Hitchcocks Forum

A while ago the Smiths chronometric speedo (a real one) on my Redditch/AVL hybrid stopped working after 3000 miles. I traced the problem to a stripped (Indian) drive unit at the rear wheel, which I shrugged off as poor quality (they're cheap enough almost to be disposable items), fitted a replacement and all seemed well. The speedo has sinced stopped working again, and this time moving the bike with the speedo cable disconnected still shows the cable to be turning, the speedo itself has now stopped working.



Having searched the web sites of a number of speedo repair specialists (how come Nottingham has so many?) I found that at least two of them are warning against imported drive cables with inner cables which are too long. When the cable is fitted the excess inner length puts excess stress on the drive and/or speedometer innards, resulting in failure of the drive and/or speedometer itself.



The inner cable is supposed to protrude from the outer at the instrument end by NO MORE THAN 7/16" I checked the protruding inner cable on mine, 9/16" - bingo.



http://chronometrics.co.uk/Cables/cables.html

http://www.gaggs.co.uk/html/cables.html



To anyone who is about to fit an expensively restored chronometric to that restoration project or even just replacing a cable - CHECK!!! This info was new to me, if it saves someone else some needless expense I hope it helps. Meanwhile I have a trip out to my nearest speedo repair man tomorrow.



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Sorry there was a < missing from the < br > between the two links, I can post them again if anyone can't get them to work. A.

Thanks Adrian. This is useful info. I'll check mine before I take it out again. I've seen the price of replacement chronometric speedos!

Tough luck Adrian, but don't beat yourself up, it's an easy mistake to make. The longer cable is actually intended for the later Smith's Magnetic instruments so they are not completely wrong!

REgards, Mark

Hi, it may still be the rear wheel drive as it will turn the cable but not with the load applied by the speedo. Quick way to check is to stick inner cable into speedo a rotate with you fingers it should click and the needle jerk. Vince

I did check the speedo off the bike, it had definitely failed, so I took it to see a specialist repairer in Littlehampton today. He noted that it was a ex-police bike instrument (they insisted on chronometrics for quite a while after the buying public had to make do with the magnetic type) which apparently had a slightly different cable entry. It had been modified for general use but had had too much metal removed, making the effect of the over-long inner cable worse.



The good news is that it should be repaired in two or three weeks and it's also being re-calibrated for better accuracy with the 100/90 x 18 rear tyre I'm using. The existing calibration was for a different sized tyre, making the speedo read a bit slow - not clever with all the speed cameras around.



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