Help Setting Up Cycle Computer

chrisb1357

Über Member
Hi all,

I have a Raleigh 16 Function cycle computer which i have the userguide for as well but i cannot work out what wheel size i should input into the computer. How do i work this out.

I have been on a few sites to work out but cannot seem to get the same answers

Chris
 

Octet

Veteran
You probably shall want to put in the radius, then the computer shall do a 2 * Pie * R to work out the circumference.
So you shall want to measure from the bottom of the tyre up to the centre.
 

fossyant

Ride It Like You Stole It!
Location
South Manchester
2096 is standard 700c 23mm

Measure by having valve at bottom, mark floor, roll bike forward (best sit on it) 1 revolution, and measure the distance.

Usually entered as mm or cm - eg 2096mm would be 210cm
 
OP
C

chrisb1357

Über Member
Ahh ok so as easy as that.

Also my next question is how far down the spoke from the tyre should the sensor be placed on the spoke.
 

Octet

Veteran
My mistake, sorry :shy:

It does use the circumference, I did the 2 * Pie * R on a calculator as it was easier then measuring it and then entered it.
 

TheDoctor

Europe Endless
Moderator
Location
Stevenage
I've done that. It's close enough for most uses.
You don't really need to know the distance to the pub to the nearest metre, after all...
 
OP
C

chrisb1357

Über Member
Yes my computer is wireless so as near to the top of the wheel/tyre

Does changing the distance on where the sensor is have any affect on the speed etc which is picks up. i.e near the centre will spin faster and slow the further up the spoke you go or have i got this wrong LOL

Chris
 

snorri

Legendary Member
Mine used the radius, almost sure it did... probably should check that :unsure:
Nothing wrong with using the radius method, you would have probably come up with the same end result.:smile:
However some of us use a modified fossyant method and put a generous chalk mark on the tyre tread, sit on the bike and roll it forward for one full revolution, plus a bit, of the wheel. Then measure the distance between the two chalk marks which have been transferred off the tyre to the floor.
The sensor is simply recording the passing of the magnet on the wheel spoke and sending a pulse up to the computer. The magnet can only pass the sensor once for every revolution of the wheel so the positioning of the magnet on the spoke will not affect the working of the computer.
 

snorri

Legendary Member
Apparently it doesn't, I have never gotten my head around why it doesn't but hey ho.
The speed at which the magnet passes the sensor is irrelevant. The computer measures the number of pulses it receives from the sensor in a given time.
If the wheel turns 90 times in one minute, then the computer will receive 90 pulses in a minute and display a speed of X mph, if the wheel turns 180 times per min., computer receives 180 pulses in a minute and will indicate 2X mph
 
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