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  1. #1
    Join Date
    Jan 2017
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    Mansfield, Notts
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    90

    Speedometer 8 DPC switch calibration

    The rear tyre size on my Cobra is 255 50 R16 and almost obsolete! £400 each for Michelins! I want to change to a more popular size but this will mean the speedometer will need to be re-calibrated.

    I'm looking for installation and calibration information for an 8 DIP switch speedometer but I have only found 10 DIP switch information. I'm not sure who the manufacturer is as there are no names on the speedometer.

    I was told it might be a 4" Smiths speedometer but after emailing Caerbont Automotive Instruments they have said it isn't one of theirs and they can't help me.

    I would think the Speedometer is probably about 26 years old if it was new when my car was built in 1993.










  2. #2
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    Sep 2009
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    Leeds
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    2,899
    what about these tyres fro North Hants:

    https://www.ebay.co.uk/itm/2555016-2...E/332624822355

    V rated, so not sure if fully suitable, i've got Z rated on mine - same size as you, and as you say replacements are bloody expensive.

    rgds
    Gary
    Conny - A Carnival Red Metallic (paint code Ref: Jag CGG/1811) Southern Roadcraft V8 ( SRV8 ) with 383ci stroker chevy.

  3. #3
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    Jan 2017
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    Mansfield, Notts
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    Quote Originally Posted by nealgs View Post
    what about these tyres fro North Hants:

    https://www.ebay.co.uk/itm/2555016-2...E/332624822355

    V rated, so not sure if fully suitable, i've got Z rated on mine - same size as you, and as you say replacements are bloody expensive.

    rgds
    Gary
    Yes I've seen those and what was on the car when it was new. 2 of those are going to be over £400. Currently got Bridgestones on all round and they are 10 years old and I can see small cracks so they all want changing. I'd sooner keep the same tyres all round. You can get 245 45 R16 Toyo Proxes for about £95. I can change all the tyres for under £400.

  4. #4
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    couldn't imagine 245 on the front, my steering is heavy enough with 235 lol (no powersteering).

    The 245/45 aren't going to fill the arch as well either - 5% difference in circumference.
    Conny - A Carnival Red Metallic (paint code Ref: Jag CGG/1811) Southern Roadcraft V8 ( SRV8 ) with 383ci stroker chevy.

  5. #5
    Join Date
    Oct 2009
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    Tavistock, Devon
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    Could always try here. This is for a pair.
    https://www.ebay.co.uk/itm/2x-SUMMER...4AAOSw~Ndc1ILe

    Noticed you need 50's not 55's though.
    Last edited by Murray; 10-05-19 at 11:59 AM. Reason: tyre size
    Cheers,
    Murray


    That's the trouble with you Sailors, long hair, quick zips and, Oohh, look at the size of that!!

    If I agreed with you, we'd both be wrong.

  6. #6
    Join Date
    Sep 2009
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    Leeds
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    they are 19" tyres to Murray
    Conny - A Carnival Red Metallic (paint code Ref: Jag CGG/1811) Southern Roadcraft V8 ( SRV8 ) with 383ci stroker chevy.

  7. #7
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    Tavistock, Devon
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    DOH! so they are sorry, put in 16's and didn't look properly!
    Cheers,
    Murray


    That's the trouble with you Sailors, long hair, quick zips and, Oohh, look at the size of that!!

    If I agreed with you, we'd both be wrong.

  8. #8
    Join Date
    Jan 2017
    Location
    Mansfield, Notts
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    90
    Quote Originally Posted by nealgs View Post
    couldn't imagine 245 on the front, my steering is heavy enough with 235 lol (no powersteering).

    The 245/45 aren't going to fill the arch as well either - 5% difference in circumference.
    think ZR a V rating are pretty much the same ?
    I have 225 50 16 on the front though I have fitted PAS. 245 45 16 give a tyre diameter of 627mm and 255 50 16 a diameter of 660mm so a difference of 33mm on diameter not sure you'd really notice the extra 16.5 mm clearance between tyre and wheel arch?

    I did ask Image about 17" rims just for the rears so I could use 255 45 17 tyres as they are still a reasonable price. Image haven't made that style for over 20 years. The claim they can make any style they have ever produced, except mine ! They changed casting suppliers and never had the moulds returned. I personally prefer this style to the Halibrand replica wheels they make.
    ICobra wheel.jpg
    I

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