Home page

Loading....
Please wait
Good  luck with your project’...  Enjoy your classic motoring...
Fixed price repairs are based on the assumption that unit/s received
 are
‘original & complete’... a surcharge may be applied to cover
missing  parts etc...  If in doubt send in the unit for inspection
If  you  found this web site via a ‘search engine’ please
 check that you are looking @ the
latest version... click here
Tip! Press F11 for a full page view @ 1024 x 768 screen resolution  
press F11 again to revert to normal view  ( I. E.  browser’s only)
Mileage correction
Clocks
Other services
Post & packing
Contact details
Speedos
Rev counters
Jaguar XK 120 ( 1948 / 54 )
117.1 M
Parts Order E-Mail Link
Payment options
Payment options
Payment options
Payment options
JDO Instruments
Classic Car Instrument Repairs ( Est 1963 )
Fixed price repairs for most British & European Classic Car Instruments
48hr service  
available... Why pay more & wait longer ! No UK vat
Tele: (UK)  01535 672125    Mobile / SMS:  07831 886545
Please check the  FAQ’s page  BEFORE ringing / emailing... thank you
Speedo Calibration... Calculation page

       To calculate the calibration required ( wheel turn method ) use the following formula  
      ( 6336 ÷ A )  x  B  =  TPM ( cable turns per mile )
A = Circumference of a fitted tyre in inches* ( Cross-ply )  for Radial  multiply A x  0.98 ( ie. deduct 2% )
B = number of speedo cable turns for 20 turns of one wheel ( 10 turns for LSD )
      Typical example :
A = 80 for Cross-ply  or 78.4 for Radial   B = 14.5 speedo cable turns
      ( 6336 ÷ 78.4 ) x  14.5  =  1172 TPM ( Radial  ) or ( 6336 ÷ 80 ) x 14.5 = 1148 TPM ( Cross-ply  )

       If using the road test method the following formula applies ...
      ( A  ÷  B )  x  the present calibration = TPM  where A =  your indicated distance  &  B =  true distance
      Typical example :  A = 9 miles & B = 10 miles.. if  the present calibration  is say 1000 TPM
        the required calibration would be ( 9 ÷ 10 )  x  1000  =  900 TPM  
       For TPKM ( cable turns per kilometre ) multiply TPM x 0.621        
       
*Centimetres x 0.393 = inches                                                                Continued on next page

Scimitar GTE
Re-Calibration surcharge
Re-Calibration surcharge
Re calibration surcharge