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Thread: Speedometer adjustment

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    Speedometer adjustment

    How is the BJ8 speedometer recalibrated when the rear end has been replaced with 3:54 gear ratio. I know that it can be sent off and calibrated. What is the actual method used to recalibrate it. My son used his GPS when he was here from England and it appears I am about 8-9 mph low on the speedometer now. Would seem that a constant speed drill could determine a fixed speed (say 60 mph) which would correlate to the old ratio and then adjusted to read higher mph at the same drill rpm if there is a simple adjustment? Don't these things work off a magnetic coupled disk(eddy current) or is there an actual gear that must be changed?

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    Yoda John Turney's Avatar
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    Re: Speedometer adjustment

    The speed works off a magnetic coupled disk, but the odometer uses gears, so if you adjust the speed the mileage will still be off. I believe the speedometer can be adjusted by adjusting the spring inside, but it is usually left to professionals. there is, however, a manual at https://www.szott.com/lotusinfo/Smit...edo_repair.pdf .
    John, BN4

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    Re: Speedometer adjustment

    After I installed a 3.5 diff I had a speedometer shop build a reduction coupling. He measured the number of tire rotations in a given distance and took it from there. The coupling lives behind the dash.

    Best--Michael Oritt
    1954 Austin-Healey 100 Le Mans
    1959 Elva MK IV Sports Racer
    1961 Ginetta G4

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    Re: Speedometer adjustment

    Quote Originally Posted by Michael Oritt View Post
    After I installed a 3.5 diff I had a speedometer shop build a reduction coupling. He measured the number of tire rotations in a given distance and took it from there. The coupling lives behind the dash.
    Do you recall how much you paid?
    Patrick
    '67 Metallic Golden Beige/Red
    Owned since '72

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    Re: Speedometer adjustment

    About $150.00 probably 12 years ago. The name of the business was Bob's Speedometer shop just south of BWI Airport.

    Best--Michael Oritt
    1954 Austin-Healey 100 Le Mans
    1959 Elva MK IV Sports Racer
    1961 Ginetta G4

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    Re: Speedometer adjustment

    Quote Originally Posted by Michael Oritt View Post
    About $150.00 probably 12 years ago. The name of the business was Bob's Speedometer shop just south of BWI Airport.
    thanks. I just spent almost $300 to have mine rebuilt and calibrated.
    Patrick
    '67 Metallic Golden Beige/Red
    Owned since '72

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    Re: Speedometer adjustment

    An elegant solution is to consider an electronic conversion. This makes calibration easy. See my earlier posting.

    https://www.britishcarforum.com/bcf/...-Tacho-upgrade

    Another option is to use a GPS driven cable drive; this is in final stages of testing by Classic Innovations. This is similar to the Speedy solution but GPS driven.

    https://www.classicautoinnovations.com/#!blank/cvdf

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    Re: Speedometer adjustment

    Re: the GPS cable drive this is really cool, not sure why no one has done this yet. Not only does this correct for gear changes and the rolling differences between inch/bias ply and metric sized radial tyres but it seems it could eliminate the need for the often trashed and typically expensive angle drives at the trans/O.D.

    "...This is the cable connection to the transmission end found on most British classics."

    "For 12v NEGATIVE GROUND vehicles only at this time."
    "Wally" Casten
    British Cars: 1956 Austin-Healey 100 BN2 previously owned by my father
    British Bikes: 1997 Triumph Speed Triple (120,000+ miles)
    The Dark Side: 1987 Porsche 911 3.2 Carrera, 1982 BMW 320is

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    Yoda HealeyRick's Avatar
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    Re: Speedometer adjustment

    Wally,

    I'm a beta tester for the Classic Speed unit. As you mentioned, it nicely compensates for varying tire sizes. Where it really shines is for those who've converted their Healey to a 3.54 rear end or who have a Toyota tranny (or even a Ford, like me). I think it's the best option for those wanting to keep their stock gauges. As far as positive earth goes, my bugeye has no radio or any other device sensitive to ground, so it remains positive. But the Nasty Boy has radio, electric fan, the Classic Speed and has been converted to negative earth. If someone wants to incorporate a modern electrical device in their car, it doesn't take much effort to switch the ground and unless you're competing in concours, I don't see any advantage to keeping it positive earth.
    Rick

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    Re: Speedometer adjustment

    A GPS driven cable drive for speedo, Please forgive me for being a real smart alex, Why don't you just hang a GPS unit in the car. I constantly check mine to compare mph with the original speedo. And if you do use your car for shows and concours you don't upset the originality of the car. Just remove the GPS unit for the day.
    By the way has anyone considered the electrical load on their original Healey electrical system using any GPS receiver. You might notice the the twin auxilary power plugs mounted to the shelf of my Healey. See pic.
    Those are for the GPS and the Ipad/cell phone. Of course my car has an 85 amp alternator, with custom wiring harness and two 8-pole fuse boxes. Just saying, better check your electrics.
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    "...you really can't restore a car in 10 days. I don't want to watch a race where people have to restore it in a week. It's not going to drive, and those cars never work. In real life, it takes years to get it right. " Jay Leno.

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    Yoda HealeyRick's Avatar
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    Re: Speedometer adjustment

    Quote Originally Posted by vette View Post
    A GPS driven cable drive for speedo, Please forgive me for being a real smart alex, Why don't you just hang a GPS unit in the car.
    Because I like to keep my car looking all original
    Rick

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    Re: Speedometer adjustment

    Quote Originally Posted by vette View Post
    A GPS driven cable drive for speedo, Please forgive me for being a real smart alex, Why don't you just hang a GPS unit in the car...
    Quote Originally Posted by HealeyRick View Post
    Because I like to keep my car looking all original
    Good question. For me, I work on a computer all day long at work every day, then I come home and here I am on a computer typing this. Part of why I have the 100 as well as the other "analog" cars is, well...the last thing I want is to get into my Healey and have to look at another computer screen. But I do understand why and respect why you and others use them in their Healeys. Also, I guess I'm just anal, but I'd like having the physical odometer on the car logging the correct mileage that is being put on for maintenance, fuel mileage and general tracking records.

    This drive seemed like a nice middle ground, whereby a computer is accurately handling a task but totally behind the scenes. Not sure if I want to convert the whole car to negative earth just to use it, but I will consider it Rick, thanks.

    Back when I had my speedo rebuilt some years ago that shop said they could split the cable and put in a "gearbox" coupling ala what Mr. Oritt indicated (great driving at the PVGP Michael, saw you there!). They wanted a brand new cable so I bought one at that time but never had it done since I planned on doing the 3.54 gears. My speedo/odo has always been way off in this car, as in reading 20% low, now with the 3.54 gears it's going to be even further off if my logic is correct.
    "Wally" Casten
    British Cars: 1956 Austin-Healey 100 BN2 previously owned by my father
    British Bikes: 1997 Triumph Speed Triple (120,000+ miles)
    The Dark Side: 1987 Porsche 911 3.2 Carrera, 1982 BMW 320is

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    Re: Speedometer adjustment

    Good point Walt. I had my speedometer rebuilt and "recalibrated" some years ago and, while the speed is as accurate as ever, the odometer is quite off.
    John, BN4

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    Re: Speedometer adjustment

    The speedometer on my '85 Toyota Camry that i bought from[DELETED] is calibrated up to 130 mph. Is this because a) it is really capable of going 130 mph b) it provides for a nice, symmetrical layout, with 65 mph being straight up at the top. c) the manufacturer thinks that by calibrating it up to 130 mph, I'll think I'm in a sporty car (a psychological ploy)? By the way, my boyfriend's '83 Toyota Celica Supra speedometer only goes up to 85 mph.
    Anna
    Last edited by Basil; 07-29-2016 at 11:23 AM.

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    Re: Speedometer adjustment

    I am really interested in this device so I am going to wait until they come out with the production unit. I was going to go through the rolling distance measurement method and then sending it off to a rebuilder but I really like this concept. I have a retro radio unit that needs to be installed anyway so I will be taking a lot of dashboard "stuff" off anyway for that. The website seems to indicate there is a drive unit and an antenna for the GPS. Where did you place the GPS antenna in your car?

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