bicycle computer showing incorrect/no speed

[Ted]

I recently had a sigma BC 1200 computer installed on my bike. I bought it
and paid for installation at a reputable bike shop. On the 15km ride home
everything appeared to work, but the next day I took my bike out for a short
ride and immediately noticed that the display was showing my speed at either
below my speed (half, a third etc) or at 0kmh. When the bike is stationary
I can spin the wheel and the speed will usually show what I'm guessing is
the correct speed. The next ride I was getting 0kmh most of the time, other
than right turns. I'm thinking that the right turns moving the magnet
slightly closer.. Anyway in the manual in does say that the magnet should
be 5mm max. from the sensor/switch. The closest it reaches is about 8mm.
Is this the likely cause? I would usually trust the manual, but I'd also
like to think I can trust this bike shop.. What do you think? btw the
computer has not been exposed to any rain.

Thanks, Ted

 

[endroll]

I recently had a sigma BC 1200 computer installed on my bike. I bought it
and paid for installation at a reputable bike shop. On the 15km ride home
everything appeared to work, but the next day I took my bike out for a short
ride and immediately noticed that the display was showing my speed at either
below my speed (half, a third etc) or at 0kmh. When the bike is stationary
I can spin the wheel and the speed will usually show what I'm guessing is
the correct speed. The next ride I was getting 0kmh most of the time, other
than right turns. I'm thinking that the right turns moving the magnet
slightly closer.. Anyway in the manual in does say that the magnet should
be 5mm max. from the sensor/switch. The closest it reaches is about 8mm.
Is this the likely cause? I would usually trust the manual, but I'd also
like to think I can trust this bike shop.. What do you think? btw the
computer has not been exposed to any rain.

Thanks, Ted

I have the same comp. Mine sits about 2mm...I just checked! It's wrapped around an aero shaped carbon fork without any problems. I sometimes have to fiddle with it if I have pulled my wheel off - you should bring it closer. I noticed that my sensor stops working if it moves too far from the wheel magnet.

Let me know if you can figure it out.

 

[Bleve]

Ted wrote:
> I recently had a sigma BC 1200 computer installed on my bike. I bought it
> and paid for installation at a reputable bike shop.


My new bike has a BC1200 as well, nice little unit. But, the
magnet in the sender is pissweak. I replaced mine with a decent
magnet, and it works fine with around 3mm clearance. That said, you
probably don't need the bigger magnet (the supplied magnet wouldn't fit
on
bladed spokes properly, and I knew it to be pissweak when it
wouldn't work on the bike that I swapped the magnet from).

The Sigma sensors are mounted with rubber bands that are (reasonably!)
easy to move, you can rotate the sender around your fork (assuming it's
on
the front fork) to bring it closer to the magnet. Around 3mm or so
should give you more than enough leeway for standing sprint efforts to
not
foul the magnet, and also to deal with fitting the wheel in a hurry.




On the 15km ride home
> everything appeared to work, but the next day I took my bike out for a short
> ride and immediately noticed that the display was showing my speed at either
> below my speed (half, a third etc) or at 0kmh. When the bike is stationary
> I can spin the wheel and the speed will usually show what I'm guessing is
> the correct speed. The next ride I was getting 0kmh most of the time, other
> than right turns. I'm thinking that the right turns moving the magnet
> slightly closer.. Anyway in the manual in does say that the magnet should
> be 5mm max. from the sensor/switch. The closest it reaches is about 8mm.
> Is this the likely cause? I would usually trust the manual, but I'd also
> like to think I can trust this bike shop.. What do you think? btw the
> computer has not been exposed to any rain.

It's easy to miss-set the clearance, especially if it works in
the shop. It's not so much a matter of trust, as it's a minor
tuning issue. If they didn't set the torque right on your pedals,
I'd be worried, but if the computer sender is a few mm out but works
in the shop, that's a pretty minor thing.

 

[Ted]

> Ted wrote:
>> I recently had a sigma BC 1200 computer installed on my bike. I bought
>> it
>> and paid for installation at a reputable bike shop.
>
>
> My new bike has a BC1200 as well, nice little unit. But, the
> magnet in the sender is pissweak. I replaced mine with a decent
> magnet, and it works fine with around 3mm clearance.


Thanks for the quick responses endroll and bleve. Yeah I go it to about
3mm, but still no good.. The display is still nice and clear, no sign of a
weak battery. I might have to ride it in and get it looked at.. The magnet
is magnetised, although like you said bleve, it does feel weak (although
i've never used a bike comp. before so I don't have any others to test it
with.. I suppose that might be the next thing to try) Anyway thanks again

 

[endroll]

> Ted wrote:
>> I recently had a sigma BC 1200 computer installed on my bike. I bought
>> it
>> and paid for installation at a reputable bike shop.
>
>
> My new bike has a BC1200 as well, nice little unit. But, the
> magnet in the sender is pissweak. I replaced mine with a decent
> magnet, and it works fine with around 3mm clearance.


Thanks for the quick responses endroll and bleve. Yeah I go it to about
3mm, but still no good.. The display is still nice and clear, no sign of a
weak battery. I might have to ride it in and get it looked at.. The magnet
is magnetised, although like you said bleve, it does feel weak (although
i've never used a bike comp. before so I don't have any others to test it
with.. I suppose that might be the next thing to try) Anyway thanks again

this might be stating the obvious but does the magnet pass the centre of the sensor?
also, is the magnet parallel to the sensor?

sorry, can't think of anything else - it's not windows based so cant be a virus hehehehe

 

[NoZX6R]

Ted wrote:
> I recently had a sigma BC 1200 computer installed on my bike. I bought it
> and paid for installation at a reputable bike shop. On the 15km ride home
> everything appeared to work, but the next day I took my bike out for a short
> ride and immediately noticed that the display was showing my speed at either
> below my speed (half, a third etc) or at 0kmh. When the bike is stationary
> I can spin the wheel and the speed will usually show what I'm guessing is
> the correct speed. The next ride I was getting 0kmh most of the time, other
> than right turns. I'm thinking that the right turns moving the magnet
> slightly closer.. Anyway in the manual in does say that the magnet should
> be 5mm max. from the sensor/switch. The closest it reaches is about 8mm.
> Is this the likely cause? I would usually trust the manual, but I'd also
> like to think I can trust this bike shop.. What do you think? btw the
> computer has not been exposed to any rain.
>
> Thanks, Ted
>
>

I've used Sigmas for years now and in the past I've had at least one
which started displaying about half the real speed. It would either
diplay the speed correctly or about half of what I thought was right.

A new battery fixed the problem, despite the display never fading at
all. A battery only costs a couple of bucks so it might be worth a try.
Or take it back to the shop and get a new battery or a new unit.

Oh, and I agree with Bleve about getting a better magnet. Forget what
the manual says - put the magnet as close as you can and make sure it
lines up with the markings on the sensor.

--
Nick

 

[Ted]

"endroll" <[email protected]> wrote in message
news:[email protected]...
>
> Ted Wrote:
>>
>> > Ted wrote:
>> >> I recently had a sigma BC 1200 computer installed on my bike. I
>> bought
>> >> it
>> >> and paid for installation at a reputable bike shop.
>> >
>> >
>> > My new bike has a BC1200 as well, nice little unit. But, the
>> > magnet in the sender is pissweak. I replaced mine with a decent
>> > magnet, and it works fine with around 3mm clearance.
>>
>>
>> Thanks for the quick responses endroll and bleve. Yeah I go it to about
>> 3mm, but still no good.. The display is still nice and clear, no sign
>> of a
>> weak battery. I might have to ride it in and get it looked at.. The
>> magnet
>> is magnetised, although like you said bleve, it does feel weak
>> (although
>> i've never used a bike comp. before so I don't have any others to test
>> it
>> with.. I suppose that might be the next thing to try) Anyway thanks
>> again
> this might be stating the obvious but does the magnet pass the centre
> of the sensor?
> also, is the magnet parallel to the sensor?
>
> sorry, can't think of anything else - it's not windows based so cant be
> a virus hehehehe
>
>
> --
> endroll
>
Yeah the magnet is pretty much centred and parallel.. Before I went to bed
last night (only 4 hours ago!!) I couldn't get even a single rotation to
register. Not only was it not showing a speed, but it wasn't even adding
second to the 'ridetime' meaning that it wasn't detecting any wheel spins.
I had a listen to the sensor and I could here it very quietly make a noise
on each rotation, so the magnet seemed to be activating the switch. Could
it be not activating it enough? Or is that not possible? I know very
little about how it works.. Anyway, this morning I just gave it a spin and
it seems fine. I am about to ride to work so I'll have to see how that
goes - I'm not 'counting' on it to work though, hahaha...... yeah i just
up... That wasn't even slightly funny was it? Ah well. Previously I had
managed to get it to show a speed when rotating the wheel with a stationary
bike but not when riding.. Makes no 'SENSE'!!! I'm full of 'em this
morning. Anyway that's enough for now. It seems a great morning for riding
in Melbourne, so see some of you out there.

Ted

 

[Ted]

"NoZX6R" <[email protected]> wrote in message
news:[email protected]...
> Ted wrote:
>> I recently had a sigma BC 1200 computer installed on my bike. I bought
>> it and paid for installation at a reputable bike shop. On the 15km ride
>> home everything appeared to work, but the next day I took my bike out for
>> a short ride and immediately noticed that the display was showing my
>> speed at either below my speed (half, a third etc) or at 0kmh. When the
>> bike is stationary I can spin the wheel and the speed will usually show
>> what I'm guessing is the correct speed. The next ride I was getting 0kmh
>> most of the time, other than right turns. I'm thinking that the right
>> turns moving the magnet slightly closer.. Anyway in the manual in does
>> say that the magnet should be 5mm max. from the sensor/switch. The
>> closest it reaches is about 8mm. Is this the likely cause? I would
>> usually trust the manual, but I'd also like to think I can trust this
>> bike shop.. What do you think? btw the computer has not been exposed to
>> any rain.
>>
>> Thanks, Ted
>
> I've used Sigmas for years now and in the past I've had at least one which
> started displaying about half the real speed. It would either diplay the
> speed correctly or about half of what I thought was right.
>
> A new battery fixed the problem, despite the display never fading at all.
> A battery only costs a couple of bucks so it might be worth a try. Or take
> it back to the shop and get a new battery or a new unit.
>
> Oh, and I agree with Bleve about getting a better magnet. Forget what the
> manual says - put the magnet as close as you can and make sure it lines up
> with the markings on the sensor.
>
> --
> Nick

Thanks Nick, I was thinking the display would be noticable if the battery
was dying - When I go to the shop I'll get them to replace it. (If that's
the problem) Even if it's only worth a few dollars I want it for free!
After all I paid for it with a battery.. Anyway, thanks.

 

[Marx SS]

Mine shows a variation in the speed, but that mostly happens when I'm applying the brakes or out of the saddle.

Weak magnet. My Sigma (dunno which thou) I replaced it's magnet for a larger one gluing it to the orginal magnet spoke mount. Clearence between the magnet & sensor is a bee's bob.
After countless offs MTBing in all sorts of conditions it's still sending 100%.

I found that the rubberband mount for the actual unit is a brain wave, seems that my bike comp is the last thing to get damaged now as a result of a stack.

 

[Zoom]

Ted wrote:
>>Ted wrote:
>>
>>>I recently had a sigma BC 1200 computer installed on my bike. I bought
>>>it
>>>and paid for installation at a reputable bike shop.
>>
>>
>>My new bike has a BC1200 as well, nice little unit. But, the
>>magnet in the sender is pissweak. I replaced mine with a decent
>>magnet, and it works fine with around 3mm clearance.
>
>
>
> Thanks for the quick responses endroll and bleve. Yeah I go it to about
> 3mm, but still no good.. The display is still nice and clear, no sign of a
> weak battery. I might have to ride it in and get it looked at.. The magnet
> is magnetised, although like you said bleve, it does feel weak (although
> i've never used a bike comp. before so I don't have any others to test it
> with.. I suppose that might be the next thing to try) Anyway thanks again
>
>

Try changing the height a bit. The sensors often have a small piece of
iron in them that helps to concentrate the magnetic force onto the reed
switch (located in the sensor). Often there will be a mark on the sensor
which is what the magnet has to line up with. Experiment with the height
a bit.

Zoom

 

[aeek]

ride and immediately noticed that the display was showing my speed at either
below my speed (half, a third etc) or at 0kmh. When the bike is stationary
I can spin the wheel and the speed will usually show what I'm guessing is
the correct speed. The next ride I was getting 0kmh most of the time, other
than right turns. I'm thinking that the right turns moving the magnet
slightly closer.

Which spoke is the magnet on, over/under? That is a 2mm difference.
Is the magnet or sensor moving? Tighten, or add some padding.

 

[BruceA]

Ted

Sounds like a magnet problem, but there is something else you can try.
I have also found similar problems with zero and incorrect speed readings
being due to a dodgy connection between the contacts on the computer and the
base that it clips into (even with a new computer). Try cleaning the
contacts and see if this makes any difference. I am not sure of the best
way to clean the contacts, but I use one of those course rubbers (I think
they are meant for erasing pen marks) to remove any fine layer of oil,
grease or minor corrosion. Sometimes just jiggling the computer when it
stops working will bring it back to life.


BruceA

 

[tony f]

"BruceA" <[email protected]> wrote in message
news:[email protected]...
> Ted
>
> Sounds like a magnet problem, but there is something else you can try.
> I have also found similar problems with zero and incorrect speed readings
> being due to a dodgy connection between the contacts on the computer and
the
> base that it clips into (even with a new computer). Try cleaning the
> contacts and see if this makes any difference. I am not sure of the best
> way to clean the contacts, but I use one of those course rubbers (I think
> they are meant for erasing pen marks) to remove any fine layer of oil,
> grease or minor corrosion. Sometimes just jiggling the computer when it
> stops working will bring it back to life.

I use electrical contact cleaner.

Ted can hear the reed switch working, so the magnet should be OK, but he
could test the head contacts with a multimeter. Ummm - use the resistance
mode, and the meter should go to zero each time the circuit is completed,
and back to one when the circuit is open (electricians feel free to correct
me!). My understanding is it's completing the circuit that activates speed
(etc) recording - it should close (complete) once per wheel revolution.

Despite that, my experience has been that the magnet position is generally
the most crucial part of the circuit, although I have had dodgy wires and
head contacts - but not on a new one. Oh yes, and having the speedo fly off
at speed never helps... ;^)

HTH

Tony F
www.thefathippy.com

 

[TimC]

On 2005-08-09, Ted (aka Bruce)
was almost, but not quite, entirely unlike tea:
> Yeah the magnet is pretty much centred and parallel.. Before I went to bed
> last night (only 4 hours ago!!) I couldn't get even a single rotation to
> register. Not only was it not showing a speed, but it wasn't even adding
> second to the 'ridetime' meaning that it wasn't detecting any wheel spins.
> I had a listen to the sensor and I could here it very quietly make a noise
> on each rotation, so the magnet seemed to be activating the switch. Could
> it be not activating it enough? Or is that not possible?

The little reed switches used are an all or nothing thing. If it
makes a click, then yes it is being triggered, so there must be a
break in the wire or other connection.

I can't imagine how an intermittent connection or wire would make and
break in such a way as to register every second or third rotation
though

--
TimC
So y'know, when the girl octopus slaps the boy octopus for being too
forward, he could say it wasn't his fault, the arm just kind of did its
own thing. -- Kasatka in AFAFDA

 

[TimC]

On 2005-08-09, Marx SS (aka Bruce)
was almost, but not quite, entirely unlike tea:
>
> Mine shows a variation in the speed, but that mostly happens when I'm
> applying the brakes or out of the saddle.
>
> Weak magnet. My Sigma (dunno which thou) I replaced it's magnet for a
> larger one gluing it to the orginal magnet spoke mount. Clearence
> between the magnet & sensor is a bee's bob.

My magnet and sensor seem to be quite well coupled, despite them
having plenty of clearance.

> After countless offs MTBing in all sorts of conditions it's still
> sending 100%.
>
> I found that the rubberband mount for the actual unit is a brain wave,
> seems that my bike comp is the last thing to get damaged now as a
> result of a stack.

I like it, although they are damn fiddly to get on, and the mount for
the actual display seems far too flimsy; I am waiting to break off one
of the slotted things as I try to move it around.

--
TimC
> Bugger you guys.
> The babelfish is idempotent on the set above.
I'm afraid that isn't a very good pickup line either, Tim. - MaryG