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Bike speedo advice


finmac

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My car has a Sigma Sport BC 800 speedo, but the head sensor unit (at the wheel end) is bust.

 

Wonder does anyone know if these are still made and where I can buy a new one, also the likely cost?

 

thanks Finlay

 

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Finlay -

 

I assume you had to cut the wire between the sensor and the computer mount to extend it anyway - in which case *any* old make/model of sensor will work.

 

If, by some miraculous bit of luck, your original cable was long-enough to stretch from the front-wheel to the cockpit - then the answer is basically the same - find any-old sensor, splice the wire and off you go...

 

I *might* have an old sensor kicking around (I've owned so many bike comps in the past) - or you could just ask at your local bikeshop for them to keep an eye out for someone who has broken their cable...

 

Or you could just go to Ribble Cycles and buy a BC1200 for about £16...

 

Keep BC free and open for ALL. Membership No. 43xx

 

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How would one go about fitting a bike speedo.

 

Do you need to have the wheel balanced after fitting the magnet jobby to the wheel.

Do you have to fit the magnet that comes with the speedo or can you fit something a little esaier to stick on a wheel.

What do you need to look for as far as features go on these things.

 

Is there an article anywhere about someone doing this.

 

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Of course there's an article...

 

One of the first things I wrote up - should probably tidy it up a bit...

 

here

 

To answer your questions:

 

i)No - not in general. I've never noticed the difference. If you are changing a tyre and plan to use that wheel in the 'sensor' position, it does make sense to have the magnet in place before fitting the tyre - but it's not really worth having the wheel rebalanced specially. (IMHO)

 

ii) I do use the magnets that come with the speedos. The Sigmas come with two - one horrible, heavy steel cased job (that has a screw-clamp thing to grab your bike spoke) and a lightweight plastic cased jobby. You can either just glue the plastic cased thing direct to the wheel, or prise the case apart and glue the magnetic inner steel cylinder to the wheel instead...

 

Or you can use small disk magnets such as those found on travel-chess pieces or in your local craft shop - I have used these, but you can never guarantee how strong they are.

 

iii)Features? You obviously want a nice, clear speed display (the Sigma BC1200 is very good and uses a higher-tech display than traditional 8-bar digits). Almost all of them come with max and average speeds and can store two wheel sizes. They also almost all have trip counters (the BC1200 has two - so you can use one for total fuel mileage, and the other for map-work, for instance). I find a stopwatch feature is handy for certain road-sections. The BC1200 also allows you to set the odometer with a starting value (which is handy for recording a more accurate picture of the cars total mileage...)

 

Erm, what else? I like the BC1200 for its easy to use buttons (one on top, one underneath - handy when gloved-up). I also found its mounting bracket pretty easy to adapt for the car...

 

The only issue that is not so easy to resolve is lighting for nighttime use - I quickly became so dependant on the bike comp for my speed reading, that I became quite 'lost' when I first used it at night. Some comps do come with a backlight - but I don't know of any that don't time out after a few seconds - personally I use an LED torch mounted on my Road Angel to illuminate the comp - but I'm planning to rig up a dedicated LED sometime inthe future...

 

HTH - if you need any further clarification or ideas, let me know...

 

Keep BC free and open for ALL. Membership No. 43xx

 

Alcester Racing 7's Equipe - 🙆🏻

 

Alcester-Racing-Sevens.com

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Yes they have - but IMHO, it's a pain in the arse.

 

Various reasons including (but not limited to...):

 

i) Calibration - extremely easy when wheel mounted -you just push the car forward one wheel revolution (using the valves as markers) and measure the distance. With the prop you've got to do this and some calculations (ok, not complicated) regarding the diff ratio.

 

ii) With wheel-based sensors (assuming you use the front), you won't get false readings due to wheelspin etc. The front tyres also tend to wear down far less quickly than the rears - so the accuracy of the readings will be more stable over a period of time (noting, however, that a few mm less in tread-depth doesn't make that much of a difference to the rolling circumference).

 

iii) As long as you have cyclewings instead of clams, you've got a ready-made mounting point for the sensor - it will certainly be trickier (IMHO) to mount the sensor underneath the car somewhere.

 

OTOH, you don't need to worry about wheel balancing of whether your wheel actually has a magnet on it at all (handy if you borrow some rubber for trackdays) - you still have to measure the rolling circumference though...

 

Keep BC free and open for ALL. Membership No. 43xx

 

Alcester Racing 7's Equipe - 🙆🏻

 

Alcester-Racing-Sevens.com

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One other point worth noting with the Sigma range - the rear protruding body section is almost identical in size to the rocker switch cut-outs on teh Caterham dashboard. If you have a spare switch that you don't use (heater 🤔) it is possible to mount the Sigma in the hole - the contacts can be made using small pieces of foil tape sandwiching the wires to the edges of the hole.

 

The BC1200 switches are also better to use than the BC800 - they seam to need a little less pressure.

 

Stu.

 

 

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But to bang another of my favourite drums...

 

...I really do prefer having my most important instruments mounted above the scuttle - I find that (especially when wearing a helmet - for aeroscreening), I don't see much below the scuttle line - and if you've got to look away from the road to see the bike speedo, you might as well (apart from the accuracy issue) use the conventional one...

 

The following picture here shows more or less what I'm on about - even though the sigma is not actually in its mount (click small image for full size...)

 

YMMV - regds!

 

Keep BC free and open for ALL. Membership No. 43xx

 

Alcester Racing 7's Equipe - 🙆🏻

 

Alcester-Racing-Sevens.com

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Myles,

 

You're a star - thanks for providing these instructions. Have had my BC1200 for a few weeks, but haven't got round to fitting it as I couldn't work out where to fit the sensor.

 

One car - 1400 Supersport with 6 gears and clamshell wings. *smile*

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Why, thankyou *biggrin*

 

I popped into Halfrauds today - and yep, they do have the Sigma stuff - I was tempted by the BC1600 as an upgrade to the 1200, but couldn't justify it - all it really adds is the ability to track the mileage on two sets of wheels rather than having it all lumped together into one figure as on the 1200...

 

 

 

Keep BC free and open for ALL. Membership No. 43xx

 

Alcester Racing 7's Equipe - 🙆🏻

 

Alcester-Racing-Sevens.com

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John D,

 

I'm currently attaching one to the inboard CV joint on my dedion. This uses the locking tab for the diff bearing adjustment to mount the sensor. Just use a cut down "L" bracket from B and Screwit and a nut and bolt. Easy to get to just remove the wooden boot floor.

 

Yes it will over-read when you wheelspin off the line but so does the normal speedo. The main reasons I like this route are everything is hidden and no need to worry when you swap the wheels around.

 

Ian

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Thanks Ian, Myles

 

I think I will have a go with fitting to cv or propshaft, just to simplify and shorten the wiring trail. Re the gearing, I had assumed that I would simply need to measure the distance travelled between revolutions of the selected shaft, and that if this was taken over say 5 or 10 revolutions I could get this fairly accurate. A long flat straight bit of road (local Industrial estate), steel measure and the top off the gearbox tunnel should do the trick. I'll try it and see.

 

Regards, John

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You can get replacement sensors from Maplin - they sell them as reed switches for domestic window alarms for about £2.

 

If you mount the sensor/magnet on the prop, do you run into problems with the frequency of the signal, which will be 3-4 times the rate of a wheel based unit?

 

Oh, and do not be tempted by a wireless unit - they cannot handle the speed required and the range (not to mentionRF interference) is inadequate.

 

Gordon

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Hmmm, has anyone got any advice as to where to mount the wheel sensor on a car with FLARED wings? Can't really find an obvious mounting point.

 

 

One car - 1400 Supersport with 6 gears and clamshell wings. *smile*

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Just to add my 2 pence worth, I have a SPA digitial speedo, which is back lit, sits on the scuttle, has a tiny magnet for the front wheel, and is easy to use with a dedicated control button that is separate from the unit. I think I have debated the cost issue with Miles before of the SPA solution, but I agree with him that you really do need a back light and scuttle mounting is the way to go.

 

g

 

Superlight R #41

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Will there be much vibration if the magnet is mounted on a driveshaft ? It seems to me to be the best place because it rotates 1:1 with the wheel (unlike the propshaft) and as Ian says there are no worries about swapping wheels around.

 

John - when I've fitted these to my pushbikes I just measure the circumference of the wheel with a tapemeasure and use that as a starting point. I then double-check this against a straight piece of road of a known length (large scale o/s maps are good for this) but its always close enough not to need correction.

 

Nick

Red and Black 1.6K supersport

visit Carrotland.co.uk

 

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