Registered Address: Abercrave, Swansea SA9 1SQ
Company Reg. No 1200130  VAT Reg No. GB234519175
Tel: +44 (0)1639 732213 & (0)1639 732299 Fax: +44 (0)1639 732238
Email:-  instruments@speedycables.com   or  cables@speedycables.com

What information is required to re-calibrate my speedometer?

 

Speedometers cannot just be changed from one vehicle to another. They only read accurately when used on the unmodified vehicle for which they were originally calibrated. 

Even when used on the original vehicle, any changes that may have been made to the wheels, tyres, gearbox or other related parts can seriously affect the speedometer readings to the extent that the vehicle will fail to pass an SVA test or may result in a speeding fine. In this case, the speedometer will need to be re-calibrated.

To ensure that your speedometer reads accurately when fitted to your particular vehicle, we will need to calculate the required "revolutions per mile" >>>>

For calibration of a new instrument, or re-calibration of an existing instrument, we will need you to provide the following information from your vehicle...

(1) Take the measurement from the centre of the hub of a drive wheel to the ground, with the tyre pumped to normal pressure.

ANSWER:(1)__________ distance in Inches

(2) Put a chalk mark at the bottom of the measured wheel also marking on the ground where it meets.   Push the vehicle forward one revolution of the chalk mark and record the distance travelled

Answer:(2) __________ distance in Inches

(3) Now disconnect the speedometer and place a cardboard arrow on the end of the protruding inner speedometer cable.

Put a chalk mark at the bottom of the measured wheel and then push the car straight forward (with gear in neutral), counting exactly 6 revolutions of the wheel, whilst a partner counts the number of times that the arrow on the cable revolves.

ANSWER:(3)__________ number of turns of the cable. (N.B. include parts of a turn e.g. seven and a quarter turns)

*  DO NOT DO THIS BY JACKING UP THE WHEEL AS THIS GIVES COMPLETELY FALSE RESULTS *

Now send us the values that you recorded for Answer(1), Answer(2) and Answer(3) above.