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Installing a bicycle computer on my motorcycle

Discussion in 'Modifications and Projects' started by Gilligan, Nov 29, 2006.

  1. This post describes my experience of installing a bicycle computer on my Spada. No, it's not as silly as it sounds. :p

    I wanted to put a small digital clock on my bike for the obvious reason of being able to tell the time without digging around for my phone (I don’t wear a watch). This got me wondering whether it would be possible to install a digital bicycle computer on my bike which would give me a whole heap more useful info other than the time :-k . A bit of forum and google searching and it was pretty apparent that I was no inventive genius as many people have done this, so armed with some info, money and a spare Sunday arvo I decided to do it.

    Common wisdom in the infallible world of cyberspace was that Sigma bike computers were the best for dealing with the higher speeds of a motorbike (as opposed to pedal+lycra power), so after a bit of research I decided to go for a Sigma BC 1606L. It has loads of features, notably a maximum speed function and a backlight for night viewing. I picked one up at Cecil Walker Cycles (along the Elizabeth Street motorbike strip) for what I think is a great price of $59.95. They also sell a wireless version but at nearly double the price I decided I’d live with a wire running from the sensor. Not as neat, but I’m $55 better off.

    The installation was surprisingly straight-forward. The only extras I needed were some epoxy and some cable ties. The basic procedure went something like this....

    First I needed to work out where the speedo would sit. I had a good spot for it on my right bar so I attached it there using the supplied hardware (a rubber o-ring!). I then threaded the sensor through the bars and down to the right fork as I decided to put the rotating magnet that goes past the sensor on the disc brake (the inner part of the disc assembly, not the actual disc!:facepalm: ).

    The supplied magnet that normally attaches to a bicycle wheel is not suitable for a motorbike so I cut the small bar magnet out of the plastic housing and after lining everything up, I used epoxy to attach the magnet to the brake disc. It was located so the magnet would pass within 5 mm of the sensor as the wheel turned and obviously in a spot that wouldn’t interfere with the brake caliper. If you do this make sure you clean the magnet and the spot on the disc you will be attaching the magnet to with metho or some other solvent to ensure a good, durable bond by the epoxy.

    The sensor attached to the fork, again with one of the supplied o-rings, and the job was almost done. I used cable ties to neatly secure the wire from the sensor to the speedo and I was done :grin: .

    After programming the right wheel circumference in and letting the epoxy set I was ready to go. The result? It worked perfectly straight off and hasn’t missed a beat yet. All up the installation took less than an hour. I’ve had it up to 113 km/h so far and it worked fine. The epoxied magnet is very secure and I’m confident it won’t fly off at high speed :eek:hno: .

    Some pictures of the final installation are below.

    Speedo installed on the bar

    Close-up of the speedo

    Magnet epoxied to the brake disc

    The sensor attached to the fork

    nice write-up, thanks :)
  3. and you have to be careful about your speedo.
    I attatched a digital clock to my bike and then it got stolen within the 24 hours I had it.
    why would you need that computer though?
    you have a speedo that tells you haw fast you are going
    you have an odometer to tell you your distance.
    Not a bad idea if the gauges are broken though
  4. Great post :grin:

    I have been looking into this as I know the speedo on the GS is at least 10km out at 100km but don't know by how much at slower town speeds.

    Think I will have to invest in one now. :)
  5. Good writeup.

    As for the 'need' for a cycle computer, it's safe to say that all bike speedos are inaccurate. Mostly, they read on the fast side, which is OK for speed cameras. But unless you get it checked, you'll never know.

    Aside from the speed and odo functions, they also tell you things like average speed, riding time, countdown timer (enter in distance to destination and it will tell you how far to go and how long based on current speed) and other functions.

    The only problem that I had with the Sigma Sport range is that the mounts don't cater for non-tubular handlebars. I ended up making some brackets that bolt onto my handlebar clamps. I actually made two - the second for a Garmin Etrex GPS.

    When fitting one of these CCs, it's probably best if you can calibrate it against a GPS. Again, there are heaps of threads in here about this stuff.
  6. ..errr it wasn't fitted for the speedo function, it was fitted to supply a clock; I wanted to put a small digital clock on my bike for the obvious reason of being able to tell the time without digging around for my phone (I don’t wear a watch). :roll:

    Good write up and exceptional pictures, UB. This is the first of many discussions of this matter that actually makes me think it's worth while me doing it (for the same chronological reasons)
  7. I was surprised to find out that around town my analogue speedo is almost exactly right. It begins to overestimate my speed at 100+ km/h.

    Calibration of the digital speedo is easy - put a paint, chalk or other ink line across your front tyre and roll the bike along so that it leaves two imprints on the ground. Measure the distance between the two marks and there is your wheel circumference that you program in. Typical circumference is 18-1900 mm. Even if you muck up this measurement by say 18 mm (a fair bit really) your speedo is still only off by 1%, so it's a pretty reliable technique - if you can work a tape measure :p Don't know if a GPS would be better or worse for calibration.
  8. But not accurate.

    When I did mine it was still out by one or three kays, so some fine tuning on a local stretch of flat, straight and largely unused road got it spot on.

    I calibrated mine against two criteria - speed and distance. When both the CC and the GPS's trip meter were reading the same and that the speed, as best as I could get it to be constant (hence this particular road that I used), then I was happy.

    When I sold my barge I left the Sigma Sport on it. The Blackbird needed one so I settled for an Echowell F7 CC. When I input the same circumference setting as the Sigma used I found it to be a kay or so out. Just had to do the same fiddling.

    Thing is, when I got my first CC it was for the same reason as the OP - I needed a clock as the barge didn't have one. None of the local shops (Tandy, Kmart, etc.) had anything that looked halfway decent. It was on aus.motorcycles newsgroup that I was pointed in the direction of a CC.

    The Echowell has a limited trip meter. It only goes to 999 km. (Its overall odo goes to 10,000 km I think). Whatever, it reset its data when it rolled over to 0 km last weekend during our 3 day ride. Luckily the GPS data had not been reset. I'll use the CC to record daily info and the GPS for the overall info for a weekend ride.
  9. Brilliant idea

    only problem with calibration method is that it will out when you corner as the circumference of the side of the tyre will be less than centre.

    Accurate in the centre though.

  10. Magnets don't like heat, how hot do the discs get where the magnet is placed?
  11. Dunno. But given that they're out there in the airflow and that the hub of the wheel can act as a heatsink, I doubt that it's a problem.

    I currently have mine glued to one of the disc's mounting bolts. Haven't had any issues to date.

    Anyway, if magnets have problems with heat, how do motors with permanent magnets cope?
  12. [/quote]

    Then you get on it and put pressure on the tyres and it becomes a bit more inaccurate and then you pump your tyres up and it's a little bit more out, and before you know it your speedo is out by 5-10% :wink:
  13. It's a start. From there you fine tune or calibrate it against either a GPS, or the odo reading against say, two 5 km posts. Reset the trip meter at the start and finish of the 5 km stretch. See what the reading is, recal the CC and repeat. Of course, it's much easier with a GPS.
  14. I was test riding a bicycle the other day and the store assistant said they use these on motor bikes though he didnt know what tops speeds they read. What is the maximum speed these things read to? Wont the distance the magnet is situated from the outside diametre of the tyre or axle have to be calculated into the equation?
  15. Earilier Sigma Sports were good for 300 km/h. Later ones only run to 200 kays, apparently. My Echowell F7 is allegedly good to 200 km/h. But occasionally it glitches and I see max. speed readings of 340 km/h. Dunno why. RoderickGI, I think it was, on a Netride recently said that if the magnet's sitting over the sensor when parked, it could cause an erroneous reading to occur.

    As for its top speed reading, I think that it's largely academic. I bought mine for two reasons; to get something with a clock and a basic trip computer and to have a speedo that was accurate for normal road speeds.

    As for the position of the magnet, as far as calibration goes, it doesn't matter whether it's near the centre of the wheel or on the rim. It counts revolutions. Some have said, though, that as the relevant velocity diff between magnet and sensor changes depending on where the sensor's located, that this could make a difference.

    I don't know if this is the case or not. I've tried both, and it didn't seem to make any difference when I checked the speedo against my GPS.
  16. Info I found said that Sigma brand computers read much higher speeds than other brands. I've had it up to 140 kph (on a private drag strip of course!) and it worked fine - my Spada won't go much faster so can't vouch for higher speeds, but my understanding is that it should go much higher than this.

    You don't need to measure where the magnet sits relative to the outside of the rim. You program into the computer the circumference of your tyre, i.e. how far you go with one wheel revolution. Each time the magnet goes past the sensor is one revolution, regardless of where it is situated on the wheel.
  17. Useful if you have a new bike :idea:

    Cut the speed sensor and use the cycle meter instead.. then sell at low kays :LOL:
  18. Apart from being unethical (who am I to judge :LOL:) some late model bikes have the Speedo sensor going to the ECU. If you "cut it" it will put it in limp home mode, run like crap and might limit RPM.

    I found this out the hard way, spliced into a speedo sensor wire (on a car) for an ADL install, started calibration and just as it was about right, went into limp mode. Had to splice into the ABS wheel speed sensor!

    Some early carb bikes might have a problem too! Some are limited to 180kph (jap imports) and depending if the sensors polarity, disconnecting it make trigger it into a false speed limit. Imagin hitting a speed limiter in the middle of power band in first gear- might be a but scary!
  19. Wireless Cycle Computers and Interference

    I'm looking at a Sigma Sport BC16006L. It comes in two flavors - wired and wireless. I've read in the past that the wireless versions are susceptible to intereference from a motorcycle's electrical system. I was wondering if anyone here has fitted a wireless BC to their bikes and found that it works/doesn't work.

    The alternative is the wired version which is cheaper, but the cable may not be long enough. On previous models that I've owned I had to extend the cable to make it reach the front disc where I mounted the magnet.

    I currently have an Echowell F7 BC. But it plays up, with its readings sometimes being corrupted or it gets glitches and starts reading incorrectly. Eg. it currently has a max speed reading of 347 km/h. Apart from the fact that the 'bird doesn't go that fast, the Echowell's top speed is 200 km/h. So, I'd like to replace it with a Sigma Sport which I've found to be reliable.
  20. hey great work- i had one installed on my pocket bike and it gave me speed / distance / etc now i know my 49cc bike goes 39.8km/hr - heeheee :cool: :cool: