Reliable dials can make the world of difference in a classic car. Here's what you need to know
Instruments are your window into a car’s machinations. You glance at them often, so they must tell the truth as well as looking good. The durability of instruments can be extraordinary, those in cars half a century old or more often still functioning perfectly, but sometimes they need a bit of love.
The most likely candidate for attention is the speedometer, whose hairspring can weaken with age and cause the needle to over-read. Or dirt can build up inside, encouraged by oil travelling up the cable or using too much grease when fitting a new one, causing components to stick or the moving magnet attached to the needle to snag the rotating, cable-driven wheel so the needle attempts a second lap of the dial.
Some cars, most often pre-war or racing machinery, use a chronometric system in which the needle moves in precise jerks. Both types can be reconditioned, the chronometric type requiring particular skills of the clockmaking variety, and you’ll be amazed at how accurate a properly rebuilt speedometer can be.
Instrument faces can be recreated in the right font, the bezels rechromed, the needles repainted be it in white, black, DayGlo red or whatever else was original. If you have changed your car’s gearing, maybe by fitting a higher-ratio differential, recalibration will make your speedo read correctly. A dead clock can work again with modern internals; an old mechanical or current-sensing electronic revcounter can be converted to a modern voltage-pulse type, compatible with electronic ignition.
Such work might not be cheap, but the likes of Speedy Cables, Robert Fenn and Speedograph Richfield do a fine job. This writer has just made use of JDO Instruments for a speedo refurb; it was returned in tip-top shape and bang-on accuracy in just a week.
If your speedo reads 90mph when you know you can’t be doing more than 60, send it to a specialist. Driving a classic is so much more satisfying when dials don’t tell fibs.
Words: John Simister