Home page

Please wait
Fixed price repairs are based on the assumption that unit/s received
‘original & complete’... a surcharge may be applied to cover
missing  parts etc...  If in doubt send in the unit for inspection
Good  luck with your project’...  Enjoy your classic motoring...
If  you  found this web site via a ‘search engine’ please
 check that you are looking @ the
latest version... click here
Mileage correction
Other services
Post & packing
Contact details
Rev counters
Jaguar XK 120 ( 1948 / 54 )
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:   01535 603570 / Mobile: 07872 071512
Please check the  FAQ’s page  BEFORE ringing / texting / emailing
Information required to Check / Re- Calibrate a Speedo
                                                                                                                    print off a copy & enclose with your order...    
*Jack up just 1 Driven wheel  Measure the Circumference of the fitted tyre in inches  = _______  cms  = _______
Remove the Speedo...make up a cardboard pointer or similar & fix it to the end of the exposed inner speedo cable
Put a chalk mark etc on the edge of the tyre & the ground ...
Now  turn the
‘Jacked up’  wheel 20 turns forward ( out of gear )
& count the number of turns the speedo cable makes = ___________  to the nearest 1/8 ( eighth ) of a turn

* The above assumes a Normal diff unit ... if the car is fitted with a Limited slip diff  ( LSD)...
Jack up
 Both driven wheels  & turn one wheel 10 turns forward ( out of gear )
take up the ‘LSD’ slack first  ie. until the OTHER wheel starts to turn  ( approx ½  turn  )  
Please state the FULL tyre size _____________________    & type eg.  Radial  /  Cross-ply  ( delete one )

However if your car is on the road & running ask a friend etc to pace you in another car *  with a speedo known
to be ok... ie. set the
Trip on both cars to zero ... Travel approximately 10 miles / 16 Km & advise both readings
eg. True distance = _______  Your cars indicated distance = ________  to the nearest 1/10 ( tenth ) of a mile / Km
*Or use a ‘reliable’ Sat-Nav  ...ie.  Most classic cars have a more ‘upright’ windscreen’ which can limit the satellite view...
Continued on next page  
Calculation page
Calculation page
Calculation page 1
Re-Calibration surcharge
Re-Calibration surcharge
Re calibration surcharge