# Cycle Computer - Does the magnet matter?

Discussion in 'Beginners' started by punkypossum, 13 Mar 2008.

1. ### punkypossumDonut Devil

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?

2. ### Stig-OT-DumpVeteran

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...

3. ### domtylerÜber Member

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

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

4. ### bonj2Guest

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.

5. ### mickleFFS

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.

6. ### Dave5NÜber Member

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.

7. OP

8. ### bonj2Guest

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.

9. ### Dave5NÜber Member

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

10. ### ArchMarried to Night Train

Location:
Salford, UK
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....

11. ### ArchMarried to Night Train

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

12. ### Over The HillGuru

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.

13. OP

### punkypossumDonut Devil

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!

14. ### Dave5NÜber Member

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

I got that top tip from weight weenies!.

15. ### mickleFFS

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