a small rare earth magnet and glue it to a spoke.
> 
> I got that top tip from weight weenies!.



Why does it have to be rare? Won't a common one do?


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## alecstilleyedye (16 Mar 2008)

the sigma magnets are very light. and buggers to remove without hurting your fingers.


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## Milo (16 Mar 2008)

You might as well go to the loo before getting on the bike my magnet only ways 50 grams or so and its a cheap computer.


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## Dave5N (16 Mar 2008)

Hey! Don't shoot the messenger!


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## cicaparlez (26 Feb 2011)

After years of reading forums, this is the first one that i've registered to use. The only reason I did so is to let you all know how much I enjoyed reading the comments in this thread. You guys are awesome!!  Ta x


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## slowmotion (26 Feb 2011)

My guess is that the pick-up isn't a reed switch but a solid-state *Hall effect switch*.

See here...

http://en.wikipedia.org/wiki/Hall_effect_sensor

I've no idea if the magnet strength affects performance.

Edit: Hmmm, that might well be wrong given the need for low power consumption....


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## Norm (26 Feb 2011)

WARNING!!!! 3 YEAR OLD ZOMBIE THREAD.

Before anyone else makes the mistake that slowbie made and before someone welcomes Bonj back.


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## Sleeping Menace (26 Feb 2011)

Also.. put the magnet 180 degrees *as much as possible) from your valve stem and you'll go a ways towards putting the wheel in balance. Wheels are almost always heavier at the stem..this serves to counter that.. 

........................
http://anotherdooratthe.endoftheinternet.org

Cycle related blog entries, including a few 5 minute reviews:
http://anotherdooratthe.endoftheinternet.org/category/cycling/


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## Cubist (26 Feb 2011)

Bloody hell, welcome back Bonj and Punkypossum!


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## slowmotion (27 Feb 2011)

Can somebody talk me through this epic episode of CC lore? 

I is lost.


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## Cardiac (27 Feb 2011)

BentMikey said:


> Polarity with a reed switch? LOLOL!


Generally it's not an issue (and I perhaps never with bike computers - I am no expert on them), but _SOME_ reed switches are configured to operate in a particular way whereby they have a fixed bias magnet to create a local magnetic field, and then the north pole / south pole orientation of the moving magnet does matter. One way it will work, the other it won't.

I love the idea of two magnets to double the reading - made me chuckle.


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## Fab Foodie (27 Feb 2011)

Norm said:


> WARNING!!!! 3 YEAR OLD ZOMBIE THREAD.
> 
> Before anyone else makes the mistake that slowbie made and before someone welcomes Bonj back.




Ahhhhh, you see the prescence of bonj is felt from beyond the forum. His bonjness transcends time and space as we know it.


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## steve52 (27 Feb 2011)

i now in the shed franticly rubing a magnet along each of my spokes!!!! the idear is to magnatise each spoke!!!!! how fast will i be then?


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## screenman (27 Feb 2011)

Not only how fast but what a good tip for those wanting to lose weight. going faster burns more calories, or does it.


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## ian turner (27 Feb 2011)

Probably a spammer who resurrected a somewhat average thread too but just goes to show that 9 out of 10 cyclists don't read beyond the first before answering


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## Cardiac (27 Feb 2011)

Damn! I normally spot those before in through throw in my 2 cents. Oh well.


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## PoweredByVeg (27 Feb 2011)

steve52 said:


> i now in the shed franticly rubing a magnet along each of my spokes!!!! the idear is to magnatise each spoke!!!!! how fast will i be then?


Ha Ha Ha Ha love it!


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## Dave5N (28 Feb 2011)

steve52 said:


> i now in the shed franticly rubing a magnet along each of my spokes!!!! the idear is to magnatise each spoke!!!!! how fast will i be then?



Nice use of euphemism. Very delicately put. Well done.


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## slowmotion (28 Feb 2011)

I never was very good with dates.


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## Paulus (28 Feb 2011)

slowmotion said:


> I never was very good with dates.




Is this a first for the forum, a 2 year old topic getting revitalised by accident?


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## Norm (28 Feb 2011)

Paulus said:


> Is this a first for the forum, a 2 year old topic getting revitalised by accident?


Certainly not - and did you realise we are in 2011 now?


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## subaqua (28 Feb 2011)

OK i know its an old thread but I can get 100mph on my cycle puter if i set the cateye front light to flash . 

I think i need to separate the distance betweeen them


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